/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright(c) 2016, Analogix Semiconductor.
 *
 * Based on anx7808 driver obtained from chromeos with copyright:
 * Copyright(c) 2013, Google Inc.
 */

#include <linux/export.h>
#include <linux/regmap.h>

#include <drm/display/drm_dp_helper.h>
#include <drm/drm.h>
#include <drm/drm_print.h>

#include "analogix-i2c-dptx.h"

#define AUX_WAIT_TIMEOUT_MS     15
#define AUX_CH_BUFFER_SIZE      16

static int anx_i2c_dp_clear_bits(struct regmap *map, u8 reg, u8 mask)
{
        return regmap_update_bits(map, reg, mask, 0);
}

static bool anx_dp_aux_op_finished(struct regmap *map_dptx)
{
        unsigned int value;
        int err;

        err = regmap_read(map_dptx, SP_DP_AUX_CH_CTRL2_REG, &value);
        if (err < 0)
                return false;

        return (value & SP_AUX_EN) == 0;
}

static int anx_dp_aux_wait(struct regmap *map_dptx)
{
        unsigned long timeout;
        unsigned int status;
        int err;

        timeout = jiffies + msecs_to_jiffies(AUX_WAIT_TIMEOUT_MS) + 1;

        while (!anx_dp_aux_op_finished(map_dptx)) {
                if (time_after(jiffies, timeout)) {
                        if (!anx_dp_aux_op_finished(map_dptx)) {
                                DRM_ERROR("Timed out waiting AUX to finish\n");
                                return -ETIMEDOUT;
                        }

                        break;
                }

                usleep_range(1000, 2000);
        }

        /* Read the AUX channel access status */
        err = regmap_read(map_dptx, SP_AUX_CH_STATUS_REG, &status);
        if (err < 0) {
                DRM_ERROR("Failed to read from AUX channel: %d\n", err);
                return err;
        }

        if (status & SP_AUX_STATUS) {
                DRM_ERROR("Failed to wait for AUX channel (status: %02x)\n",
                          status);
                return -ETIMEDOUT;
        }

        return 0;
}

static int anx_dp_aux_address(struct regmap *map_dptx, unsigned int addr)
{
        int err;

        err = regmap_write(map_dptx, SP_AUX_ADDR_7_0_REG, addr & 0xff);
        if (err)
                return err;

        err = regmap_write(map_dptx, SP_AUX_ADDR_15_8_REG,
                           (addr & 0xff00) >> 8);
        if (err)
                return err;

        /*
         * DP AUX CH Address Register #2, only update bits[3:0]
         * [7:4] RESERVED
         * [3:0] AUX_ADDR[19:16], Register control AUX CH address.
         */
        err = regmap_update_bits(map_dptx, SP_AUX_ADDR_19_16_REG,
                                 SP_AUX_ADDR_19_16_MASK,
                                 (addr & 0xf0000) >> 16);

        if (err)
                return err;

        return 0;
}

ssize_t anx_dp_aux_transfer(struct regmap *map_dptx,
                                struct drm_dp_aux_msg *msg)
{
        u8 ctrl1 = msg->request;
        u8 ctrl2 = SP_AUX_EN;
        u8 *buffer = msg->buffer;
        int err;

        /* The DP AUX transmit and receive buffer has 16 bytes. */
        if (WARN_ON(msg->size > AUX_CH_BUFFER_SIZE))
                return -E2BIG;

        /* Zero-sized messages specify address-only transactions. */
        if (msg->size < 1)
                ctrl2 |= SP_ADDR_ONLY;
        else    /* For non-zero-sized set the length field. */
                ctrl1 |= (msg->size - 1) << SP_AUX_LENGTH_SHIFT;

        if ((msg->size > 0) && ((msg->request & DP_AUX_I2C_READ) == 0)) {
                /* When WRITE | MOT write values to data buffer */
                err = regmap_bulk_write(map_dptx,
                                        SP_DP_BUF_DATA0_REG, buffer,
                                        msg->size);
                if (err)
                        return err;
        }

        /* Write address and request */
        err = anx_dp_aux_address(map_dptx, msg->address);
        if (err)
                return err;

        err = regmap_write(map_dptx, SP_DP_AUX_CH_CTRL1_REG, ctrl1);
        if (err)
                return err;

        /* Start transaction */
        err = regmap_update_bits(map_dptx, SP_DP_AUX_CH_CTRL2_REG,
                                 SP_ADDR_ONLY | SP_AUX_EN, ctrl2);
        if (err)
                return err;

        err = anx_dp_aux_wait(map_dptx);
        if (err)
                return err;

        msg->reply = DP_AUX_I2C_REPLY_ACK;

        if ((msg->size > 0) && (msg->request & DP_AUX_I2C_READ)) {
                /* Read values from data buffer */
                err = regmap_bulk_read(map_dptx,
                                       SP_DP_BUF_DATA0_REG, buffer,
                                       msg->size);
                if (err)
                        return err;
        }

        err = anx_i2c_dp_clear_bits(map_dptx, SP_DP_AUX_CH_CTRL2_REG,
                                    SP_ADDR_ONLY);
        if (err)
                return err;

        return msg->size;
}
EXPORT_SYMBOL_GPL(anx_dp_aux_transfer);