// SPDX-License-Identifier: GPL-2.0
/*
 * DRM driver for PIXPAPER e-ink panel
 *
 * Author: LiangCheng Wang <zaq14760@gmail.com>,
 */
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/spi/spi.h>

#include <drm/clients/drm_client_setup.h>
#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_drv.h>
#include <drm/drm_fbdev_shmem.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_gem_atomic_helper.h>
#include <drm/drm_gem_shmem_helper.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_print.h>
#include <drm/drm_probe_helper.h>

/*
 * Note on Undocumented Commands/Registers:
 *
 * Several commands and register parameters defined in this header are not
 * documented in the datasheet. Their values and usage have been derived
 * through analysis of existing userspace example programs.
 *
 * These 'unknown' definitions are crucial for the proper initialization
 * and stable operation of the panel. Modifying these values without
 * thorough understanding may lead to display anomalies, panel damage,
 * or unexpected behavior.
 */

/* Command definitions */
#define PIXPAPER_CMD_PANEL_SETTING 0x00 /* R00H: Panel settings */
#define PIXPAPER_CMD_POWER_SETTING 0x01 /* R01H: Power settings */
#define PIXPAPER_CMD_POWER_OFF 0x02             /* R02H: Power off */
#define PIXPAPER_CMD_POWER_OFF_SEQUENCE 0x03    /* R03H: Power off sequence */
#define PIXPAPER_CMD_POWER_ON 0x04              /* R04H: Power on */
#define PIXPAPER_CMD_BOOSTER_SOFT_START 0x06    /* R06H: Booster soft start */
#define PIXPAPER_CMD_DEEP_SLEEP 0x07            /* R07H: Deep sleep */
#define PIXPAPER_CMD_DATA_START_TRANSMISSION 0x10
/* R10H: Data transmission start */
#define PIXPAPER_CMD_DISPLAY_REFRESH 0x12       /* R12H: Display refresh */
#define PIXPAPER_CMD_PLL_CONTROL 0x30           /* R30H: PLL control */
#define PIXPAPER_CMD_TEMP_SENSOR_CALIB 0x41
/* R41H: Temperature sensor calibration */
#define PIXPAPER_CMD_UNKNOWN_4D 0x4D            /* R4DH: Unknown command */
#define PIXPAPER_CMD_VCOM_INTERVAL 0x50 /* R50H: VCOM interval */
#define PIXPAPER_CMD_UNKNOWN_60 0x60            /* R60H: Unknown command */
#define PIXPAPER_CMD_RESOLUTION_SETTING 0x61    /* R61H: Resolution settings */
#define PIXPAPER_CMD_GATE_SOURCE_START 0x65     /* R65H: Gate/source start */
#define PIXPAPER_CMD_UNKNOWN_B4 0xB4            /* RB4H: Unknown command */
#define PIXPAPER_CMD_UNKNOWN_B5 0xB5            /* RB5H: Unknown command */
#define PIXPAPER_CMD_UNKNOWN_E0 0xE0            /* RE0H: Unknown command */
#define PIXPAPER_CMD_POWER_SAVING 0xE3          /* RE3H: Power saving */
#define PIXPAPER_CMD_UNKNOWN_E7 0xE7            /* RE7H: Unknown command */
#define PIXPAPER_CMD_UNKNOWN_E9 0xE9            /* RE9H: Unknown command */

/* R00H PSR - First Parameter */
#define PIXPAPER_PSR_RST_N BIT(0)
/* Bit 0: RST_N, 1=no effect (default), 0=reset with booster OFF */
#define PIXPAPER_PSR_SHD_N BIT(1)
/* Bit 1: SHD_N, 1=booster ON (default), 0=booster OFF */
#define PIXPAPER_PSR_SHL BIT(2)
/* Bit 2: SHL, 1=shift right (default), 0=shift left */
#define PIXPAPER_PSR_UD BIT(3)
/* Bit 3: UD, 1=scan up (default), 0=scan down */
#define PIXPAPER_PSR_PST_MODE BIT(5)
/* Bit 5: PST_MODE, 0=frame scanning (default), 1=external */
#define PIXPAPER_PSR_RES_MASK (3 << 6)
/* Bits 7-6: RES[1:0], resolution setting */
#define PIXPAPER_PSR_RES_176x296 (0x0 << 6)     /* 00: 176x296 */
#define PIXPAPER_PSR_RES_128x296 (0x1 << 6)     /* 01: 128x296 */
#define PIXPAPER_PSR_RES_128x250 (0x2 << 6)     /* 10: 128x250 */
#define PIXPAPER_PSR_RES_112x204 (0x3 << 6)     /* 11: 112x204 */
#define PIXPAPER_PSR_CONFIG                                           \
        (PIXPAPER_PSR_RST_N | PIXPAPER_PSR_SHD_N | PIXPAPER_PSR_SHL | \
         PIXPAPER_PSR_UD)
/* 0x0F: Default settings, resolution set by R61H */

/* R00H PSR - Second Parameter */
#define PIXPAPER_PSR2_VC_LUTZ \
        (1 << 0) /* Bit 0: VC_LUTZ, 1=VCOM float after refresh (default), 0=no effect */
#define PIXPAPER_PSR2_NORG \
        (1 << 1) /* Bit 1: NORG, 1=VCOM to GND before power off, 0=no effect (default) */
#define PIXPAPER_PSR2_TIEG \
        (1 << 2) /* Bit 2: TIEG, 1=VGN to GND on power off, 0=no effect (default) */
#define PIXPAPER_PSR2_TS_AUTO \
        (1 << 3) /* Bit 3: TS_AUTO, 1=sensor on RST_N low to high (default), 0=on booster */
#define PIXPAPER_PSR2_VCMZ \
        (1 << 4) /* Bit 4: VCMZ, 1=VCOM always floating, 0=no effect (default) */
#define PIXPAPER_PSR2_FOPT \
        (1 << 5) /* Bit 5: FOPT, 0=scan 1 frame (default), 1=no scan, HiZ */
#define PIXPAPER_PSR_CONFIG2     \
        (PIXPAPER_PSR2_VC_LUTZ | \
         PIXPAPER_PSR2_TS_AUTO) /* 0x09: Default VCOM and temp sensor settings */

/* R01H PWR - Power Setting Register */
/* First Parameter */
#define PIXPAPER_PWR_VDG_EN \
        (1 << 0) /* Bit 0: VDG_EN, 1=internal DCDC for VGP/VGN (default), 0=external */
#define PIXPAPER_PWR_VDS_EN \
        (1 << 1) /* Bit 1: VDS_EN, 1=internal regulator for VSP/VSN (default), 0=external */
#define PIXPAPER_PWR_VSC_EN \
        (1 << 2) /* Bit 2: VSC_EN, 1=internal regulator for VSPL (default), 0=external */
#define PIXPAPER_PWR_V_MODE \
        (1 << 3) /* Bit 3: V_MODE, 0=Mode0 (default), 1=Mode1 */
#define PIXPAPER_PWR_CONFIG1                         \
        (PIXPAPER_PWR_VDG_EN | PIXPAPER_PWR_VDS_EN | \
         PIXPAPER_PWR_VSC_EN) /* 0x07: Internal power for VGP/VGN, VSP/VSN, VSPL */

/* Second Parameter */
#define PIXPAPER_PWR_VGPN_MASK \
        (3 << 0) /* Bits 1-0: VGPN, VGP/VGN voltage levels */
#define PIXPAPER_PWR_VGPN_20V (0x0 << 0) /* 00: VGP=20V, VGN=-20V (default) */
#define PIXPAPER_PWR_VGPN_17V (0x1 << 0) /* 01: VGP=17V, VGN=-17V */
#define PIXPAPER_PWR_VGPN_15V (0x2 << 0) /* 10: VGP=15V, VGN=-15V */
#define PIXPAPER_PWR_VGPN_10V (0x3 << 0) /* 11: VGP=10V, VGN=-10V */
#define PIXPAPER_PWR_CONFIG2 PIXPAPER_PWR_VGPN_20V /* 0x00: VGP=20V, VGN=-20V */

/* Third, Fourth, Sixth Parameters (VSP_1, VSPL_0, VSPL_1) */
#define PIXPAPER_PWR_VSP_8_2V 0x22 /* VSP_1/VSPL_1: 8.2V (34 decimal) */
#define PIXPAPER_PWR_VSPL_15V 0x78 /* VSPL_0: 15V (120 decimal) */

/* Fifth Parameter (VSN_1) */
#define PIXPAPER_PWR_VSN_4V 0x0A /* VSN_1: -4V (10 decimal) */

/* R03H PFS - Power Off Sequence Setting Register */
/* First Parameter */
#define PIXPAPER_PFS_T_VDS_OFF_MASK \
        (3 << 0) /* Bits 1-0: T_VDS_OFF, VSP/VSN power-off sequence */
#define PIXPAPER_PFS_T_VDS_OFF_20MS (0x0 << 0) /* 00: 20 ms (default) */
#define PIXPAPER_PFS_T_VDS_OFF_40MS (0x1 << 0) /* 01: 40 ms */
#define PIXPAPER_PFS_T_VDS_OFF_60MS (0x2 << 0) /* 10: 60 ms */
#define PIXPAPER_PFS_T_VDS_OFF_80MS (0x3 << 0) /* 11: 80 ms */
#define PIXPAPER_PFS_T_VDPG_OFF_MASK \
        (3 << 4) /* Bits 5-4: T_VDPG_OFF, VGP/VGN power-off sequence */
#define PIXPAPER_PFS_T_VDPG_OFF_20MS (0x0 << 4) /* 00: 20 ms (default) */
#define PIXPAPER_PFS_T_VDPG_OFF_40MS (0x1 << 4) /* 01: 40 ms */
#define PIXPAPER_PFS_T_VDPG_OFF_60MS (0x2 << 4) /* 10: 60 ms */
#define PIXPAPER_PFS_T_VDPG_OFF_80MS (0x3 << 4) /* 11: 80 ms */
#define PIXPAPER_PFS_CONFIG1           \
        (PIXPAPER_PFS_T_VDS_OFF_20MS | \
         PIXPAPER_PFS_T_VDPG_OFF_20MS) /* 0x10: Default 20 ms for VSP/VSN and VGP/VGN */

/* Second Parameter */
#define PIXPAPER_PFS_VGP_EXT_MASK \
        (0xF << 0) /* Bits 3-0: VGP_EXT, VGP extension time */
#define PIXPAPER_PFS_VGP_EXT_0MS (0x0 << 0) /* 0000: 0 ms */
#define PIXPAPER_PFS_VGP_EXT_500MS (0x1 << 0) /* 0001: 500 ms */
#define PIXPAPER_PFS_VGP_EXT_1000MS (0x2 << 0) /* 0010: 1000 ms */
#define PIXPAPER_PFS_VGP_EXT_1500MS (0x3 << 0) /* 0011: 1500 ms */
#define PIXPAPER_PFS_VGP_EXT_2000MS (0x4 << 0) /* 0100: 2000 ms (default) */
#define PIXPAPER_PFS_VGP_EXT_2500MS (0x5 << 0) /* 0101: 2500 ms */
#define PIXPAPER_PFS_VGP_EXT_3000MS (0x6 << 0) /* 0110: 3000 ms */
#define PIXPAPER_PFS_VGP_EXT_3500MS (0x7 << 0) /* 0111: 3500 ms */
#define PIXPAPER_PFS_VGP_EXT_4000MS (0x8 << 0) /* 1000: 4000 ms */
#define PIXPAPER_PFS_VGP_EXT_4500MS (0x9 << 0) /* 1001: 4500 ms */
#define PIXPAPER_PFS_VGP_EXT_5000MS (0xA << 0) /* 1010: 5000 ms */
#define PIXPAPER_PFS_VGP_EXT_5500MS (0xB << 0) /* 1011: 5500 ms */
#define PIXPAPER_PFS_VGP_EXT_6000MS (0xC << 0) /* 1100: 6000 ms */
#define PIXPAPER_PFS_VGP_EXT_6500MS (0xD << 0) /* 1101: 6500 ms */
#define PIXPAPER_PFS_VGP_LEN_MASK \
        (0xF << 4) /* Bits 7-4: VGP_LEN, VGP at 10V during power-off */
#define PIXPAPER_PFS_VGP_LEN_0MS (0x0 << 4) /* 0000: 0 ms */
#define PIXPAPER_PFS_VGP_LEN_500MS (0x1 << 4) /* 0001: 500 ms */
#define PIXPAPER_PFS_VGP_LEN_1000MS (0x2 << 4) /* 0010: 1000 ms */
#define PIXPAPER_PFS_VGP_LEN_1500MS (0x3 << 4) /* 0011: 1500 ms */
#define PIXPAPER_PFS_VGP_LEN_2000MS (0x4 << 4) /* 0100: 2000 ms */
#define PIXPAPER_PFS_VGP_LEN_2500MS (0x5 << 4) /* 0101: 2500 ms (default) */
#define PIXPAPER_PFS_VGP_LEN_3000MS (0x6 << 4) /* 0110: 3000 ms */
#define PIXPAPER_PFS_VGP_LEN_3500MS (0x7 << 4) /* 0111: 3500 ms */
#define PIXPAPER_PFS_VGP_LEN_4000MS (0x8 << 4) /* 1000: 4000 ms */
#define PIXPAPER_PFS_VGP_LEN_4500MS (0x9 << 4) /* 1001: 4500 ms */
#define PIXPAPER_PFS_VGP_LEN_5000MS (0xA << 4) /* 1010: 5000 ms */
#define PIXPAPER_PFS_VGP_LEN_5500MS (0xB << 4) /* 1011: 5500 ms */
#define PIXPAPER_PFS_VGP_LEN_6000MS (0xC << 4) /* 1100: 6000 ms */
#define PIXPAPER_PFS_VGP_LEN_6500MS (0xD << 4) /* 1101: 6500 ms */
#define PIXPAPER_PFS_CONFIG2           \
        (PIXPAPER_PFS_VGP_EXT_1000MS | \
         PIXPAPER_PFS_VGP_LEN_2500MS) /* 0x54: VGP extension 1000 ms, VGP at 10V for 2500 ms */

/* Third Parameter */
#define PIXPAPER_PFS_XON_LEN_MASK \
        (0xF << 0) /* Bits 3-0: XON_LEN, XON enable time */
#define PIXPAPER_PFS_XON_LEN_0MS (0x0 << 0) /* 0000: 0 ms */
#define PIXPAPER_PFS_XON_LEN_500MS (0x1 << 0) /* 0001: 500 ms */
#define PIXPAPER_PFS_XON_LEN_1000MS (0x2 << 0) /* 0010: 1000 ms */
#define PIXPAPER_PFS_XON_LEN_1500MS (0x3 << 0) /* 0011: 1500 ms */
#define PIXPAPER_PFS_XON_LEN_2000MS (0x4 << 0) /* 0100: 2000 ms (default) */
#define PIXPAPER_PFS_XON_LEN_2500MS (0x5 << 0) /* 0101: 2500 ms */
#define PIXPAPER_PFS_XON_LEN_3000MS (0x6 << 0) /* 0110: 3000 ms */
#define PIXPAPER_PFS_XON_LEN_3500MS (0x7 << 0) /* 0111: 3500 ms */
#define PIXPAPER_PFS_XON_LEN_4000MS (0x8 << 0) /* 1000: 4000 ms */
#define PIXPAPER_PFS_XON_LEN_4500MS (0x9 << 0) /* 1001: 4500 ms */
#define PIXPAPER_PFS_XON_LEN_5000MS (0xA << 0) /* 1010: 5000 ms */
#define PIXPAPER_PFS_XON_LEN_5500MS (0xB << 0) /* 1011: 5500 ms */
#define PIXPAPER_PFS_XON_LEN_6000MS (0xC << 0) /* 1100: 6000 ms */
#define PIXPAPER_PFS_XON_DLY_MASK \
        (0xF << 4) /* Bits 7-4: XON_DLY, XON delay time */
#define PIXPAPER_PFS_XON_DLY_0MS (0x0 << 4) /* 0000: 0 ms */
#define PIXPAPER_PFS_XON_DLY_500MS (0x1 << 4) /* 0001: 500 ms */
#define PIXPAPER_PFS_XON_DLY_1000MS (0x2 << 4) /* 0010: 1000 ms */
#define PIXPAPER_PFS_XON_DLY_1500MS (0x3 << 4) /* 0011: 1500 ms */
#define PIXPAPER_PFS_XON_DLY_2000MS (0x4 << 4) /* 0100: 2000 ms (default) */
#define PIXPAPER_PFS_XON_DLY_2500MS (0x5 << 4) /* 0101: 2500 ms */
#define PIXPAPER_PFS_XON_DLY_3000MS (0x6 << 4) /* 0110: 3000 ms */
#define PIXPAPER_PFS_XON_DLY_3500MS (0x7 << 4) /* 0111: 3500 ms */
#define PIXPAPER_PFS_XON_DLY_4000MS (0x8 << 4) /* 1000: 4000 ms */
#define PIXPAPER_PFS_XON_DLY_4500MS (0x9 << 4) /* 1001: 4500 ms */
#define PIXPAPER_PFS_XON_DLY_5000MS (0xA << 4) /* 1010: 5000 ms */
#define PIXPAPER_PFS_XON_DLY_5500MS (0xB << 4) /* 1011: 5500 ms */
#define PIXPAPER_PFS_XON_DLY_6000MS (0xC << 4) /* 1100: 6000 ms */
#define PIXPAPER_PFS_CONFIG3           \
        (PIXPAPER_PFS_XON_LEN_2000MS | \
         PIXPAPER_PFS_XON_DLY_2000MS) /* 0x44: XON enable and delay at 2000 ms */

/* R06H BTST - Booster Soft Start Command */
/* First Parameter */
#define PIXPAPER_BTST_PHA_SFT_MASK \
        (3 << 0) /* Bits 1-0: PHA_SFT, soft start period for phase A */
#define PIXPAPER_BTST_PHA_SFT_10MS (0x0 << 0) /* 00: 10 ms (default) */
#define PIXPAPER_BTST_PHA_SFT_20MS (0x1 << 0) /* 01: 20 ms */
#define PIXPAPER_BTST_PHA_SFT_30MS (0x2 << 0) /* 10: 30 ms */
#define PIXPAPER_BTST_PHA_SFT_40MS (0x3 << 0) /* 11: 40 ms */
#define PIXPAPER_BTST_PHB_SFT_MASK \
        (3 << 2) /* Bits 3-2: PHB_SFT, soft start period for phase B */
#define PIXPAPER_BTST_PHB_SFT_10MS (0x0 << 2) /* 00: 10 ms (default) */
#define PIXPAPER_BTST_PHB_SFT_20MS (0x1 << 2) /* 01: 20 ms */
#define PIXPAPER_BTST_PHB_SFT_30MS (0x2 << 2) /* 10: 30 ms */
#define PIXPAPER_BTST_PHB_SFT_40MS (0x3 << 2) /* 11: 40 ms */
#define PIXPAPER_BTST_CONFIG1         \
        (PIXPAPER_BTST_PHA_SFT_40MS | \
         PIXPAPER_BTST_PHB_SFT_40MS) /* 0x0F: 40 ms for phase A and B */

/* Second to Seventh Parameters (Driving Strength or Minimum OFF Time) */
#define PIXPAPER_BTST_CONFIG2 0x0A /* Strength11 */
#define PIXPAPER_BTST_CONFIG3 0x2F /* Period48 */
#define PIXPAPER_BTST_CONFIG4 0x25 /* Strength38 */
#define PIXPAPER_BTST_CONFIG5 0x22 /* Period35 */
#define PIXPAPER_BTST_CONFIG6 0x2E /* Strength47 */
#define PIXPAPER_BTST_CONFIG7 0x21 /* Period34 */

/* R12H: DRF (Display Refresh) */
#define PIXPAPER_DRF_VCOM_AC 0x00 /* AC VCOM: VCOM follows LUTC (default) */
#define PIXPAPER_DRF_VCOM_DC 0x01 /* DC VCOM: VCOM fixed to VCOMDC */

/* R30H PLL - PLL Control Register */
/* First Parameter */
#define PIXPAPER_PLL_FR_MASK (0x7 << 0) /* Bits 2-0: FR, frame rate */
#define PIXPAPER_PLL_FR_12_5HZ (0x0 << 0) /* 000: 12.5 Hz */
#define PIXPAPER_PLL_FR_25HZ (0x1 << 0) /* 001: 25 Hz */
#define PIXPAPER_PLL_FR_50HZ (0x2 << 0) /* 010: 50 Hz (default) */
#define PIXPAPER_PLL_FR_65HZ (0x3 << 0) /* 011: 65 Hz */
#define PIXPAPER_PLL_FR_75HZ (0x4 << 0) /* 100: 75 Hz */
#define PIXPAPER_PLL_FR_85HZ (0x5 << 0) /* 101: 85 Hz */
#define PIXPAPER_PLL_FR_100HZ (0x6 << 0) /* 110: 100 Hz */
#define PIXPAPER_PLL_FR_120HZ (0x7 << 0) /* 111: 120 Hz */
#define PIXPAPER_PLL_DFR \
        (1 << 3) /* Bit 3: Dynamic frame rate, 0=disabled (default), 1=enabled */
#define PIXPAPER_PLL_CONFIG \
        (PIXPAPER_PLL_FR_50HZ) /* 0x02: 50 Hz, dynamic frame rate disabled */

/* R41H TSE - Temperature Sensor Calibration Register */
/* First Parameter */
#define PIXPAPER_TSE_TO_MASK \
        (0xF << 0) /* Bits 3-0: TO[3:0], temperature offset */
#define PIXPAPER_TSE_TO_POS_0C (0x0 << 0) /* 0000: +0°C (default) */
#define PIXPAPER_TSE_TO_POS_0_5C (0x1 << 0) /* 0001: +0.5°C */
#define PIXPAPER_TSE_TO_POS_1C (0x2 << 0) /* 0010: +1°C */
#define PIXPAPER_TSE_TO_POS_1_5C (0x3 << 0) /* 0011: +1.5°C */
#define PIXPAPER_TSE_TO_POS_2C (0x4 << 0) /* 0100: +2°C */
#define PIXPAPER_TSE_TO_POS_2_5C (0x5 << 0) /* 0101: +2.5°C */
#define PIXPAPER_TSE_TO_POS_3C (0x6 << 0) /* 0110: +3°C */
#define PIXPAPER_TSE_TO_POS_3_5C (0x7 << 0) /* 0111: +3.5°C */
#define PIXPAPER_TSE_TO_NEG_4C (0x8 << 0) /* 1000: -4°C */
#define PIXPAPER_TSE_TO_NEG_3_5C (0x9 << 0) /* 1001: -3.5°C */
#define PIXPAPER_TSE_TO_NEG_3C (0xA << 0) /* 1010: -3°C */
#define PIXPAPER_TSE_TO_NEG_2_5C (0xB << 0) /* 1011: -2.5°C */
#define PIXPAPER_TSE_TO_NEG_2C (0xC << 0) /* 1100: -2°C */
#define PIXPAPER_TSE_TO_NEG_1_5C (0xD << 0) /* 1101: -1.5°C */
#define PIXPAPER_TSE_TO_NEG_1C (0xE << 0) /* 1110: -1°C */
#define PIXPAPER_TSE_TO_NEG_0_5C (0xF << 0) /* 1111: -0.5°C */
#define PIXPAPER_TSE_TO_FINE_MASK \
        (0x3 << 4) /* Bits 5-4: TO[5:4], fine adjustment for positive offsets */
#define PIXPAPER_TSE_TO_FINE_0C (0x0 << 4) /* 00: +0.0°C (default) */
#define PIXPAPER_TSE_TO_FINE_0_25C (0x1 << 4) /* 01: +0.25°C */
#define PIXPAPER_TSE_ENABLE \
        (0 << 7) /* Bit 7: TSE, 0=internal sensor enabled (default), 1=disabled (external) */
#define PIXPAPER_TSE_DISABLE \
        (1 << 7) /* Bit 7: TSE, 1=internal sensor disabled, use external */
#define PIXPAPER_TSE_CONFIG                                 \
        (PIXPAPER_TSE_TO_POS_0C | PIXPAPER_TSE_TO_FINE_0C | \
         PIXPAPER_TSE_ENABLE) /* 0x00: Internal sensor enabled, +0°C offset */

/* R4DH */
#define PIXPAPER_UNKNOWN_4D_CONFIG \
        0x78 /* This value is essential for initialization, derived from userspace examples. */

/* R50H CDI - VCOM and DATA Interval Setting Register */
/* First Parameter */
#define PIXPAPER_CDI_INTERVAL_MASK \
        (0xF << 0) /* Bits 3-0: CDI[3:0], VCOM and data interval (hsync) */
#define PIXPAPER_CDI_17_HSYNC (0x0 << 0) /* 0000: 17 hsync */
#define PIXPAPER_CDI_16_HSYNC (0x1 << 0) /* 0001: 16 hsync */
#define PIXPAPER_CDI_15_HSYNC (0x2 << 0) /* 0010: 15 hsync */
#define PIXPAPER_CDI_14_HSYNC (0x3 << 0) /* 0011: 14 hsync */
#define PIXPAPER_CDI_13_HSYNC (0x4 << 0) /* 0100: 13 hsync */
#define PIXPAPER_CDI_12_HSYNC (0x5 << 0) /* 0101: 12 hsync */
#define PIXPAPER_CDI_11_HSYNC (0x6 << 0) /* 0110: 11 hsync */
#define PIXPAPER_CDI_10_HSYNC (0x7 << 0) /* 0111: 10 hsync (default) */
#define PIXPAPER_CDI_9_HSYNC (0x8 << 0) /* 1000: 9 hsync */
#define PIXPAPER_CDI_8_HSYNC (0x9 << 0) /* 1001: 8 hsync */
#define PIXPAPER_CDI_7_HSYNC (0xA << 0) /* 1010: 7 hsync */
#define PIXPAPER_CDI_6_HSYNC (0xB << 0) /* 1011: 6 hsync */
#define PIXPAPER_CDI_5_HSYNC (0xC << 0) /* 1100: 5 hsync */
#define PIXPAPER_CDI_4_HSYNC (0xD << 0) /* 1101: 4 hsync */
#define PIXPAPER_CDI_3_HSYNC (0xE << 0) /* 1110: 3 hsync */
#define PIXPAPER_CDI_2_HSYNC (0xF << 0) /* 1111: 2 hsync */
#define PIXPAPER_CDI_DDX \
        (1 << 4) /* Bit 4: DDX, 0=grayscale mapping 0, 1=grayscale mapping 1 (default) */
#define PIXPAPER_CDI_VBD_MASK \
        (0x7 << 5) /* Bits 7-5: VBD[2:0], border data selection */
#define PIXPAPER_CDI_VBD_FLOAT (0x0 << 5) /* 000: Floating (DDX=0 or 1) */
#define PIXPAPER_CDI_VBD_GRAY3_DDX0 \
        (0x1 << 5) /* 001: Gray3 (border_buf=011) when DDX=0 */
#define PIXPAPER_CDI_VBD_GRAY2_DDX0 \
        (0x2 << 5) /* 010: Gray2 (border_buf=010) when DDX=0 */
#define PIXPAPER_CDI_VBD_GRAY1_DDX0 \
        (0x3 << 5) /* 011: Gray1 (border_buf=001) when DDX=0 */
#define PIXPAPER_CDI_VBD_GRAY0_DDX0 \
        (0x4 << 5) /* 100: Gray0 (border_buf=000) when DDX=0 */
#define PIXPAPER_CDI_VBD_GRAY0_DDX1 \
        (0x0 << 5) /* 000: Gray0 (border_buf=000) when DDX=1 */
#define PIXPAPER_CDI_VBD_GRAY1_DDX1 \
        (0x1 << 5) /* 001: Gray1 (border_buf=001) when DDX=1 */
#define PIXPAPER_CDI_VBD_GRAY2_DDX1 \
        (0x2 << 5) /* 010: Gray2 (border_buf=010) when DDX=1 */
#define PIXPAPER_CDI_VBD_GRAY3_DDX1 \
        (0x3 << 5) /* 011: Gray3 (border_buf=011) when DDX=1 */
#define PIXPAPER_CDI_VBD_FLOAT_DDX1 (0x4 << 5) /* 100: Floating when DDX=1 */
#define PIXPAPER_CDI_CONFIG                         \
        (PIXPAPER_CDI_10_HSYNC | PIXPAPER_CDI_DDX | \
         PIXPAPER_CDI_VBD_GRAY1_DDX1) /* 0x37: 10 hsync, DDX=1, border Gray1 */

/* R60H */
#define PIXPAPER_UNKNOWN_60_CONFIG1 \
        0x02 /* This value is essential for initialization, derived from userspace examples. */
#define PIXPAPER_UNKNOWN_60_CONFIG2 \
        0x02 /* This value is essential for initialization, derived from userspace examples. */

/* R61H TRES - Resolution Setting Register */
#define PIXPAPER_TRES_HRES_H                  \
        ((PIXPAPER_PANEL_BUFFER_WIDTH >> 8) & \
         0xFF) /* HRES[9:8]: High byte of horizontal resolution (128) */
#define PIXPAPER_TRES_HRES_L           \
        (PIXPAPER_PANEL_BUFFER_WIDTH & \
         0xFF) /* HRES[7:0]: Low byte of horizontal resolution (128 = 0x80) */
#define PIXPAPER_TRES_VRES_H      \
        ((PIXPAPER_HEIGHT >> 8) & \
         0xFF) /* VRES[9:8]: High byte of vertical resolution (250) */
#define PIXPAPER_TRES_VRES_L \
        (PIXPAPER_HEIGHT &   \
         0xFF) /* VRES[7:0]: Low byte of vertical resolution (250 = 0xFA) */

/* R65H GSST - Gate/Source Start Setting Register */
#define PIXPAPER_GSST_S_START 0x00 /* S_Start[7:0]: First source line (S0) */
#define PIXPAPER_GSST_RESERVED 0x00 /* Reserved byte */
#define PIXPAPER_GSST_G_START_H \
        0x00 /* G_Start[8]: High bit of first gate line (G0) */
#define PIXPAPER_GSST_G_START_L \
        0x00 /* G_Start[7:0]: Low byte of first gate line (G0) */

/* RB4H */
#define PIXPAPER_UNKNOWN_B4_CONFIG \
        0xD0 /* This value is essential for initialization, derived from userspace examples. */

/* RB5H */
#define PIXPAPER_UNKNOWN_B5_CONFIG \
        0x03 /* This value is essential for initialization, derived from userspace examples. */

/* RE0H */
#define PIXPAPER_UNKNOWN_E0_CONFIG \
        0x00 /* This value is essential for initialization, derived from userspace examples. */

/* RE3H PWS - Power Saving Register */
/* First Parameter */
#define PIXPAPER_PWS_VCOM_W_MASK \
        (0xF                     \
         << 4) /* Bits 7-4: VCOM_W[3:0], VCOM power-saving width (line periods) */
#define PIXPAPER_PWS_VCOM_W_0 (0x0 << 4) /* 0000: 0 line periods */
#define PIXPAPER_PWS_VCOM_W_1 (0x1 << 4) /* 0001: 1 line period */
#define PIXPAPER_PWS_VCOM_W_2 (0x2 << 4) /* 0010: 2 line periods */
#define PIXPAPER_PWS_VCOM_W_3 (0x3 << 4) /* 0011: 3 line periods */
#define PIXPAPER_PWS_VCOM_W_4 (0x4 << 4) /* 0100: 4 line periods */
#define PIXPAPER_PWS_VCOM_W_5 (0x5 << 4) /* 0101: 5 line periods */
#define PIXPAPER_PWS_VCOM_W_6 (0x6 << 4) /* 0110: 6 line periods */
#define PIXPAPER_PWS_VCOM_W_7 (0x7 << 4) /* 0111: 7 line periods */
#define PIXPAPER_PWS_VCOM_W_8 (0x8 << 4) /* 1000: 8 line periods */
#define PIXPAPER_PWS_VCOM_W_9 (0x9 << 4) /* 1001: 9 line periods */
#define PIXPAPER_PWS_VCOM_W_10 (0xA << 4) /* 1010: 10 line periods */
#define PIXPAPER_PWS_VCOM_W_11 (0xB << 4) /* 1011: 11 line periods */
#define PIXPAPER_PWS_VCOM_W_12 (0xC << 4) /* 1100: 12 line periods */
#define PIXPAPER_PWS_VCOM_W_13 (0xD << 4) /* 1101: 13 line periods */
#define PIXPAPER_PWS_VCOM_W_14 (0xE << 4) /* 1110: 14 line periods */
#define PIXPAPER_PWS_VCOM_W_15 (0xF << 4) /* 1111: 15 line periods */
#define PIXPAPER_PWS_SD_W_MASK \
        (0xF << 0) /* Bits 3-0: SD_W[3:0], source power-saving width (660 ns units) */
#define PIXPAPER_PWS_SD_W_0 (0x0 << 0) /* 0000: 0 ns */
#define PIXPAPER_PWS_SD_W_1 (0x1 << 0) /* 0001: 660 ns */
#define PIXPAPER_PWS_SD_W_2 (0x2 << 0) /* 0010: 1320 ns */
#define PIXPAPER_PWS_SD_W_3 (0x3 << 0) /* 0011: 1980 ns */
#define PIXPAPER_PWS_SD_W_4 (0x4 << 0) /* 0100: 2640 ns */
#define PIXPAPER_PWS_SD_W_5 (0x5 << 0) /* 0101: 3300 ns */
#define PIXPAPER_PWS_SD_W_6 (0x6 << 0) /* 0110: 3960 ns */
#define PIXPAPER_PWS_SD_W_7 (0x7 << 0) /* 0111: 4620 ns */
#define PIXPAPER_PWS_SD_W_8 (0x8 << 0) /* 1000: 5280 ns */
#define PIXPAPER_PWS_SD_W_9 (0x9 << 0) /* 1001: 5940 ns */
#define PIXPAPER_PWS_SD_W_10 (0xA << 0) /* 1010: 6600 ns */
#define PIXPAPER_PWS_SD_W_11 (0xB << 0) /* 1011: 7260 ns */
#define PIXPAPER_PWS_SD_W_12 (0xC << 0) /* 1100: 7920 ns */
#define PIXPAPER_PWS_SD_W_13 (0xD << 0) /* 1101: 8580 ns */
#define PIXPAPER_PWS_SD_W_14 (0xE << 0) /* 1110: 9240 ns */
#define PIXPAPER_PWS_SD_W_15 (0xF << 0) /* 1111: 9900 ns */
#define PIXPAPER_PWS_CONFIG      \
        (PIXPAPER_PWS_VCOM_W_2 | \
         PIXPAPER_PWS_SD_W_2) /* 0x22: VCOM 2 line periods (160 µs), source 1320 ns */

/* RE7H */
#define PIXPAPER_UNKNOWN_E7_CONFIG \
        0x1C /* This value is essential for initialization, derived from userspace examples. */

/* RE9H */
#define PIXPAPER_UNKNOWN_E9_CONFIG \
        0x01 /* This value is essential for initialization, derived from userspace examples. */

MODULE_IMPORT_NS("DMA_BUF");

/*
 * The panel has a visible resolution of 122x250.
 * However, the controller requires the horizontal resolution to be aligned to 128 pixels.
 * No porch or sync timing values are provided in the datasheet, so we define minimal
 * placeholder values to satisfy the DRM framework.
 */

/* Panel visible resolution */
#define PIXPAPER_WIDTH           122
#define PIXPAPER_HEIGHT          250

/* Controller requires 128 horizontal pixels total (for memory alignment) */
#define PIXPAPER_HTOTAL          128
#define PIXPAPER_HFP             2
#define PIXPAPER_HSYNC           2
#define PIXPAPER_HBP             (PIXPAPER_HTOTAL - PIXPAPER_WIDTH - PIXPAPER_HFP - PIXPAPER_HSYNC)

/*
 * According to the datasheet, the total vertical blanking must be 55 lines,
 * regardless of how the vertical back porch is set.
 * Here we allocate VFP=2, VSYNC=2, and VBP=51 to sum up to 55 lines.
 * Total vertical lines = 250 (visible) + 55 (blanking) = 305.
 */
#define PIXPAPER_VTOTAL  (250 + 55)
#define PIXPAPER_VFP     2
#define PIXPAPER_VSYNC   2
#define PIXPAPER_VBP     (55 - PIXPAPER_VFP - PIXPAPER_VSYNC)

/*
 * Pixel clock calculation:
 * pixel_clock = htotal * vtotal * refresh_rate
 *             = 128 * 305 * 50
 *             = 1,952,000 Hz = 1952 kHz
 */
#define PIXPAPER_PIXEL_CLOCK     1952

#define PIXPAPER_WIDTH_MM        24    /* approximate from 23.7046mm */
#define PIXPAPER_HEIGHT_MM       49    /* approximate from 48.55mm */

#define PIXPAPER_SPI_BITS_PER_WORD      8
#define PIXPAPER_SPI_SPEED_DEFAULT      1000000

#define PIXPAPER_PANEL_BUFFER_WIDTH     128
#define PIXPAPER_PANEL_BUFFER_TWO_BYTES_PER_ROW (PIXPAPER_PANEL_BUFFER_WIDTH / 4)

#define PIXPAPER_COLOR_THRESHOLD_LOW_CHANNEL            60
#define PIXPAPER_COLOR_THRESHOLD_HIGH_CHANNEL           200
#define PIXPAPER_COLOR_THRESHOLD_YELLOW_MIN_GREEN       180

struct pixpaper_error_ctx {
        int errno_code;
};

struct pixpaper_panel {
        struct drm_device drm;
        struct drm_plane plane;
        struct drm_crtc crtc;
        struct drm_encoder encoder;
        struct drm_connector connector;

        struct spi_device *spi;
        struct gpio_desc *reset;
        struct gpio_desc *busy;
        struct gpio_desc *dc;
};

static inline struct pixpaper_panel *to_pixpaper_panel(struct drm_device *drm)
{
        return container_of(drm, struct pixpaper_panel, drm);
}

static void pixpaper_wait_for_panel(struct pixpaper_panel *panel)
{
        unsigned int timeout_ms = 10000;
        unsigned long timeout_jiffies = jiffies + msecs_to_jiffies(timeout_ms);

        usleep_range(1000, 1500);
        while (gpiod_get_value_cansleep(panel->busy) != 1) {
                if (time_after(jiffies, timeout_jiffies)) {
                        drm_warn(&panel->drm, "Busy wait timed out\n");
                        return;
                }
                usleep_range(100, 200);
        }
}

static void pixpaper_spi_sync(struct spi_device *spi, struct spi_message *msg,
                              struct pixpaper_error_ctx *err)
{
        if (err->errno_code)
                return;

        int ret = spi_sync(spi, msg);

        if (ret < 0)
                err->errno_code = ret;
}

static void pixpaper_send_cmd(struct pixpaper_panel *panel, u8 cmd,
                              struct pixpaper_error_ctx *err)
{
        if (err->errno_code)
                return;

        struct spi_transfer xfer = {
                .tx_buf = &cmd,
                .len = 1,
        };
        struct spi_message msg;

        spi_message_init(&msg);
        spi_message_add_tail(&xfer, &msg);

        gpiod_set_value_cansleep(panel->dc, 0);
        usleep_range(1, 5);
        pixpaper_spi_sync(panel->spi, &msg, err);
}

static void pixpaper_send_data(struct pixpaper_panel *panel, u8 data,
                               struct pixpaper_error_ctx *err)
{
        if (err->errno_code)
                return;

        struct spi_transfer xfer = {
                .tx_buf = &data,
                .len = 1,
        };
        struct spi_message msg;

        spi_message_init(&msg);
        spi_message_add_tail(&xfer, &msg);

        gpiod_set_value_cansleep(panel->dc, 1);
        usleep_range(1, 5);
        pixpaper_spi_sync(panel->spi, &msg, err);
}

static int pixpaper_panel_hw_init(struct pixpaper_panel *panel)
{
        struct pixpaper_error_ctx err = { .errno_code = 0 };

        gpiod_set_value_cansleep(panel->reset, 0);
        msleep(50);
        gpiod_set_value_cansleep(panel->reset, 1);
        msleep(50);

        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_UNKNOWN_4D, &err);
        pixpaper_send_data(panel, PIXPAPER_UNKNOWN_4D_CONFIG, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_PANEL_SETTING, &err);
        pixpaper_send_data(panel, PIXPAPER_PSR_CONFIG, &err);
        pixpaper_send_data(panel, PIXPAPER_PSR_CONFIG2, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_POWER_SETTING, &err);
        pixpaper_send_data(panel, PIXPAPER_PWR_CONFIG1, &err);
        pixpaper_send_data(panel, PIXPAPER_PWR_CONFIG2, &err);
        pixpaper_send_data(panel, PIXPAPER_PWR_VSP_8_2V, &err);
        pixpaper_send_data(panel, PIXPAPER_PWR_VSPL_15V, &err);
        pixpaper_send_data(panel, PIXPAPER_PWR_VSN_4V, &err);
        pixpaper_send_data(panel, PIXPAPER_PWR_VSP_8_2V, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_POWER_OFF_SEQUENCE, &err);
        pixpaper_send_data(panel, PIXPAPER_PFS_CONFIG1, &err);
        pixpaper_send_data(panel, PIXPAPER_PFS_CONFIG2, &err);
        pixpaper_send_data(panel, PIXPAPER_PFS_CONFIG3, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_BOOSTER_SOFT_START, &err);
        pixpaper_send_data(panel, PIXPAPER_BTST_CONFIG1, &err);
        pixpaper_send_data(panel, PIXPAPER_BTST_CONFIG2, &err);
        pixpaper_send_data(panel, PIXPAPER_BTST_CONFIG3, &err);
        pixpaper_send_data(panel, PIXPAPER_BTST_CONFIG4, &err);
        pixpaper_send_data(panel, PIXPAPER_BTST_CONFIG5, &err);
        pixpaper_send_data(panel, PIXPAPER_BTST_CONFIG6, &err);
        pixpaper_send_data(panel, PIXPAPER_BTST_CONFIG7, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_PLL_CONTROL, &err);
        pixpaper_send_data(panel, PIXPAPER_PLL_CONFIG, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_TEMP_SENSOR_CALIB, &err);
        pixpaper_send_data(panel, PIXPAPER_TSE_CONFIG, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_VCOM_INTERVAL, &err);
        pixpaper_send_data(panel, PIXPAPER_CDI_CONFIG, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_UNKNOWN_60, &err);
        pixpaper_send_data(panel, PIXPAPER_UNKNOWN_60_CONFIG1, &err);
        pixpaper_send_data(panel, PIXPAPER_UNKNOWN_60_CONFIG2, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_RESOLUTION_SETTING, &err);
        pixpaper_send_data(panel, PIXPAPER_TRES_HRES_H, &err);
        pixpaper_send_data(panel, PIXPAPER_TRES_HRES_L, &err);
        pixpaper_send_data(panel, PIXPAPER_TRES_VRES_H, &err);
        pixpaper_send_data(panel, PIXPAPER_TRES_VRES_L, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_GATE_SOURCE_START, &err);
        pixpaper_send_data(panel, PIXPAPER_GSST_S_START, &err);
        pixpaper_send_data(panel, PIXPAPER_GSST_RESERVED, &err);
        pixpaper_send_data(panel, PIXPAPER_GSST_G_START_H, &err);
        pixpaper_send_data(panel, PIXPAPER_GSST_G_START_L, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_UNKNOWN_E7, &err);
        pixpaper_send_data(panel, PIXPAPER_UNKNOWN_E7_CONFIG, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_POWER_SAVING, &err);
        pixpaper_send_data(panel, PIXPAPER_PWS_CONFIG, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_UNKNOWN_E0, &err);
        pixpaper_send_data(panel, PIXPAPER_UNKNOWN_E0_CONFIG, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_UNKNOWN_B4, &err);
        pixpaper_send_data(panel, PIXPAPER_UNKNOWN_B4_CONFIG, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_UNKNOWN_B5, &err);
        pixpaper_send_data(panel, PIXPAPER_UNKNOWN_B5_CONFIG, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_UNKNOWN_E9, &err);
        pixpaper_send_data(panel, PIXPAPER_UNKNOWN_E9_CONFIG, &err);
        if (err.errno_code)
                goto init_fail;
        pixpaper_wait_for_panel(panel);

        return 0;

init_fail:
        drm_err(&panel->drm, "Hardware initialization failed (err=%d)\n",
                err.errno_code);
        return err.errno_code;
}

/*
 * Convert framebuffer pixels to 2-bit e-paper format:
 *   00 - White
 *   01 - Black
 *   10 - Yellow
 *   11 - Red
 */
static u8 pack_pixels_to_byte(__le32 *src_pixels, int i, int j,
                              struct drm_framebuffer *fb)
{
        u8 packed_byte = 0;
        int k;

        for (k = 0; k < 4; k++) {
                int current_pixel_x = j * 4 + k;
                u8 two_bit_val;

                if (current_pixel_x < PIXPAPER_WIDTH) {
                        u32 pixel_offset =
                                (i * (fb->pitches[0] / 4)) + current_pixel_x;
                        u32 pixel = le32_to_cpu(src_pixels[pixel_offset]);
                        u32 r = (pixel >> 16) & 0xFF;
                        u32 g = (pixel >> 8) & 0xFF;
                        u32 b = pixel & 0xFF;

                        if (r < PIXPAPER_COLOR_THRESHOLD_LOW_CHANNEL &&
                            g < PIXPAPER_COLOR_THRESHOLD_LOW_CHANNEL &&
                            b < PIXPAPER_COLOR_THRESHOLD_LOW_CHANNEL) {
                                two_bit_val = 0b00;
                        } else if (r > PIXPAPER_COLOR_THRESHOLD_HIGH_CHANNEL &&
                                   g > PIXPAPER_COLOR_THRESHOLD_HIGH_CHANNEL &&
                                   b > PIXPAPER_COLOR_THRESHOLD_HIGH_CHANNEL) {
                                two_bit_val = 0b01;
                        } else if (r > PIXPAPER_COLOR_THRESHOLD_HIGH_CHANNEL &&
                                   g < PIXPAPER_COLOR_THRESHOLD_LOW_CHANNEL &&
                                   b < PIXPAPER_COLOR_THRESHOLD_LOW_CHANNEL) {
                                two_bit_val = 0b11;
                        } else if (r > PIXPAPER_COLOR_THRESHOLD_HIGH_CHANNEL &&
                                   g > PIXPAPER_COLOR_THRESHOLD_YELLOW_MIN_GREEN &&
                                   b < PIXPAPER_COLOR_THRESHOLD_LOW_CHANNEL) {
                                two_bit_val = 0b10;
                        } else {
                                two_bit_val = 0b01;
                        }
                } else {
                        two_bit_val = 0b01;
                }

                packed_byte |= two_bit_val << ((3 - k) * 2);
        }

        return packed_byte;
}

static int pixpaper_plane_helper_atomic_check(struct drm_plane *plane,
                                              struct drm_atomic_state *state)
{
        struct drm_plane_state *new_plane_state =
                drm_atomic_get_new_plane_state(state, plane);
        struct drm_crtc *new_crtc = new_plane_state->crtc;
        struct drm_crtc_state *new_crtc_state = NULL;
        int ret;

        if (new_crtc)
                new_crtc_state = drm_atomic_get_new_crtc_state(state, new_crtc);

        ret = drm_atomic_helper_check_plane_state(new_plane_state,
                                                  new_crtc_state, DRM_PLANE_NO_SCALING,
                                                  DRM_PLANE_NO_SCALING, false, false);
        if (ret)
                return ret;
        else if (!new_plane_state->visible)
                return 0;

        return 0;
}

static int pixpaper_crtc_helper_atomic_check(struct drm_crtc *crtc,
                                             struct drm_atomic_state *state)
{
        struct drm_crtc_state *crtc_state =
                drm_atomic_get_new_crtc_state(state, crtc);

        if (!crtc_state->enable)
                return 0;

        return drm_atomic_helper_check_crtc_primary_plane(crtc_state);
}

static void pixpaper_crtc_atomic_enable(struct drm_crtc *crtc,
                                        struct drm_atomic_state *state)
{
        struct pixpaper_panel *panel = to_pixpaper_panel(crtc->dev);
        struct drm_device *drm = &panel->drm;
        int idx;
        struct pixpaper_error_ctx err = { .errno_code = 0 };

        if (!drm_dev_enter(drm, &idx))
                return;

        pixpaper_send_cmd(panel, PIXPAPER_CMD_POWER_ON, &err);
        if (err.errno_code) {
                drm_err_once(drm, "Failed to send PON command: %d\n", err.errno_code);
                goto exit_drm_dev;
        }

        pixpaper_wait_for_panel(panel);

        drm_dbg(drm, "Panel enabled and powered on\n");

exit_drm_dev:
        drm_dev_exit(idx);
}

static void pixpaper_crtc_atomic_disable(struct drm_crtc *crtc,
                                         struct drm_atomic_state *state)
{
        struct pixpaper_panel *panel = to_pixpaper_panel(crtc->dev);
        struct drm_device *drm = &panel->drm;
        struct pixpaper_error_ctx err = { .errno_code = 0 };
        int idx;

        if (!drm_dev_enter(drm, &idx))
                return;

        pixpaper_send_cmd(panel, PIXPAPER_CMD_POWER_OFF, &err);
        if (err.errno_code) {
                drm_err_once(drm, "Failed to send POF command: %d\n", err.errno_code);
                goto exit_drm_dev;
        }
        pixpaper_wait_for_panel(panel);

        drm_dbg(drm, "Panel disabled\n");

exit_drm_dev:
        drm_dev_exit(idx);
}

static void pixpaper_plane_atomic_update(struct drm_plane *plane,
                                         struct drm_atomic_state *state)
{
        struct drm_plane_state *plane_state =
                drm_atomic_get_new_plane_state(state, plane);
        struct drm_shadow_plane_state *shadow_plane_state =
                to_drm_shadow_plane_state(plane_state);
        struct drm_crtc *crtc = plane_state->crtc;
        struct pixpaper_panel *panel = to_pixpaper_panel(crtc->dev);

        struct drm_device *drm = &panel->drm;
        struct drm_framebuffer *fb = plane_state->fb;
        struct iosys_map map = shadow_plane_state->data[0];
        void *vaddr = map.vaddr;
        int i, j, idx;
        __le32 *src_pixels = NULL;
        struct pixpaper_error_ctx err = { .errno_code = 0 };

        if (!drm_dev_enter(drm, &idx))
                return;

        drm_dbg(drm, "Starting frame update (phys=%dx%d, buf_w=%d)\n",
                PIXPAPER_WIDTH, PIXPAPER_HEIGHT, PIXPAPER_PANEL_BUFFER_WIDTH);

        if (!fb || !plane_state->visible) {
                drm_err_once(drm, "No framebuffer or plane not visible, skipping update\n");
                goto update_cleanup;
        }

        src_pixels = (__le32 *)vaddr;

        pixpaper_send_cmd(panel, PIXPAPER_CMD_DATA_START_TRANSMISSION, &err);
        if (err.errno_code)
                goto update_cleanup;

        pixpaper_wait_for_panel(panel);

        for (i = 0; i < PIXPAPER_HEIGHT; i++) {
                for (j = 0; j < PIXPAPER_PANEL_BUFFER_TWO_BYTES_PER_ROW; j++) {
                        u8 packed_byte =
                                pack_pixels_to_byte(src_pixels, i, j, fb);

                        pixpaper_wait_for_panel(panel);
                        pixpaper_send_data(panel, packed_byte, &err);
                }
        }
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_POWER_ON, &err);
        if (err.errno_code) {
                drm_err_once(drm, "Failed to send PON command: %d\n", err.errno_code);
                goto update_cleanup;
        }
        pixpaper_wait_for_panel(panel);

        pixpaper_send_cmd(panel, PIXPAPER_CMD_DISPLAY_REFRESH, &err);
        pixpaper_send_data(panel, PIXPAPER_DRF_VCOM_AC, &err);
        if (err.errno_code) {
                drm_err_once(drm, "Failed sending data after DRF: %d\n", err.errno_code);
                goto update_cleanup;
        }
        pixpaper_wait_for_panel(panel);

update_cleanup:
        if (err.errno_code && err.errno_code != -ETIMEDOUT)
                drm_err_once(drm, "Frame update function failed with error %d\n", err.errno_code);

        drm_dev_exit(idx);
}

static const struct drm_display_mode pixpaper_mode = {
        .clock = PIXPAPER_PIXEL_CLOCK,
        .hdisplay = PIXPAPER_WIDTH,
        .hsync_start = PIXPAPER_WIDTH + PIXPAPER_HFP,
        .hsync_end = PIXPAPER_WIDTH + PIXPAPER_HFP + PIXPAPER_HSYNC,
        .htotal = PIXPAPER_HTOTAL,
        .vdisplay = PIXPAPER_HEIGHT,
        .vsync_start = PIXPAPER_HEIGHT + PIXPAPER_VFP,
        .vsync_end = PIXPAPER_HEIGHT + PIXPAPER_VFP + PIXPAPER_VSYNC,
        .vtotal = PIXPAPER_VTOTAL,
        .width_mm = PIXPAPER_WIDTH_MM,
        .height_mm = PIXPAPER_HEIGHT_MM,
        .type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED,
};

static int pixpaper_connector_get_modes(struct drm_connector *connector)
{
        return drm_connector_helper_get_modes_fixed(connector, &pixpaper_mode);
}

static const struct drm_plane_funcs pixpaper_plane_funcs = {
        .update_plane = drm_atomic_helper_update_plane,
        .disable_plane = drm_atomic_helper_disable_plane,
        .destroy = drm_plane_cleanup,
        DRM_GEM_SHADOW_PLANE_FUNCS,
};

static const struct drm_plane_helper_funcs pixpaper_plane_helper_funcs = {
        DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
        .atomic_check = pixpaper_plane_helper_atomic_check,
        .atomic_update = pixpaper_plane_atomic_update,
};

static const struct drm_crtc_funcs pixpaper_crtc_funcs = {
        .set_config = drm_atomic_helper_set_config,
        .page_flip = drm_atomic_helper_page_flip,
        .reset = drm_atomic_helper_crtc_reset,
        .destroy = drm_crtc_cleanup,
        .atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
        .atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
};

static enum drm_mode_status
pixpaper_mode_valid(struct drm_crtc *crtc, const struct drm_display_mode *mode)
{
        if (mode->hdisplay == PIXPAPER_WIDTH &&
            mode->vdisplay == PIXPAPER_HEIGHT) {
                return MODE_OK;
        }
        return MODE_BAD;
}

static const struct drm_crtc_helper_funcs pixpaper_crtc_helper_funcs = {
        .mode_valid = pixpaper_mode_valid,
        .atomic_check = pixpaper_crtc_helper_atomic_check,
        .atomic_enable = pixpaper_crtc_atomic_enable,
        .atomic_disable = pixpaper_crtc_atomic_disable,
};

static const struct drm_encoder_funcs pixpaper_encoder_funcs = {
        .destroy = drm_encoder_cleanup,
};

static const struct drm_connector_funcs pixpaper_connector_funcs = {
        .reset = drm_atomic_helper_connector_reset,
        .fill_modes = drm_helper_probe_single_connector_modes,
        .destroy = drm_connector_cleanup,
        .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
        .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
};

static const struct drm_connector_helper_funcs pixpaper_connector_helper_funcs = {
        .get_modes = pixpaper_connector_get_modes,
};

DEFINE_DRM_GEM_FOPS(pixpaper_fops);

static struct drm_driver pixpaper_drm_driver = {
        .driver_features = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,
        .fops = &pixpaper_fops,
        .name = "pixpaper",
        .desc = "DRM driver for PIXPAPER e-ink",
        .major = 1,
        .minor = 0,
        DRM_GEM_SHMEM_DRIVER_OPS,
        DRM_FBDEV_SHMEM_DRIVER_OPS,
};

static const struct drm_mode_config_funcs pixpaper_mode_config_funcs = {
        .fb_create = drm_gem_fb_create_with_dirty,
        .atomic_check = drm_atomic_helper_check,
        .atomic_commit = drm_atomic_helper_commit,
};

static int pixpaper_probe(struct spi_device *spi)
{
        struct device *dev = &spi->dev;
        struct pixpaper_panel *panel;
        struct drm_device *drm;
        int ret;

        panel = devm_drm_dev_alloc(dev, &pixpaper_drm_driver,
                                   struct pixpaper_panel, drm);
        if (IS_ERR(panel))
                return PTR_ERR(panel);

        drm = &panel->drm;
        panel->spi = spi;
        spi_set_drvdata(spi, panel);

        spi->mode = SPI_MODE_0;
        spi->bits_per_word = PIXPAPER_SPI_BITS_PER_WORD;

        if (!spi->max_speed_hz) {
                drm_warn(drm,
                         "spi-max-frequency not specified in DT, using default %u Hz\n",
                         PIXPAPER_SPI_SPEED_DEFAULT);
                spi->max_speed_hz = PIXPAPER_SPI_SPEED_DEFAULT;
        }

        ret = spi_setup(spi);
        if (ret < 0) {
                drm_err(drm, "SPI setup failed: %d\n", ret);
                return ret;
        }

        if (!dev->dma_mask)
                dev->dma_mask = &dev->coherent_dma_mask;
        ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));
        if (ret) {
                drm_err(drm, "Failed to set DMA mask: %d\n", ret);
                return ret;
        }

        panel->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
        if (IS_ERR(panel->reset))
                return PTR_ERR(panel->reset);

        panel->busy = devm_gpiod_get(dev, "busy", GPIOD_IN);
        if (IS_ERR(panel->busy))
                return PTR_ERR(panel->busy);

        panel->dc = devm_gpiod_get(dev, "dc", GPIOD_OUT_HIGH);
        if (IS_ERR(panel->dc))
                return PTR_ERR(panel->dc);

        ret = pixpaper_panel_hw_init(panel);
        if (ret) {
                drm_err(drm, "Panel hardware initialization failed: %d\n", ret);
                return ret;
        }

        ret = drmm_mode_config_init(drm);
        if (ret)
                return ret;
        drm->mode_config.funcs = &pixpaper_mode_config_funcs;
        drm->mode_config.min_width = PIXPAPER_WIDTH;
        drm->mode_config.max_width = PIXPAPER_WIDTH;
        drm->mode_config.min_height = PIXPAPER_HEIGHT;
        drm->mode_config.max_height = PIXPAPER_HEIGHT;

        ret = drm_universal_plane_init(drm, &panel->plane, 1,
                                       &pixpaper_plane_funcs,
                                       (const uint32_t[]){ DRM_FORMAT_XRGB8888 },
                                       1, NULL, DRM_PLANE_TYPE_PRIMARY, NULL);
        if (ret)
                return ret;
        drm_plane_helper_add(&panel->plane, &pixpaper_plane_helper_funcs);

        ret = drm_crtc_init_with_planes(drm, &panel->crtc, &panel->plane, NULL,
                                        &pixpaper_crtc_funcs, NULL);
        if (ret)
                return ret;
        drm_crtc_helper_add(&panel->crtc, &pixpaper_crtc_helper_funcs);

        ret = drm_encoder_init(drm, &panel->encoder, &pixpaper_encoder_funcs,
                               DRM_MODE_ENCODER_NONE, NULL);
        if (ret)
                return ret;
        panel->encoder.possible_crtcs = drm_crtc_mask(&panel->crtc);

        ret = drm_connector_init(drm, &panel->connector,
                                 &pixpaper_connector_funcs,
                                 DRM_MODE_CONNECTOR_SPI);
        if (ret)
                return ret;

        drm_connector_helper_add(&panel->connector,
                                 &pixpaper_connector_helper_funcs);
        drm_connector_attach_encoder(&panel->connector, &panel->encoder);

        drm_mode_config_reset(drm);

        ret = drm_dev_register(drm, 0);
        if (ret)
                return ret;

        drm_client_setup(drm, NULL);

        return 0;
}

static void pixpaper_remove(struct spi_device *spi)
{
        struct pixpaper_panel *panel = spi_get_drvdata(spi);

        if (!panel)
                return;

        drm_dev_unplug(&panel->drm);
        drm_atomic_helper_shutdown(&panel->drm);
}

static const struct spi_device_id pixpaper_ids[] = { { "pixpaper", 0 }, {} };
MODULE_DEVICE_TABLE(spi, pixpaper_ids);

static const struct of_device_id pixpaper_dt_ids[] = {
        { .compatible = "mayqueen,pixpaper" },
        {}
};
MODULE_DEVICE_TABLE(of, pixpaper_dt_ids);

static struct spi_driver pixpaper_spi_driver = {
        .driver = {
                .name = "pixpaper",
                .of_match_table = pixpaper_dt_ids,
        },
        .id_table = pixpaper_ids,
        .probe = pixpaper_probe,
        .remove = pixpaper_remove,
};

module_spi_driver(pixpaper_spi_driver);

MODULE_AUTHOR("LiangCheng Wang");
MODULE_DESCRIPTION("DRM SPI driver for PIXPAPER e-ink panel");
MODULE_LICENSE("GPL");