/*
 * Copyright © 2016 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#include <linux/errno.h>
#include <linux/export.h>
#include <linux/i2c.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <drm/drm_dp_dual_mode_helper.h>
#include <drm/drmP.h>

/**
 * DOC: dp dual mode helpers
 *
 * Helper functions to deal with DP dual mode (aka. DP++) adaptors.
 *
 * Type 1:
 * Adaptor registers (if any) and the sink DDC bus may be accessed via I2C.
 *
 * Type 2:
 * Adaptor registers and sink DDC bus can be accessed either via I2C or
 * I2C-over-AUX. Source devices may choose to implement either of these
 * access methods.
 */

#define DP_DUAL_MODE_SLAVE_ADDRESS 0x40

/**
 * drm_dp_dual_mode_read - Read from the DP dual mode adaptor register(s)
 * @adapter: I2C adapter for the DDC bus
 * @offset: register offset
 * @buffer: buffer for return data
 * @size: sizo of the buffer
 *
 * Reads @size bytes from the DP dual mode adaptor registers
 * starting at @offset.
 *
 * Returns:
 * 0 on success, negative error code on failure
 */
ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
                              u8 offset, void *buffer, size_t size)
{
        struct i2c_msg msgs[] = {
                {
                        .addr = DP_DUAL_MODE_SLAVE_ADDRESS,
                        .flags = 0,
                        .len = 1,
                        .buf = &offset,
                },
                {
                        .addr = DP_DUAL_MODE_SLAVE_ADDRESS,
                        .flags = I2C_M_RD,
                        .len = size,
                        .buf = buffer,
                },
        };
        int ret;

        ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
        if (ret < 0)
                return ret;
        if (ret != ARRAY_SIZE(msgs))
                return -EPROTO;

        return 0;
}
EXPORT_SYMBOL(drm_dp_dual_mode_read);

/**
 * drm_dp_dual_mode_write - Write to the DP dual mode adaptor register(s)
 * @adapter: I2C adapter for the DDC bus
 * @offset: register offset
 * @buffer: buffer for write data
 * @size: sizo of the buffer
 *
 * Writes @size bytes to the DP dual mode adaptor registers
 * starting at @offset.
 *
 * Returns:
 * 0 on success, negative error code on failure
 */
ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
                               u8 offset, const void *buffer, size_t size)
{
        struct i2c_msg msg = {
                .addr = DP_DUAL_MODE_SLAVE_ADDRESS,
                .flags = 0,
                .len = 1 + size,
                .buf = NULL,
        };
        void *data;
        int ret;

        data = kmalloc(msg.len, GFP_TEMPORARY);
        if (!data)
                return -ENOMEM;

        msg.buf = data;

        memcpy(data, &offset, 1);
        memcpy(data + 1, buffer, size);

        ret = i2c_transfer(adapter, &msg, 1);

        kfree(data);

        if (ret < 0)
                return ret;
        if (ret != 1)
                return -EPROTO;

        return 0;
}
EXPORT_SYMBOL(drm_dp_dual_mode_write);

static bool is_hdmi_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])
{
        static const char dp_dual_mode_hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] =
                "DP-HDMI ADAPTOR\x04";

        return memcmp(hdmi_id, dp_dual_mode_hdmi_id,
                      sizeof(dp_dual_mode_hdmi_id)) == 0;
}

static bool is_type1_adaptor(uint8_t adaptor_id)
{
        return adaptor_id == 0 || adaptor_id == 0xff;
}

static bool is_type2_adaptor(uint8_t adaptor_id)
{
        return adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
                              DP_DUAL_MODE_REV_TYPE2);
}

static bool is_lspcon_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN],
                              const uint8_t adaptor_id)
{
        return is_hdmi_adaptor(hdmi_id) &&
                (adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
                 DP_DUAL_MODE_TYPE_HAS_DPCD));
}

/**
 * drm_dp_dual_mode_detect - Identify the DP dual mode adaptor
 * @adapter: I2C adapter for the DDC bus
 *
 * Attempt to identify the type of the DP dual mode adaptor used.
 *
 * Note that when the answer is @DRM_DP_DUAL_MODE_UNKNOWN it's not
 * certain whether we're dealing with a native HDMI port or
 * a type 1 DVI dual mode adaptor. The driver will have to use
 * some other hardware/driver specific mechanism to make that
 * distinction.
 *
 * Returns:
 * The type of the DP dual mode adaptor used
 */
enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
{
        char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] = {};
        uint8_t adaptor_id = 0x00;
        ssize_t ret;

        /*
         * Let's see if the adaptor is there the by reading the
         * HDMI ID registers.
         *
         * Note that type 1 DVI adaptors are not required to implemnt
         * any registers, and that presents a problem for detection.
         * If the i2c transfer is nacked, we may or may not be dealing
         * with a type 1 DVI adaptor. Some other mechanism of detecting
         * the presence of the adaptor is required. One way would be
         * to check the state of the CONFIG1 pin, Another method would
         * simply require the driver to know whether the port is a DP++
         * port or a native HDMI port. Both of these methods are entirely
         * hardware/driver specific so we can't deal with them here.
         */
        ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,
                                    hdmi_id, sizeof(hdmi_id));
        DRM_DEBUG_KMS("DP dual mode HDMI ID: %*pE (err %zd)\n",
                      ret ? 0 : (int)sizeof(hdmi_id), hdmi_id, ret);
        if (ret)
                return DRM_DP_DUAL_MODE_UNKNOWN;

        /*
         * Sigh. Some (maybe all?) type 1 adaptors are broken and ack
         * the offset but ignore it, and instead they just always return
         * data from the start of the HDMI ID buffer. So for a broken
         * type 1 HDMI adaptor a single byte read will always give us
         * 0x44, and for a type 1 DVI adaptor it should give 0x00
         * (assuming it implements any registers). Fortunately neither
         * of those values will match the type 2 signature of the
         * DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with
         * the type 2 adaptor detection safely even in the presence
         * of broken type 1 adaptors.
         */
        ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
                                    &adaptor_id, sizeof(adaptor_id));
        DRM_DEBUG_KMS("DP dual mode adaptor ID: %02x (err %zd)\n",
                      adaptor_id, ret);
        if (ret == 0) {
                if (is_lspcon_adaptor(hdmi_id, adaptor_id))
                        return DRM_DP_DUAL_MODE_LSPCON;
                if (is_type2_adaptor(adaptor_id)) {
                        if (is_hdmi_adaptor(hdmi_id))
                                return DRM_DP_DUAL_MODE_TYPE2_HDMI;
                        else
                                return DRM_DP_DUAL_MODE_TYPE2_DVI;
                }
                /*
                 * If neither a proper type 1 ID nor a broken type 1 adaptor
                 * as described above, assume type 1, but let the user know
                 * that we may have misdetected the type.
                 */
                if (!is_type1_adaptor(adaptor_id) && adaptor_id != hdmi_id[0])
                        DRM_ERROR("Unexpected DP dual mode adaptor ID %02x\n",
                                  adaptor_id);

        }

        if (is_hdmi_adaptor(hdmi_id))
                return DRM_DP_DUAL_MODE_TYPE1_HDMI;
        else
                return DRM_DP_DUAL_MODE_TYPE1_DVI;
}
EXPORT_SYMBOL(drm_dp_dual_mode_detect);

/**
 * drm_dp_dual_mode_max_tmds_clock - Max TMDS clock for DP dual mode adaptor
 * @type: DP dual mode adaptor type
 * @adapter: I2C adapter for the DDC bus
 *
 * Determine the max TMDS clock the adaptor supports based on the
 * type of the dual mode adaptor and the DP_DUAL_MODE_MAX_TMDS_CLOCK
 * register (on type2 adaptors). As some type 1 adaptors have
 * problems with registers (see comments in drm_dp_dual_mode_detect())
 * we don't read the register on those, instead we simply assume
 * a 165 MHz limit based on the specification.
 *
 * Returns:
 * Maximum supported TMDS clock rate for the DP dual mode adaptor in kHz.
 */
int drm_dp_dual_mode_max_tmds_clock(enum drm_dp_dual_mode_type type,
                                    struct i2c_adapter *adapter)
{
        uint8_t max_tmds_clock;
        ssize_t ret;

        /* native HDMI so no limit */
        if (type == DRM_DP_DUAL_MODE_NONE)
                return 0;

        /*
         * Type 1 adaptors are limited to 165MHz
         * Type 2 adaptors can tells us their limit
         */
        if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
                return 165000;

        ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_MAX_TMDS_CLOCK,
                                    &max_tmds_clock, sizeof(max_tmds_clock));
        if (ret || max_tmds_clock == 0x00 || max_tmds_clock == 0xff) {
                DRM_DEBUG_KMS("Failed to query max TMDS clock\n");
                return 165000;
        }

        return max_tmds_clock * 5000 / 2;
}
EXPORT_SYMBOL(drm_dp_dual_mode_max_tmds_clock);

/**
 * drm_dp_dual_mode_get_tmds_output - Get the state of the TMDS output buffers in the DP dual mode adaptor
 * @type: DP dual mode adaptor type
 * @adapter: I2C adapter for the DDC bus
 * @enabled: current state of the TMDS output buffers
 *
 * Get the state of the TMDS output buffers in the adaptor. For
 * type2 adaptors this is queried from the DP_DUAL_MODE_TMDS_OEN
 * register. As some type 1 adaptors have problems with registers
 * (see comments in drm_dp_dual_mode_detect()) we don't read the
 * register on those, instead we simply assume that the buffers
 * are always enabled.
 *
 * Returns:
 * 0 on success, negative error code on failure
 */
int drm_dp_dual_mode_get_tmds_output(enum drm_dp_dual_mode_type type,
                                     struct i2c_adapter *adapter,
                                     bool *enabled)
{
        uint8_t tmds_oen;
        ssize_t ret;

        if (type < DRM_DP_DUAL_MODE_TYPE2_DVI) {
                *enabled = true;
                return 0;
        }

        ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_TMDS_OEN,
                                    &tmds_oen, sizeof(tmds_oen));
        if (ret) {
                DRM_DEBUG_KMS("Failed to query state of TMDS output buffers\n");
                return ret;
        }

        *enabled = !(tmds_oen & DP_DUAL_MODE_TMDS_DISABLE);

        return 0;
}
EXPORT_SYMBOL(drm_dp_dual_mode_get_tmds_output);

/**
 * drm_dp_dual_mode_set_tmds_output - Enable/disable TMDS output buffers in the DP dual mode adaptor
 * @type: DP dual mode adaptor type
 * @adapter: I2C adapter for the DDC bus
 * @enable: enable (as opposed to disable) the TMDS output buffers
 *
 * Set the state of the TMDS output buffers in the adaptor. For
 * type2 this is set via the DP_DUAL_MODE_TMDS_OEN register. As
 * some type 1 adaptors have problems with registers (see comments
 * in drm_dp_dual_mode_detect()) we avoid touching the register,
 * making this function a no-op on type 1 adaptors.
 *
 * Returns:
 * 0 on success, negative error code on failure
 */
int drm_dp_dual_mode_set_tmds_output(enum drm_dp_dual_mode_type type,
                                     struct i2c_adapter *adapter, bool enable)
{
        uint8_t tmds_oen = enable ? 0 : DP_DUAL_MODE_TMDS_DISABLE;
        ssize_t ret;

        if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
                return 0;

        ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_TMDS_OEN,
                                     &tmds_oen, sizeof(tmds_oen));
        if (ret) {
                DRM_DEBUG_KMS("Failed to %s TMDS output buffers\n",
                              enable ? "enable" : "disable");
                return ret;
        }

        return 0;
}
EXPORT_SYMBOL(drm_dp_dual_mode_set_tmds_output);

/**
 * drm_dp_get_dual_mode_type_name - Get the name of the DP dual mode adaptor type as a string
 * @type: DP dual mode adaptor type
 *
 * Returns:
 * String representation of the DP dual mode adaptor type
 */
const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type)
{
        switch (type) {
        case DRM_DP_DUAL_MODE_NONE:
                return "none";
        case DRM_DP_DUAL_MODE_TYPE1_DVI:
                return "type 1 DVI";
        case DRM_DP_DUAL_MODE_TYPE1_HDMI:
                return "type 1 HDMI";
        case DRM_DP_DUAL_MODE_TYPE2_DVI:
                return "type 2 DVI";
        case DRM_DP_DUAL_MODE_TYPE2_HDMI:
                return "type 2 HDMI";
        case DRM_DP_DUAL_MODE_LSPCON:
                return "lspcon";
        default:
                WARN_ON(type != DRM_DP_DUAL_MODE_UNKNOWN);
                return "unknown";
        }
}
EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);

/**
 * drm_lspcon_get_mode: Get LSPCON's current mode of operation by
 * reading offset (0x80, 0x41)
 * @adapter: I2C-over-aux adapter
 * @mode: current lspcon mode of operation output variable
 *
 * Returns:
 * 0 on success, sets the current_mode value to appropriate mode
 * -error on failure
 */
int drm_lspcon_get_mode(struct i2c_adapter *adapter,
                        enum drm_lspcon_mode *mode)
{
        u8 data;
        int ret = 0;

        if (!mode) {
                DRM_ERROR("NULL input\n");
                return -EINVAL;
        }

        /* Read Status: i2c over aux */
        ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE,
                                    &data, sizeof(data));
        if (ret < 0) {
                DRM_ERROR("LSPCON read(0x80, 0x41) failed\n");
                return -EFAULT;
        }

        if (data & DP_DUAL_MODE_LSPCON_MODE_PCON)
                *mode = DRM_LSPCON_MODE_PCON;
        else
                *mode = DRM_LSPCON_MODE_LS;
        return 0;
}
EXPORT_SYMBOL(drm_lspcon_get_mode);

/**
 * drm_lspcon_set_mode: Change LSPCON's mode of operation by
 * writing offset (0x80, 0x40)
 * @adapter: I2C-over-aux adapter
 * @mode: required mode of operation
 *
 * Returns:
 * 0 on success, -error on failure/timeout
 */
int drm_lspcon_set_mode(struct i2c_adapter *adapter,
                        enum drm_lspcon_mode mode)
{
        u8 data = 0;
        int ret;
        int time_out = 200;
        enum drm_lspcon_mode current_mode;

        if (mode == DRM_LSPCON_MODE_PCON)
                data = DP_DUAL_MODE_LSPCON_MODE_PCON;

        /* Change mode */
        ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_LSPCON_MODE_CHANGE,
                                     &data, sizeof(data));
        if (ret < 0) {
                DRM_ERROR("LSPCON mode change failed\n");
                return ret;
        }

        /*
         * Confirm mode change by reading the status bit.
         * Sometimes, it takes a while to change the mode,
         * so wait and retry until time out or done.
         */
        do {
                ret = drm_lspcon_get_mode(adapter, &current_mode);
                if (ret) {
                        DRM_ERROR("can't confirm LSPCON mode change\n");
                        return ret;
                } else {
                        if (current_mode != mode) {
                                msleep(10);
                                time_out -= 10;
                        } else {
                                DRM_DEBUG_KMS("LSPCON mode changed to %s\n",
                                                mode == DRM_LSPCON_MODE_LS ?
                                                "LS" : "PCON");
                                return 0;
                        }
                }
        } while (time_out);

        DRM_ERROR("LSPCON mode change timed out\n");
        return -ETIMEDOUT;
}
EXPORT_SYMBOL(drm_lspcon_set_mode);