/*
 * Copyright (C) 2017 Sanechips Technology Co., Ltd.
 * Copyright 2017 Linaro Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/clk.h>
#include <linux/component.h>
#include <linux/mfd/syscon.h>
#include <linux/regmap.h>

#include <drm/drm_atomic_helper.h>
#include <drm/drm_crtc_helper.h>
#include <drm/drmP.h>

#include "zx_drm_drv.h"
#include "zx_vga_regs.h"
#include "zx_vou.h"

struct zx_vga_pwrctrl {
        struct regmap *regmap;
        u32 reg;
        u32 mask;
};

struct zx_vga_i2c {
        struct i2c_adapter adap;
        struct mutex lock;
};

struct zx_vga {
        struct drm_connector connector;
        struct drm_encoder encoder;
        struct zx_vga_i2c *ddc;
        struct device *dev;
        void __iomem *mmio;
        struct clk *i2c_wclk;
        struct zx_vga_pwrctrl pwrctrl;
        struct completion complete;
        bool connected;
};

#define to_zx_vga(x) container_of(x, struct zx_vga, x)

static void zx_vga_encoder_enable(struct drm_encoder *encoder)
{
        struct zx_vga *vga = to_zx_vga(encoder);
        struct zx_vga_pwrctrl *pwrctrl = &vga->pwrctrl;

        /* Set bit to power up VGA DACs */
        regmap_update_bits(pwrctrl->regmap, pwrctrl->reg, pwrctrl->mask,
                           pwrctrl->mask);

        vou_inf_enable(VOU_VGA, encoder->crtc);
}

static void zx_vga_encoder_disable(struct drm_encoder *encoder)
{
        struct zx_vga *vga = to_zx_vga(encoder);
        struct zx_vga_pwrctrl *pwrctrl = &vga->pwrctrl;

        vou_inf_disable(VOU_VGA, encoder->crtc);

        /* Clear bit to power down VGA DACs */
        regmap_update_bits(pwrctrl->regmap, pwrctrl->reg, pwrctrl->mask, 0);
}

static const struct drm_encoder_helper_funcs zx_vga_encoder_helper_funcs = {
        .enable = zx_vga_encoder_enable,
        .disable = zx_vga_encoder_disable,
};

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

static int zx_vga_connector_get_modes(struct drm_connector *connector)
{
        struct zx_vga *vga = to_zx_vga(connector);
        struct edid *edid;
        int ret;

        /*
         * Clear both detection bits to switch I2C bus from device
         * detecting to EDID reading.
         */
        zx_writel(vga->mmio + VGA_AUTO_DETECT_SEL, 0);

        edid = drm_get_edid(connector, &vga->ddc->adap);
        if (!edid) {
                /*
                 * If EDID reading fails, we set the device state into
                 * disconnected.  Locking is not required here, since the
                 * VGA_AUTO_DETECT_SEL register write in irq handler cannot
                 * be triggered when both detection bits are cleared as above.
                 */
                zx_writel(vga->mmio + VGA_AUTO_DETECT_SEL,
                          VGA_DETECT_SEL_NO_DEVICE);
                vga->connected = false;
                return 0;
        }

        /*
         * As edid reading succeeds, device must be connected, so we set
         * up detection bit for unplug interrupt here.
         */
        zx_writel(vga->mmio + VGA_AUTO_DETECT_SEL, VGA_DETECT_SEL_HAS_DEVICE);

        drm_mode_connector_update_edid_property(connector, edid);
        ret = drm_add_edid_modes(connector, edid);
        kfree(edid);

        return ret;
}

static enum drm_mode_status
zx_vga_connector_mode_valid(struct drm_connector *connector,
                            struct drm_display_mode *mode)
{
        return MODE_OK;
}

static struct drm_connector_helper_funcs zx_vga_connector_helper_funcs = {
        .get_modes = zx_vga_connector_get_modes,
        .mode_valid = zx_vga_connector_mode_valid,
};

static enum drm_connector_status
zx_vga_connector_detect(struct drm_connector *connector, bool force)
{
        struct zx_vga *vga = to_zx_vga(connector);

        return vga->connected ? connector_status_connected :
                                connector_status_disconnected;
}

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

static int zx_vga_register(struct drm_device *drm, struct zx_vga *vga)
{
        struct drm_encoder *encoder = &vga->encoder;
        struct drm_connector *connector = &vga->connector;
        struct device *dev = vga->dev;
        int ret;

        encoder->possible_crtcs = VOU_CRTC_MASK;

        ret = drm_encoder_init(drm, encoder, &zx_vga_encoder_funcs,
                               DRM_MODE_ENCODER_DAC, NULL);
        if (ret) {
                DRM_DEV_ERROR(dev, "failed to init encoder: %d\n", ret);
                return ret;
        };

        drm_encoder_helper_add(encoder, &zx_vga_encoder_helper_funcs);

        vga->connector.polled = DRM_CONNECTOR_POLL_HPD;

        ret = drm_connector_init(drm, connector, &zx_vga_connector_funcs,
                                 DRM_MODE_CONNECTOR_VGA);
        if (ret) {
                DRM_DEV_ERROR(dev, "failed to init connector: %d\n", ret);
                goto clean_encoder;
        };

        drm_connector_helper_add(connector, &zx_vga_connector_helper_funcs);

        ret = drm_mode_connector_attach_encoder(connector, encoder);
        if (ret) {
                DRM_DEV_ERROR(dev, "failed to attach encoder: %d\n", ret);
                goto clean_connector;
        };

        return 0;

clean_connector:
        drm_connector_cleanup(connector);
clean_encoder:
        drm_encoder_cleanup(encoder);
        return ret;
}

static int zx_vga_pwrctrl_init(struct zx_vga *vga)
{
        struct zx_vga_pwrctrl *pwrctrl = &vga->pwrctrl;
        struct device *dev = vga->dev;
        struct of_phandle_args out_args;
        struct regmap *regmap;
        int ret;

        ret = of_parse_phandle_with_fixed_args(dev->of_node,
                                "zte,vga-power-control", 2, 0, &out_args);
        if (ret)
                return ret;

        regmap = syscon_node_to_regmap(out_args.np);
        if (IS_ERR(regmap)) {
                ret = PTR_ERR(regmap);
                goto out;
        }

        pwrctrl->regmap = regmap;
        pwrctrl->reg = out_args.args[0];
        pwrctrl->mask = out_args.args[1];

out:
        of_node_put(out_args.np);
        return ret;
}

static int zx_vga_i2c_read(struct zx_vga *vga, struct i2c_msg *msg)
{
        int len = msg->len;
        u8 *buf = msg->buf;
        u32 offset = 0;
        int i;

        reinit_completion(&vga->complete);

        /* Select combo write */
        zx_writel_mask(vga->mmio + VGA_CMD_CFG, VGA_CMD_COMBO, VGA_CMD_COMBO);
        zx_writel_mask(vga->mmio + VGA_CMD_CFG, VGA_CMD_RW, 0);

        while (len > 0) {
                u32 cnt;

                /* Clear RX FIFO */
                zx_writel_mask(vga->mmio + VGA_RXF_CTRL, VGA_RX_FIFO_CLEAR,
                               VGA_RX_FIFO_CLEAR);

                /* Data offset to read from */
                zx_writel(vga->mmio + VGA_SUB_ADDR, offset);

                /* Kick off the transfer */
                zx_writel_mask(vga->mmio + VGA_CMD_CFG, VGA_CMD_TRANS,
                               VGA_CMD_TRANS);

                if (!wait_for_completion_timeout(&vga->complete,
                                                 msecs_to_jiffies(1000))) {
                        DRM_DEV_ERROR(vga->dev, "transfer timeout\n");
                        return -ETIMEDOUT;
                }

                cnt = zx_readl(vga->mmio + VGA_RXF_STATUS);
                cnt = (cnt & VGA_RXF_COUNT_MASK) >> VGA_RXF_COUNT_SHIFT;
                /* FIFO status may report more data than we need to read */
                cnt = min_t(u32, len, cnt);

                for (i = 0; i < cnt; i++)
                        *buf++ = zx_readl(vga->mmio + VGA_DATA);

                len -= cnt;
                offset += cnt;
        }

        return 0;
}

static int zx_vga_i2c_write(struct zx_vga *vga, struct i2c_msg *msg)
{
        /*
         * The DDC I2C adapter is only for reading EDID data, so we assume
         * that the write to this adapter must be the EDID data offset.
         */
        if ((msg->len != 1) || ((msg->addr != DDC_ADDR)))
                return -EINVAL;

        /* Hardware will take care of the slave address shifting */
        zx_writel(vga->mmio + VGA_DEVICE_ADDR, msg->addr);

        return 0;
}

static int zx_vga_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                           int num)
{
        struct zx_vga *vga = i2c_get_adapdata(adap);
        struct zx_vga_i2c *ddc = vga->ddc;
        int ret = 0;
        int i;

        mutex_lock(&ddc->lock);

        for (i = 0; i < num; i++) {
                if (msgs[i].flags & I2C_M_RD)
                        ret = zx_vga_i2c_read(vga, &msgs[i]);
                else
                        ret = zx_vga_i2c_write(vga, &msgs[i]);

                if (ret < 0)
                        break;
        }

        if (!ret)
                ret = num;

        mutex_unlock(&ddc->lock);

        return ret;
}

static u32 zx_vga_i2c_func(struct i2c_adapter *adapter)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static const struct i2c_algorithm zx_vga_algorithm = {
        .master_xfer    = zx_vga_i2c_xfer,
        .functionality  = zx_vga_i2c_func,
};

static int zx_vga_ddc_register(struct zx_vga *vga)
{
        struct device *dev = vga->dev;
        struct i2c_adapter *adap;
        struct zx_vga_i2c *ddc;
        int ret;

        ddc = devm_kzalloc(dev, sizeof(*ddc), GFP_KERNEL);
        if (!ddc)
                return -ENOMEM;

        vga->ddc = ddc;
        mutex_init(&ddc->lock);

        adap = &ddc->adap;
        adap->owner = THIS_MODULE;
        adap->class = I2C_CLASS_DDC;
        adap->dev.parent = dev;
        adap->algo = &zx_vga_algorithm;
        snprintf(adap->name, sizeof(adap->name), "zx vga i2c");

        ret = i2c_add_adapter(adap);
        if (ret) {
                DRM_DEV_ERROR(dev, "failed to add I2C adapter: %d\n", ret);
                return ret;
        }

        i2c_set_adapdata(adap, vga);

        return 0;
}

static irqreturn_t zx_vga_irq_thread(int irq, void *dev_id)
{
        struct zx_vga *vga = dev_id;

        drm_helper_hpd_irq_event(vga->connector.dev);

        return IRQ_HANDLED;
}

static irqreturn_t zx_vga_irq_handler(int irq, void *dev_id)
{
        struct zx_vga *vga = dev_id;
        u32 status;

        status = zx_readl(vga->mmio + VGA_I2C_STATUS);

        /* Clear interrupt status */
        zx_writel_mask(vga->mmio + VGA_I2C_STATUS, VGA_CLEAR_IRQ,
                       VGA_CLEAR_IRQ);

        if (status & VGA_DEVICE_CONNECTED) {
                /*
                 * Since VGA_DETECT_SEL bits need to be reset for switching DDC
                 * bus from device detection to EDID read, rather than setting
                 * up HAS_DEVICE bit here, we need to do that in .get_modes
                 * hook for unplug detecting after EDID read succeeds.
                 */
                vga->connected = true;
                return IRQ_WAKE_THREAD;
        }

        if (status & VGA_DEVICE_DISCONNECTED) {
                zx_writel(vga->mmio + VGA_AUTO_DETECT_SEL,
                          VGA_DETECT_SEL_NO_DEVICE);
                vga->connected = false;
                return IRQ_WAKE_THREAD;
        }

        if (status & VGA_TRANS_DONE) {
                complete(&vga->complete);
                return IRQ_HANDLED;
        }

        return IRQ_NONE;
}

static void zx_vga_hw_init(struct zx_vga *vga)
{
        unsigned long ref = clk_get_rate(vga->i2c_wclk);
        int div;

        /*
         * Set up I2C fast speed divider per formula below to get 400kHz.
         *   scl = ref / ((div + 1) * 4)
         */
        div = DIV_ROUND_UP(ref / 1000, 400 * 4) - 1;
        zx_writel(vga->mmio + VGA_CLK_DIV_FS, div);

        /* Set up device detection */
        zx_writel(vga->mmio + VGA_AUTO_DETECT_PARA, 0x80);
        zx_writel(vga->mmio + VGA_AUTO_DETECT_SEL, VGA_DETECT_SEL_NO_DEVICE);

        /*
         * We need to poke monitor via DDC bus to get connection irq
         * start working.
         */
        zx_writel(vga->mmio + VGA_DEVICE_ADDR, DDC_ADDR);
        zx_writel_mask(vga->mmio + VGA_CMD_CFG, VGA_CMD_TRANS, VGA_CMD_TRANS);
}

static int zx_vga_bind(struct device *dev, struct device *master, void *data)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct drm_device *drm = data;
        struct resource *res;
        struct zx_vga *vga;
        int irq;
        int ret;

        vga = devm_kzalloc(dev, sizeof(*vga), GFP_KERNEL);
        if (!vga)
                return -ENOMEM;

        vga->dev = dev;
        dev_set_drvdata(dev, vga);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        vga->mmio = devm_ioremap_resource(dev, res);
        if (IS_ERR(vga->mmio))
                return PTR_ERR(vga->mmio);

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        vga->i2c_wclk = devm_clk_get(dev, "i2c_wclk");
        if (IS_ERR(vga->i2c_wclk)) {
                ret = PTR_ERR(vga->i2c_wclk);
                DRM_DEV_ERROR(dev, "failed to get i2c_wclk: %d\n", ret);
                return ret;
        }

        ret = zx_vga_pwrctrl_init(vga);
        if (ret) {
                DRM_DEV_ERROR(dev, "failed to init power control: %d\n", ret);
                return ret;
        }

        ret = zx_vga_ddc_register(vga);
        if (ret) {
                DRM_DEV_ERROR(dev, "failed to register ddc: %d\n", ret);
                return ret;
        }

        ret = zx_vga_register(drm, vga);
        if (ret) {
                DRM_DEV_ERROR(dev, "failed to register vga: %d\n", ret);
                return ret;
        }

        init_completion(&vga->complete);

        ret = devm_request_threaded_irq(dev, irq, zx_vga_irq_handler,
                                        zx_vga_irq_thread, IRQF_SHARED,
                                        dev_name(dev), vga);
        if (ret) {
                DRM_DEV_ERROR(dev, "failed to request threaded irq: %d\n", ret);
                return ret;
        }

        ret = clk_prepare_enable(vga->i2c_wclk);
        if (ret)
                return ret;

        zx_vga_hw_init(vga);

        return 0;
}

static void zx_vga_unbind(struct device *dev, struct device *master,
                          void *data)
{
        struct zx_vga *vga = dev_get_drvdata(dev);

        clk_disable_unprepare(vga->i2c_wclk);
}

static const struct component_ops zx_vga_component_ops = {
        .bind = zx_vga_bind,
        .unbind = zx_vga_unbind,
};

static int zx_vga_probe(struct platform_device *pdev)
{
        return component_add(&pdev->dev, &zx_vga_component_ops);
}

static int zx_vga_remove(struct platform_device *pdev)
{
        component_del(&pdev->dev, &zx_vga_component_ops);
        return 0;
}

static const struct of_device_id zx_vga_of_match[] = {
        { .compatible = "zte,zx296718-vga", },
        { /* end */ },
};
MODULE_DEVICE_TABLE(of, zx_vga_of_match);

struct platform_driver zx_vga_driver = {
        .probe = zx_vga_probe,
        .remove = zx_vga_remove,
        .driver = {
                .name = "zx-vga",
                .of_match_table = zx_vga_of_match,
        },
};