// SPDX-License-Identifier: GPL-2.0-only
/*
 * Qualcomm External Bus Interface 2 (EBI2) driver
 * an older version of the Qualcomm Parallel Interface Controller (QPIC)
 *
 * Copyright (C) 2016 Linaro Ltd.
 *
 * Author: Linus Walleij <linus.walleij@linaro.org>
 *
 * See the device tree bindings for this block for more details on the
 * hardware.
 */

#include <linux/module.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/platform_device.h>
#include <linux/bitops.h>

/*
 * CS0, CS1, CS4 and CS5 are two bits wide, CS2 and CS3 are one bit.
 */
#define EBI2_CS0_ENABLE_MASK BIT(0)|BIT(1)
#define EBI2_CS1_ENABLE_MASK BIT(2)|BIT(3)
#define EBI2_CS2_ENABLE_MASK BIT(4)
#define EBI2_CS3_ENABLE_MASK BIT(5)
#define EBI2_CS4_ENABLE_MASK BIT(6)|BIT(7)
#define EBI2_CS5_ENABLE_MASK BIT(8)|BIT(9)
#define EBI2_CSN_MASK GENMASK(9, 0)

#define EBI2_XMEM_CFG 0x0000 /* Power management etc */

/*
 * SLOW CSn CFG
 *
 * Bits 31-28: RECOVERY recovery cycles (0 = 1, 1 = 2 etc) this is the time the
 *             memory continues to drive the data bus after OE is de-asserted.
 *             Inserted when reading one CS and switching to another CS or read
 *             followed by write on the same CS. Valid values 0 thru 15.
 * Bits 27-24: WR_HOLD write hold cycles, these are extra cycles inserted after
 *             every write minimum 1. The data out is driven from the time WE is
 *             asserted until CS is asserted. With a hold of 1, the CS stays
 *             active for 1 extra cycle etc. Valid values 0 thru 15.
 * Bits 23-16: WR_DELTA initial latency for write cycles inserted for the first
 *             write to a page or burst memory
 * Bits 15-8:  RD_DELTA initial latency for read cycles inserted for the first
 *             read to a page or burst memory
 * Bits 7-4:   WR_WAIT number of wait cycles for every write access, 0=1 cycle
 *             so 1 thru 16 cycles.
 * Bits 3-0:   RD_WAIT number of wait cycles for every read access, 0=1 cycle
 *             so 1 thru 16 cycles.
 */
#define EBI2_XMEM_CS0_SLOW_CFG 0x0008
#define EBI2_XMEM_CS1_SLOW_CFG 0x000C
#define EBI2_XMEM_CS2_SLOW_CFG 0x0010
#define EBI2_XMEM_CS3_SLOW_CFG 0x0014
#define EBI2_XMEM_CS4_SLOW_CFG 0x0018
#define EBI2_XMEM_CS5_SLOW_CFG 0x001C

#define EBI2_XMEM_RECOVERY_SHIFT        28
#define EBI2_XMEM_WR_HOLD_SHIFT         24
#define EBI2_XMEM_WR_DELTA_SHIFT        16
#define EBI2_XMEM_RD_DELTA_SHIFT        8
#define EBI2_XMEM_WR_WAIT_SHIFT         4
#define EBI2_XMEM_RD_WAIT_SHIFT         0

/*
 * FAST CSn CFG
 * Bits 31-28: ?
 * Bits 27-24: RD_HOLD: the length in cycles of the first segment of a read
 *             transfer. For a single read trandfer this will be the time
 *             from CS assertion to OE assertion.
 * Bits 18-24: ?
 * Bits 17-16: ADV_OE_RECOVERY, the number of cycles elapsed before an OE
 *             assertion, with respect to the cycle where ADV is asserted.
 *             2 means 2 cycles between ADV and OE. Values 0, 1, 2 or 3.
 * Bits 5:     ADDR_HOLD_ENA, The address is held for an extra cycle to meet
 *             hold time requirements with ADV assertion.
 *
 * The manual mentions "write precharge cycles" and "precharge cycles".
 * We have not been able to figure out which bit fields these correspond to
 * in the hardware, or what valid values exist. The current hypothesis is that
 * this is something just used on the FAST chip selects. There is also a "byte
 * device enable" flag somewhere for 8bit memories.
 */
#define EBI2_XMEM_CS0_FAST_CFG 0x0028
#define EBI2_XMEM_CS1_FAST_CFG 0x002C
#define EBI2_XMEM_CS2_FAST_CFG 0x0030
#define EBI2_XMEM_CS3_FAST_CFG 0x0034
#define EBI2_XMEM_CS4_FAST_CFG 0x0038
#define EBI2_XMEM_CS5_FAST_CFG 0x003C

#define EBI2_XMEM_RD_HOLD_SHIFT         24
#define EBI2_XMEM_ADV_OE_RECOVERY_SHIFT 16
#define EBI2_XMEM_ADDR_HOLD_ENA_SHIFT   5

/**
 * struct cs_data - struct with info on a chipselect setting
 * @enable_mask: mask to enable the chipselect in the EBI2 config
 * @slow_cfg: offset to XMEMC slow CS config
 * @fast_cfg: offset to XMEMC fast CS config
 */
struct cs_data {
        u32 enable_mask;
        u16 slow_cfg;
        u16 fast_cfg;
};

static const struct cs_data cs_info[] = {
        {
                /* CS0 */
                .enable_mask = EBI2_CS0_ENABLE_MASK,
                .slow_cfg = EBI2_XMEM_CS0_SLOW_CFG,
                .fast_cfg = EBI2_XMEM_CS0_FAST_CFG,
        },
        {
                /* CS1 */
                .enable_mask = EBI2_CS1_ENABLE_MASK,
                .slow_cfg = EBI2_XMEM_CS1_SLOW_CFG,
                .fast_cfg = EBI2_XMEM_CS1_FAST_CFG,
        },
        {
                /* CS2 */
                .enable_mask = EBI2_CS2_ENABLE_MASK,
                .slow_cfg = EBI2_XMEM_CS2_SLOW_CFG,
                .fast_cfg = EBI2_XMEM_CS2_FAST_CFG,
        },
        {
                /* CS3 */
                .enable_mask = EBI2_CS3_ENABLE_MASK,
                .slow_cfg = EBI2_XMEM_CS3_SLOW_CFG,
                .fast_cfg = EBI2_XMEM_CS3_FAST_CFG,
        },
        {
                /* CS4 */
                .enable_mask = EBI2_CS4_ENABLE_MASK,
                .slow_cfg = EBI2_XMEM_CS4_SLOW_CFG,
                .fast_cfg = EBI2_XMEM_CS4_FAST_CFG,
        },
        {
                /* CS5 */
                .enable_mask = EBI2_CS5_ENABLE_MASK,
                .slow_cfg = EBI2_XMEM_CS5_SLOW_CFG,
                .fast_cfg = EBI2_XMEM_CS5_FAST_CFG,
        },
};

/**
 * struct ebi2_xmem_prop - describes an XMEM config property
 * @prop: the device tree binding name
 * @max: maximum value for the property
 * @slowreg: true if this property is in the SLOW CS config register
 * else it is assumed to be in the FAST config register
 * @shift: the bit field start in the SLOW or FAST register for this
 * property
 */
struct ebi2_xmem_prop {
        const char *prop;
        u32 max;
        bool slowreg;
        u16 shift;
};

static const struct ebi2_xmem_prop xmem_props[] = {
        {
                .prop = "qcom,xmem-recovery-cycles",
                .max = 15,
                .slowreg = true,
                .shift = EBI2_XMEM_RECOVERY_SHIFT,
        },
        {
                .prop = "qcom,xmem-write-hold-cycles",
                .max = 15,
                .slowreg = true,
                .shift = EBI2_XMEM_WR_HOLD_SHIFT,
        },
        {
                .prop = "qcom,xmem-write-delta-cycles",
                .max = 255,
                .slowreg = true,
                .shift = EBI2_XMEM_WR_DELTA_SHIFT,
        },
        {
                .prop = "qcom,xmem-read-delta-cycles",
                .max = 255,
                .slowreg = true,
                .shift = EBI2_XMEM_RD_DELTA_SHIFT,
        },
        {
                .prop = "qcom,xmem-write-wait-cycles",
                .max = 15,
                .slowreg = true,
                .shift = EBI2_XMEM_WR_WAIT_SHIFT,
        },
        {
                .prop = "qcom,xmem-read-wait-cycles",
                .max = 15,
                .slowreg = true,
                .shift = EBI2_XMEM_RD_WAIT_SHIFT,
        },
        {
                .prop = "qcom,xmem-address-hold-enable",
                .max = 1, /* boolean prop */
                .slowreg = false,
                .shift = EBI2_XMEM_ADDR_HOLD_ENA_SHIFT,
        },
        {
                .prop = "qcom,xmem-adv-to-oe-recovery-cycles",
                .max = 3,
                .slowreg = false,
                .shift = EBI2_XMEM_ADV_OE_RECOVERY_SHIFT,
        },
        {
                .prop = "qcom,xmem-read-hold-cycles",
                .max = 15,
                .slowreg = false,
                .shift = EBI2_XMEM_RD_HOLD_SHIFT,
        },
};

static void qcom_ebi2_setup_chipselect(struct device_node *np,
                                       struct device *dev,
                                       void __iomem *ebi2_base,
                                       void __iomem *ebi2_xmem,
                                       u32 csindex)
{
        const struct cs_data *csd;
        u32 slowcfg, fastcfg;
        u32 val;
        int ret;
        int i;

        csd = &cs_info[csindex];
        val = readl(ebi2_base);
        val |= csd->enable_mask;
        writel(val, ebi2_base);
        dev_dbg(dev, "enabled CS%u\n", csindex);

        /* Next set up the XMEMC */
        slowcfg = 0;
        fastcfg = 0;

        for (i = 0; i < ARRAY_SIZE(xmem_props); i++) {
                const struct ebi2_xmem_prop *xp = &xmem_props[i];

                /* All are regular u32 values */
                ret = of_property_read_u32(np, xp->prop, &val);
                if (ret) {
                        dev_dbg(dev, "could not read %s for CS%d\n",
                                xp->prop, csindex);
                        continue;
                }

                /* First check boolean props */
                if (xp->max == 1 && val) {
                        if (xp->slowreg)
                                slowcfg |= BIT(xp->shift);
                        else
                                fastcfg |= BIT(xp->shift);
                        dev_dbg(dev, "set %s flag\n", xp->prop);
                        continue;
                }

                /* We're dealing with an u32 */
                if (val > xp->max) {
                        dev_err(dev,
                                "too high value for %s: %u, capped at %u\n",
                                xp->prop, val, xp->max);
                        val = xp->max;
                }
                if (xp->slowreg)
                        slowcfg |= (val << xp->shift);
                else
                        fastcfg |= (val << xp->shift);
                dev_dbg(dev, "set %s to %u\n", xp->prop, val);
        }

        dev_info(dev, "CS%u: SLOW CFG 0x%08x, FAST CFG 0x%08x\n",
                 csindex, slowcfg, fastcfg);

        if (slowcfg)
                writel(slowcfg, ebi2_xmem + csd->slow_cfg);
        if (fastcfg)
                writel(fastcfg, ebi2_xmem + csd->fast_cfg);
}

static int qcom_ebi2_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct device *dev = &pdev->dev;
        struct resource *res;
        void __iomem *ebi2_base;
        void __iomem *ebi2_xmem;
        struct clk *ebi2xclk;
        struct clk *ebi2clk;
        bool have_children = false;
        u32 val;
        int ret;

        ebi2xclk = devm_clk_get(dev, "ebi2x");
        if (IS_ERR(ebi2xclk))
                return PTR_ERR(ebi2xclk);

        ret = clk_prepare_enable(ebi2xclk);
        if (ret) {
                dev_err(dev, "could not enable EBI2X clk (%d)\n", ret);
                return ret;
        }

        ebi2clk = devm_clk_get(dev, "ebi2");
        if (IS_ERR(ebi2clk)) {
                ret = PTR_ERR(ebi2clk);
                goto err_disable_2x_clk;
        }

        ret = clk_prepare_enable(ebi2clk);
        if (ret) {
                dev_err(dev, "could not enable EBI2 clk\n");
                goto err_disable_2x_clk;
        }

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        ebi2_base = devm_ioremap_resource(dev, res);
        if (IS_ERR(ebi2_base)) {
                ret = PTR_ERR(ebi2_base);
                goto err_disable_clk;
        }

        res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
        ebi2_xmem = devm_ioremap_resource(dev, res);
        if (IS_ERR(ebi2_xmem)) {
                ret = PTR_ERR(ebi2_xmem);
                goto err_disable_clk;
        }

        /* Allegedly this turns the power save mode off */
        writel(0UL, ebi2_xmem + EBI2_XMEM_CFG);

        /* Disable all chipselects */
        val = readl(ebi2_base);
        val &= ~EBI2_CSN_MASK;
        writel(val, ebi2_base);

        /* Walk over the child nodes and see what chipselects we use */
        for_each_available_child_of_node_scoped(np, child) {
                u32 csindex;

                /* Figure out the chipselect */
                ret = of_property_read_u32(child, "reg", &csindex);
                if (ret)
                        return ret;

                if (csindex > 5) {
                        dev_err(dev,
                                "invalid chipselect %u, we only support 0-5\n",
                                csindex);
                        continue;
                }

                qcom_ebi2_setup_chipselect(child,
                                           dev,
                                           ebi2_base,
                                           ebi2_xmem,
                                           csindex);

                /* We have at least one child */
                have_children = true;
        }

        if (have_children)
                return of_platform_default_populate(np, NULL, dev);
        return 0;

err_disable_clk:
        clk_disable_unprepare(ebi2clk);
err_disable_2x_clk:
        clk_disable_unprepare(ebi2xclk);

        return ret;
}

static const struct of_device_id qcom_ebi2_of_match[] = {
        { .compatible = "qcom,msm8660-ebi2", },
        { .compatible = "qcom,apq8060-ebi2", },
        { }
};

static struct platform_driver qcom_ebi2_driver = {
        .probe = qcom_ebi2_probe,
        .driver = {
                .name = "qcom-ebi2",
                .of_match_table = qcom_ebi2_of_match,
        },
};
module_platform_driver(qcom_ebi2_driver);
MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
MODULE_DESCRIPTION("Qualcomm EBI2 driver");