root/drivers/gpu/drm/msm/hdmi/hdmi_i2c.c
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2013 Red Hat
 * Author: Rob Clark <robdclark@gmail.com>
 */

#include "hdmi.h"

struct hdmi_i2c_adapter {
        struct i2c_adapter base;
        struct hdmi *hdmi;
        bool sw_done;
        wait_queue_head_t ddc_event;
};
#define to_hdmi_i2c_adapter(x) container_of(x, struct hdmi_i2c_adapter, base)

static void init_ddc(struct hdmi_i2c_adapter *hdmi_i2c)
{
        struct hdmi *hdmi = hdmi_i2c->hdmi;

        hdmi_write(hdmi, REG_HDMI_DDC_CTRL,
                        HDMI_DDC_CTRL_SW_STATUS_RESET);
        hdmi_write(hdmi, REG_HDMI_DDC_CTRL,
                        HDMI_DDC_CTRL_SOFT_RESET);

        hdmi_write(hdmi, REG_HDMI_DDC_SPEED,
                        HDMI_DDC_SPEED_THRESHOLD(2) |
                        HDMI_DDC_SPEED_PRESCALE(10));

        hdmi_write(hdmi, REG_HDMI_DDC_SETUP,
                        HDMI_DDC_SETUP_TIMEOUT(0xff));

        /* enable reference timer for 27us */
        hdmi_write(hdmi, REG_HDMI_DDC_REF,
                        HDMI_DDC_REF_REFTIMER_ENABLE |
                        HDMI_DDC_REF_REFTIMER(27));
}

static int ddc_clear_irq(struct hdmi_i2c_adapter *hdmi_i2c)
{
        struct hdmi *hdmi = hdmi_i2c->hdmi;
        struct drm_device *dev = hdmi->dev;
        uint32_t retry = 0xffff;
        uint32_t ddc_int_ctrl;

        do {
                --retry;

                hdmi_write(hdmi, REG_HDMI_DDC_INT_CTRL,
                                HDMI_DDC_INT_CTRL_SW_DONE_ACK |
                                HDMI_DDC_INT_CTRL_SW_DONE_MASK);

                ddc_int_ctrl = hdmi_read(hdmi, REG_HDMI_DDC_INT_CTRL);

        } while ((ddc_int_ctrl & HDMI_DDC_INT_CTRL_SW_DONE_INT) && retry);

        if (!retry) {
                DRM_DEV_ERROR(dev->dev, "timeout waiting for DDC\n");
                return -ETIMEDOUT;
        }

        hdmi_i2c->sw_done = false;

        return 0;
}

#define MAX_TRANSACTIONS 4

static bool sw_done(struct hdmi_i2c_adapter *hdmi_i2c)
{
        struct hdmi *hdmi = hdmi_i2c->hdmi;

        if (!hdmi_i2c->sw_done) {
                uint32_t ddc_int_ctrl;

                ddc_int_ctrl = hdmi_read(hdmi, REG_HDMI_DDC_INT_CTRL);

                if ((ddc_int_ctrl & HDMI_DDC_INT_CTRL_SW_DONE_MASK) &&
                                (ddc_int_ctrl & HDMI_DDC_INT_CTRL_SW_DONE_INT)) {
                        hdmi_i2c->sw_done = true;
                        hdmi_write(hdmi, REG_HDMI_DDC_INT_CTRL,
                                        HDMI_DDC_INT_CTRL_SW_DONE_ACK);
                }
        }

        return hdmi_i2c->sw_done;
}

static int msm_hdmi_i2c_xfer(struct i2c_adapter *i2c,
                struct i2c_msg *msgs, int num)
{
        struct hdmi_i2c_adapter *hdmi_i2c = to_hdmi_i2c_adapter(i2c);
        struct hdmi *hdmi = hdmi_i2c->hdmi;
        struct drm_device *dev = hdmi->dev;
        static const uint32_t nack[] = {
                        HDMI_DDC_SW_STATUS_NACK0, HDMI_DDC_SW_STATUS_NACK1,
                        HDMI_DDC_SW_STATUS_NACK2, HDMI_DDC_SW_STATUS_NACK3,
        };
        int indices[MAX_TRANSACTIONS];
        int ret, i, j, index = 0;
        uint32_t ddc_status, ddc_data, i2c_trans;

        num = min(num, MAX_TRANSACTIONS);

        WARN_ON(!(hdmi_read(hdmi, REG_HDMI_CTRL) & HDMI_CTRL_ENABLE));

        if (num == 0)
                return num;

        ret = pm_runtime_resume_and_get(&hdmi->pdev->dev);
        if (ret)
                return ret;

        init_ddc(hdmi_i2c);

        ret = ddc_clear_irq(hdmi_i2c);
        if (ret)
                goto fail;

        for (i = 0; i < num; i++) {
                struct i2c_msg *p = &msgs[i];
                uint32_t raw_addr = p->addr << 1;

                if (p->flags & I2C_M_RD)
                        raw_addr |= 1;

                ddc_data = HDMI_DDC_DATA_DATA(raw_addr) |
                                HDMI_DDC_DATA_DATA_RW(DDC_WRITE);

                if (i == 0) {
                        ddc_data |= HDMI_DDC_DATA_INDEX(0) |
                                        HDMI_DDC_DATA_INDEX_WRITE;
                }

                hdmi_write(hdmi, REG_HDMI_DDC_DATA, ddc_data);
                index++;

                indices[i] = index;

                if (p->flags & I2C_M_RD) {
                        index += p->len;
                } else {
                        for (j = 0; j < p->len; j++) {
                                ddc_data = HDMI_DDC_DATA_DATA(p->buf[j]) |
                                                HDMI_DDC_DATA_DATA_RW(DDC_WRITE);
                                hdmi_write(hdmi, REG_HDMI_DDC_DATA, ddc_data);
                                index++;
                        }
                }

                i2c_trans = HDMI_I2C_TRANSACTION_REG_CNT(p->len) |
                                HDMI_I2C_TRANSACTION_REG_RW(
                                                (p->flags & I2C_M_RD) ? DDC_READ : DDC_WRITE) |
                                HDMI_I2C_TRANSACTION_REG_START;

                if (i == (num - 1))
                        i2c_trans |= HDMI_I2C_TRANSACTION_REG_STOP;

                hdmi_write(hdmi, REG_HDMI_I2C_TRANSACTION(i), i2c_trans);
        }

        /* trigger the transfer: */
        hdmi_write(hdmi, REG_HDMI_DDC_CTRL,
                        HDMI_DDC_CTRL_TRANSACTION_CNT(num - 1) |
                        HDMI_DDC_CTRL_GO);

        ret = wait_event_timeout(hdmi_i2c->ddc_event, sw_done(hdmi_i2c), HZ/4);
        if (ret <= 0) {
                if (ret == 0)
                        ret = -ETIMEDOUT;
                dev_warn(dev->dev, "DDC timeout: %d\n", ret);
                DBG("sw_status=%08x, hw_status=%08x, int_ctrl=%08x",
                                hdmi_read(hdmi, REG_HDMI_DDC_SW_STATUS),
                                hdmi_read(hdmi, REG_HDMI_DDC_HW_STATUS),
                                hdmi_read(hdmi, REG_HDMI_DDC_INT_CTRL));
                goto fail;
        }

        ddc_status = hdmi_read(hdmi, REG_HDMI_DDC_SW_STATUS);

        /* read back results of any read transactions: */
        for (i = 0; i < num; i++) {
                struct i2c_msg *p = &msgs[i];

                if (!(p->flags & I2C_M_RD))
                        continue;

                /* check for NACK: */
                if (ddc_status & nack[i]) {
                        DBG("ddc_status=%08x", ddc_status);
                        break;
                }

                ddc_data = HDMI_DDC_DATA_DATA_RW(DDC_READ) |
                                HDMI_DDC_DATA_INDEX(indices[i]) |
                                HDMI_DDC_DATA_INDEX_WRITE;

                hdmi_write(hdmi, REG_HDMI_DDC_DATA, ddc_data);

                /* discard first byte: */
                hdmi_read(hdmi, REG_HDMI_DDC_DATA);

                for (j = 0; j < p->len; j++) {
                        ddc_data = hdmi_read(hdmi, REG_HDMI_DDC_DATA);
                        p->buf[j] = FIELD(ddc_data, HDMI_DDC_DATA_DATA);
                }
        }

        pm_runtime_put(&hdmi->pdev->dev);

        return i;

fail:
        pm_runtime_put(&hdmi->pdev->dev);
        return ret;
}

static u32 msm_hdmi_i2c_func(struct i2c_adapter *adapter)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static const struct i2c_algorithm msm_hdmi_i2c_algorithm = {
        .master_xfer    = msm_hdmi_i2c_xfer,
        .functionality  = msm_hdmi_i2c_func,
};

void msm_hdmi_i2c_irq(struct i2c_adapter *i2c)
{
        struct hdmi_i2c_adapter *hdmi_i2c = to_hdmi_i2c_adapter(i2c);

        if (sw_done(hdmi_i2c))
                wake_up_all(&hdmi_i2c->ddc_event);
}

void msm_hdmi_i2c_destroy(struct i2c_adapter *i2c)
{
        struct hdmi_i2c_adapter *hdmi_i2c = to_hdmi_i2c_adapter(i2c);
        i2c_del_adapter(i2c);
        kfree(hdmi_i2c);
}

struct i2c_adapter *msm_hdmi_i2c_init(struct hdmi *hdmi)
{
        struct hdmi_i2c_adapter *hdmi_i2c;
        struct i2c_adapter *i2c = NULL;
        int ret;

        hdmi_i2c = kzalloc_obj(*hdmi_i2c);
        if (!hdmi_i2c) {
                ret = -ENOMEM;
                goto fail;
        }

        i2c = &hdmi_i2c->base;

        hdmi_i2c->hdmi = hdmi;
        init_waitqueue_head(&hdmi_i2c->ddc_event);


        i2c->owner = THIS_MODULE;
        snprintf(i2c->name, sizeof(i2c->name), "msm hdmi i2c");
        i2c->dev.parent = &hdmi->pdev->dev;
        i2c->algo = &msm_hdmi_i2c_algorithm;

        ret = i2c_add_adapter(i2c);
        if (ret)
                goto fail;

        return i2c;

fail:
        if (i2c)
                msm_hdmi_i2c_destroy(i2c);
        return ERR_PTR(ret);
}