/*
* 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_print.h>
#include <drm/drm_scdc_helper.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_KERNEL);
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_get_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_DEBUG_KMS("Failed to read scrambling status: %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_DEBUG_KMS("Failed to read TMDS config: %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_DEBUG_KMS("Failed to enable scrambling: %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_DEBUG_KMS("Failed to read TMDS config: %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_DEBUG_KMS("Failed to set TMDS clock ratio: %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 up to 2ms here.
*/
usleep_range(1000, 2000);
return true;
}
EXPORT_SYMBOL(drm_scdc_set_high_tmds_clock_ratio);
