drivers/gpu/drm/drm_scdc_helper.c - arm/linux - Git at Google

 /*
  * Copyright (c) 2015 NVIDIA Corporation. All rights reserved.
  *
  * 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, sub license,
  * 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 (including the
  * next paragraph) 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 NON-INFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS 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/slab.h>
 #include <linux/delay.h>

 #include <drm/drm_scdc_helper.h>
 #include <drm/drmP.h>

 /**
  * DOC: scdc helpers
  *
  * Status and Control Data Channel (SCDC) is a mechanism introduced by the
  * HDMI 2.0 specification. It is a point-to-point protocol that allows the
  * HDMI source and HDMI sink to exchange data. The same I2C interface that
  * is used to access EDID serves as the transport mechanism for SCDC.
  */

 #define SCDC_I2C_SLAVE_ADDRESS 0x54

 /**
  * drm_scdc_read - read a block of data from SCDC
  * @adapter: I2C controller
  * @offset: start offset of block to read
  * @buffer: return location for the block to read
  * @size: size of the block to read
  *
  * Reads a block of data from SCDC, starting at a given offset.
  *
  * Returns:
  * 0 on success, negative error code on failure.
  */
 ssize_t drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer,
 		      size_t size)
 {
 	int ret;
 	struct i2c_msg msgs[2] = {
 		{
 			.addr = SCDC_I2C_SLAVE_ADDRESS,
 			.flags = 0,
 			.len = 1,
 			.buf = &offset,
 		}, {
 			.addr = SCDC_I2C_SLAVE_ADDRESS,
 			.flags = I2C_M_RD,
 			.len = size,
 			.buf = buffer,
 		}
 	};

 	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_scdc_read);

 /**
  * drm_scdc_write - write a block of data to SCDC
  * @adapter: I2C controller
  * @offset: start offset of block to write
  * @buffer: block of data to write
  * @size: size of the block to write
  *
  * Writes a block of data to SCDC, starting at a given offset.
  *
  * Returns:
  * 0 on success, negative error code on failure.
  */
 ssize_t drm_scdc_write(struct i2c_adapter *adapter, u8 offset,
 		       const void *buffer, size_t size)
 {
 	struct i2c_msg msg = {
 		.addr = SCDC_I2C_SLAVE_ADDRESS,
 		.flags = 0,
 		.len = 1 + size,
 		.buf = NULL,
 	};
 	void *data;
 	int err;

 	data = kmalloc(1 + size, GFP_TEMPORARY);
 	if (!data)
 		return -ENOMEM;

 	msg.buf = data;

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

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

 	kfree(data);

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

 	return 0;
 }
 EXPORT_SYMBOL(drm_scdc_write);

 /**
  * drm_scdc_check_scrambling_status - what is status of scrambling?
  * @adapter: I2C adapter for DDC channel
  *
  * Reads the scrambler status over SCDC, and checks the
  * scrambling status.
  *
  * Returns:
  * True if the scrambling is enabled, false otherwise.
  */

 bool drm_scdc_get_scrambling_status(struct i2c_adapter *adapter)
 {
 	u8 status;
 	int ret;

 	ret = drm_scdc_readb(adapter, SCDC_SCRAMBLER_STATUS, &status);
 	if (ret < 0) {
 		DRM_ERROR("Failed to read scrambling status, error %d\n", ret);
 		return false;
 	}

 	return status & SCDC_SCRAMBLING_STATUS;
 }
 EXPORT_SYMBOL(drm_scdc_get_scrambling_status);

 /**
  * drm_scdc_set_scrambling - enable scrambling
  * @adapter: I2C adapter for DDC channel
  * @enable: bool to indicate if scrambling is to be enabled/disabled
  *
  * Writes the TMDS config register over SCDC channel, and:
  * enables scrambling when enable = 1
  * disables scrambling when enable = 0
  *
  * Returns:
  * True if scrambling is set/reset successfully, false otherwise.
  */

 bool drm_scdc_set_scrambling(struct i2c_adapter *adapter, bool enable)
 {
 	u8 config;
 	int ret;

 	ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
 	if (ret < 0) {
 		DRM_ERROR("Failed to read tmds config, err=%d\n", ret);
 		return false;
 	}

 	if (enable)
 		config |= SCDC_SCRAMBLING_ENABLE;
 	else
 		config &= ~SCDC_SCRAMBLING_ENABLE;

 	ret = drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config);
 	if (ret < 0) {
 		DRM_ERROR("Failed to enable scrambling, error %d\n", ret);
 		return false;
 	}

 	return true;
 }
 EXPORT_SYMBOL(drm_scdc_set_scrambling);

 /**
  * drm_scdc_set_high_tmds_clock_ratio - set TMDS clock ratio
  * @adapter: I2C adapter for DDC channel
  * @set: ret or reset the high clock ratio
  *
  * TMDS clock ratio calculations go like this:
  * TMDS character = 10 bit TMDS encoded value
  * TMDS character rate = The rate at which TMDS characters are transmitted(Mcsc)
  * TMDS bit rate = 10x TMDS character rate
  * As per the spec:
  * TMDS clock rate for pixel clock < 340 MHz = 1x the character rate
  *	= 1/10 pixel clock rate
  * TMDS clock rate for pixel clock > 340 MHz = 0.25x the character rate
  *	= 1/40 pixel clock rate
  *
  * Writes to the TMDS config register over SCDC channel, and:
  * sets TMDS clock ratio to 1/40 when set = 1
  * sets TMDS clock ratio to 1/10 when set = 0
  *
  * Returns:
  * True if write is successful, false otherwise.
  */
 bool drm_scdc_set_high_tmds_clock_ratio(struct i2c_adapter *adapter, bool set)
 {
 	u8 config;
 	int ret;

 	ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
 	if (ret < 0) {
 		DRM_ERROR("Failed to read tmds config, err=%d\n", ret);
 		return false;
 	}

 	if (set)
 		config |= SCDC_TMDS_BIT_CLOCK_RATIO_BY_40;
 	else
 		config &= ~SCDC_TMDS_BIT_CLOCK_RATIO_BY_40;

 	ret = drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config);
 	if (ret < 0) {
 		DRM_ERROR("Failed to set TMDS clock ratio, error %d\n", ret);
 		return false;
 	}

 	/*
 	 * The spec says that a source should wait minimum 1ms and maximum
 	 * 100ms after writing the TMDS config for clock ratio. Lets allow a
 	 * wait of upto 2ms here.
 	 */
 	usleep_range(1000, 2000);
 	return true;
 }
 EXPORT_SYMBOL(drm_scdc_set_high_tmds_clock_ratio);
	/*
	* Copyright (c) 2015 NVIDIA Corporation. All rights reserved.
	*
	* 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, sub license,
	* 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 (including the
	* next paragraph) 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 NON-INFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS 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/slab.h>
	#include <linux/delay.h>

	#include <drm/drm_scdc_helper.h>
	#include <drm/drmP.h>

	/**
	* DOC: scdc helpers
	*
	* Status and Control Data Channel (SCDC) is a mechanism introduced by the
	* HDMI 2.0 specification. It is a point-to-point protocol that allows the
	* HDMI source and HDMI sink to exchange data. The same I2C interface that
	* is used to access EDID serves as the transport mechanism for SCDC.
	*/

	#define SCDC_I2C_SLAVE_ADDRESS 0x54

	/**
	* drm_scdc_read - read a block of data from SCDC
	* @adapter: I2C controller
	* @offset: start offset of block to read
	* @buffer: return location for the block to read
	* @size: size of the block to read
	*
	* Reads a block of data from SCDC, starting at a given offset.
	*
	* Returns:
	* 0 on success, negative error code on failure.
	*/
	ssize_t drm_scdc_read(struct i2c_adapter adapter, u8 offset, void buffer,
	size_t size)
	{
	int ret;
	struct i2c_msg msgs[2] = {
	{
	.addr = SCDC_I2C_SLAVE_ADDRESS,
	.flags = 0,
	.len = 1,
	.buf = &offset,
	}, {
	.addr = SCDC_I2C_SLAVE_ADDRESS,
	.flags = I2C_M_RD,
	.len = size,
	.buf = buffer,
	}
	};

	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_scdc_read);

	/**
	* drm_scdc_write - write a block of data to SCDC
	* @adapter: I2C controller
	* @offset: start offset of block to write
	* @buffer: block of data to write
	* @size: size of the block to write
	*
	* Writes a block of data to SCDC, starting at a given offset.
	*
	* Returns:
	* 0 on success, negative error code on failure.
	*/
	ssize_t drm_scdc_write(struct i2c_adapter *adapter, u8 offset,
	const void *buffer, size_t size)
	{
	struct i2c_msg msg = {
	.addr = SCDC_I2C_SLAVE_ADDRESS,
	.flags = 0,
	.len = 1 + size,
	.buf = NULL,
	};
	void *data;
	int err;

	data = kmalloc(1 + size, GFP_TEMPORARY);
	if (!data)
	return -ENOMEM;

	msg.buf = data;

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

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

	kfree(data);

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

	return 0;
	}
	EXPORT_SYMBOL(drm_scdc_write);

	/**
	* drm_scdc_check_scrambling_status - what is status of scrambling?
	* @adapter: I2C adapter for DDC channel
	*
	* Reads the scrambler status over SCDC, and checks the
	* scrambling status.
	*
	* Returns:
	* True if the scrambling is enabled, false otherwise.
	*/

	bool drm_scdc_get_scrambling_status(struct i2c_adapter *adapter)
	{
	u8 status;
	int ret;

	ret = drm_scdc_readb(adapter, SCDC_SCRAMBLER_STATUS, &status);
	if (ret < 0) {
	DRM_ERROR("Failed to read scrambling status, error %d\n", ret);
	return false;
	}

	return status & SCDC_SCRAMBLING_STATUS;
	}
	EXPORT_SYMBOL(drm_scdc_get_scrambling_status);

	/**
	* drm_scdc_set_scrambling - enable scrambling
	* @adapter: I2C adapter for DDC channel
	* @enable: bool to indicate if scrambling is to be enabled/disabled
	*
	* Writes the TMDS config register over SCDC channel, and:
	* enables scrambling when enable = 1
	* disables scrambling when enable = 0
	*
	* Returns:
	* True if scrambling is set/reset successfully, false otherwise.
	*/

	bool drm_scdc_set_scrambling(struct i2c_adapter *adapter, bool enable)
	{
	u8 config;
	int ret;

	ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
	if (ret < 0) {
	DRM_ERROR("Failed to read tmds config, err=%d\n", ret);
	return false;
	}

	if (enable)
	config \|= SCDC_SCRAMBLING_ENABLE;
	else
	config &= ~SCDC_SCRAMBLING_ENABLE;

	ret = drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config);
	if (ret < 0) {
	DRM_ERROR("Failed to enable scrambling, error %d\n", ret);
	return false;
	}

	return true;
	}
	EXPORT_SYMBOL(drm_scdc_set_scrambling);

	/**
	* drm_scdc_set_high_tmds_clock_ratio - set TMDS clock ratio
	* @adapter: I2C adapter for DDC channel
	* @set: ret or reset the high clock ratio
	*
	* TMDS clock ratio calculations go like this:
	* TMDS character = 10 bit TMDS encoded value
	* TMDS character rate = The rate at which TMDS characters are transmitted(Mcsc)
	* TMDS bit rate = 10x TMDS character rate
	* As per the spec:
	* TMDS clock rate for pixel clock < 340 MHz = 1x the character rate
	* = 1/10 pixel clock rate
	* TMDS clock rate for pixel clock > 340 MHz = 0.25x the character rate
	* = 1/40 pixel clock rate
	*
	* Writes to the TMDS config register over SCDC channel, and:
	* sets TMDS clock ratio to 1/40 when set = 1
	* sets TMDS clock ratio to 1/10 when set = 0
	*
	* Returns:
	* True if write is successful, false otherwise.
	*/
	bool drm_scdc_set_high_tmds_clock_ratio(struct i2c_adapter *adapter, bool set)
	{
	u8 config;
	int ret;

	ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
	if (ret < 0) {
	DRM_ERROR("Failed to read tmds config, err=%d\n", ret);
	return false;
	}

	if (set)
	config \|= SCDC_TMDS_BIT_CLOCK_RATIO_BY_40;
	else
	config &= ~SCDC_TMDS_BIT_CLOCK_RATIO_BY_40;

	ret = drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config);
	if (ret < 0) {
	DRM_ERROR("Failed to set TMDS clock ratio, error %d\n", ret);
	return false;
	}

	/*
	* The spec says that a source should wait minimum 1ms and maximum
	* 100ms after writing the TMDS config for clock ratio. Lets allow a
	* wait of upto 2ms here.
	*/
	usleep_range(1000, 2000);
	return true;
	}
	EXPORT_SYMBOL(drm_scdc_set_high_tmds_clock_ratio);