// SPDX-License-Identifier: GPL-2.0
/*
 * Apple SoC SPMI device driver
 *
 * Copyright The Asahi Linux Contributors
 *
 * Inspired by:
 *              OpenBSD support Copyright (c) 2021 Mark Kettenis <kettenis@openbsd.org>
 *              Correllium support Copyright (C) 2021 Corellium LLC
 *              hisi-spmi-controller.c
 *              spmi-pmic-arb.c Copyright (c) 2021, The Linux Foundation.
 */

#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/platform_device.h>
#include <linux/spmi.h>

/* SPMI Controller Registers */
#define SPMI_STATUS_REG 0
#define SPMI_CMD_REG 0x4
#define SPMI_RSP_REG 0x8

#define SPMI_RX_FIFO_EMPTY BIT(24)

#define REG_POLL_INTERVAL_US 10000
#define REG_POLL_TIMEOUT_US (REG_POLL_INTERVAL_US * 5)

struct apple_spmi {
        void __iomem *regs;
};

#define poll_reg(spmi, reg, val, cond) \
        readl_poll_timeout((spmi)->regs + (reg), (val), (cond), \
                           REG_POLL_INTERVAL_US, REG_POLL_TIMEOUT_US)

static inline u32 apple_spmi_pack_cmd(u8 opc, u8 sid, u16 saddr, size_t len)
{
        return opc | sid << 8 | saddr << 16 | (len - 1) | (1 << 15);
}

/* Wait for Rx FIFO to have something */
static int apple_spmi_wait_rx_not_empty(struct spmi_controller *ctrl)
{
        struct apple_spmi *spmi = spmi_controller_get_drvdata(ctrl);
        int ret;
        u32 status;

        ret = poll_reg(spmi, SPMI_STATUS_REG, status, !(status & SPMI_RX_FIFO_EMPTY));
        if (ret) {
                dev_err(&ctrl->dev,
                        "failed to wait for RX FIFO not empty\n");
                return ret;
        }

        return 0;
}

static int spmi_read_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
                         u16 saddr, u8 *buf, size_t len)
{
        struct apple_spmi *spmi = spmi_controller_get_drvdata(ctrl);
        u32 spmi_cmd = apple_spmi_pack_cmd(opc, sid, saddr, len);
        u32 rsp;
        size_t len_read = 0;
        u8 i;
        int ret;

        writel(spmi_cmd, spmi->regs + SPMI_CMD_REG);

        ret = apple_spmi_wait_rx_not_empty(ctrl);
        if (ret)
                return ret;

        /* Discard SPMI reply status */
        readl(spmi->regs + SPMI_RSP_REG);

        /* Read SPMI data reply */
        while (len_read < len) {
                rsp = readl(spmi->regs + SPMI_RSP_REG);
                i = 0;
                while ((len_read < len) && (i < 4)) {
                        buf[len_read++] = ((0xff << (8 * i)) & rsp) >> (8 * i);
                        i += 1;
                }
        }

        return 0;
}

static int spmi_write_cmd(struct spmi_controller *ctrl, u8 opc, u8 sid,
                          u16 saddr, const u8 *buf, size_t len)
{
        struct apple_spmi *spmi = spmi_controller_get_drvdata(ctrl);
        u32 spmi_cmd = apple_spmi_pack_cmd(opc, sid, saddr, len);
        size_t i = 0, j;
        int ret;

        writel(spmi_cmd, spmi->regs + SPMI_CMD_REG);

        while (i < len) {
                j = 0;
                spmi_cmd = 0;
                while ((j < 4) & (i < len))
                        spmi_cmd |= buf[i++] << (j++ * 8);

                writel(spmi_cmd, spmi->regs + SPMI_CMD_REG);
        }

        ret = apple_spmi_wait_rx_not_empty(ctrl);
        if (ret)
                return ret;

        /* Discard */
        readl(spmi->regs + SPMI_RSP_REG);

        return 0;
}

static int apple_spmi_probe(struct platform_device *pdev)
{
        struct apple_spmi *spmi;
        struct spmi_controller *ctrl;
        int ret;

        ctrl = devm_spmi_controller_alloc(&pdev->dev, sizeof(*spmi));
        if (IS_ERR(ctrl))
                return -ENOMEM;

        spmi = spmi_controller_get_drvdata(ctrl);

        spmi->regs = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(spmi->regs))
                return PTR_ERR(spmi->regs);

        ctrl->dev.of_node = pdev->dev.of_node;

        ctrl->read_cmd = spmi_read_cmd;
        ctrl->write_cmd = spmi_write_cmd;

        ret = devm_spmi_controller_add(&pdev->dev, ctrl);
        if (ret)
                return dev_err_probe(&pdev->dev, ret,
                                     "spmi_controller_add failed\n");

        return 0;
}

static const struct of_device_id apple_spmi_match_table[] = {
        { .compatible = "apple,t8103-spmi", },
        { .compatible = "apple,spmi", },
        {}
};
MODULE_DEVICE_TABLE(of, apple_spmi_match_table);

static struct platform_driver apple_spmi_driver = {
        .probe          = apple_spmi_probe,
        .driver         = {
                .name   = "apple-spmi",
                .of_match_table = apple_spmi_match_table,
        },
};
module_platform_driver(apple_spmi_driver);

MODULE_AUTHOR("Jean-Francois Bortolotti <jeff@borto.fr>");
MODULE_DESCRIPTION("Apple SoC SPMI driver");
MODULE_LICENSE("GPL");