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linux/drivers/gpu/drm/drm_dp_helper.c

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/*
* Copyright © 2009 Keith Packard
*
* Permission to use, copy, modify, distribute, and sell this software and its
* documentation for any purpose is hereby granted without fee, provided that
* the above copyright notice appear in all copies and that both that copyright
* notice and this permission notice appear in supporting documentation, and
* that the name of the copyright holders not be used in advertising or
* publicity pertaining to distribution of the software without specific,
* written prior permission. The copyright holders make no representations
* about the suitability of this software for any purpose. It is provided "as
* is" without express or implied warranty.
*
* THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
* INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
* EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
* DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
* TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
* OF THIS SOFTWARE.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/i2c.h>
#include <drm/drm_dp_helper.h>
#include <drm/drmP.h>
/**
* DOC: dp helpers
*
* These functions contain some common logic and helpers at various abstraction
* levels to deal with Display Port sink devices and related things like DP aux
* channel transfers, EDID reading over DP aux channels, decoding certain DPCD
* blocks, ...
*/
/* Run a single AUX_CH I2C transaction, writing/reading data as necessary */
static int
i2c_algo_dp_aux_transaction(struct i2c_adapter *adapter, int mode,
uint8_t write_byte, uint8_t *read_byte)
{
struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
int ret;
ret = (*algo_data->aux_ch)(adapter, mode,
write_byte, read_byte);
return ret;
}
/*
* I2C over AUX CH
*/
/*
* Send the address. If the I2C link is running, this 'restarts'
* the connection with the new address, this is used for doing
* a write followed by a read (as needed for DDC)
*/
static int
i2c_algo_dp_aux_address(struct i2c_adapter *adapter, u16 address, bool reading)
{
struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
int mode = MODE_I2C_START;
int ret;
if (reading)
mode |= MODE_I2C_READ;
else
mode |= MODE_I2C_WRITE;
algo_data->address = address;
algo_data->running = true;
ret = i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
return ret;
}
/*
* Stop the I2C transaction. This closes out the link, sending
* a bare address packet with the MOT bit turned off
*/
static void
i2c_algo_dp_aux_stop(struct i2c_adapter *adapter, bool reading)
{
struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
int mode = MODE_I2C_STOP;
if (reading)
mode |= MODE_I2C_READ;
else
mode |= MODE_I2C_WRITE;
if (algo_data->running) {
(void) i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
algo_data->running = false;
}
}
/*
* Write a single byte to the current I2C address, the
* the I2C link must be running or this returns -EIO
*/
static int
i2c_algo_dp_aux_put_byte(struct i2c_adapter *adapter, u8 byte)
{
struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
int ret;
if (!algo_data->running)
return -EIO;
ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_WRITE, byte, NULL);
return ret;
}
/*
* Read a single byte from the current I2C address, the
* I2C link must be running or this returns -EIO
*/
static int
i2c_algo_dp_aux_get_byte(struct i2c_adapter *adapter, u8 *byte_ret)
{
struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
int ret;
if (!algo_data->running)
return -EIO;
ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_READ, 0, byte_ret);
return ret;
}
static int
i2c_algo_dp_aux_xfer(struct i2c_adapter *adapter,
struct i2c_msg *msgs,
int num)
{
int ret = 0;
bool reading = false;
int m;
int b;
for (m = 0; m < num; m++) {
u16 len = msgs[m].len;
u8 *buf = msgs[m].buf;
reading = (msgs[m].flags & I2C_M_RD) != 0;
ret = i2c_algo_dp_aux_address(adapter, msgs[m].addr, reading);
if (ret < 0)
break;
if (reading) {
for (b = 0; b < len; b++) {
ret = i2c_algo_dp_aux_get_byte(adapter, &buf[b]);
if (ret < 0)
break;
}
} else {
for (b = 0; b < len; b++) {
ret = i2c_algo_dp_aux_put_byte(adapter, buf[b]);
if (ret < 0)
break;
}
}
if (ret < 0)
break;
}
if (ret >= 0)
ret = num;
i2c_algo_dp_aux_stop(adapter, reading);
DRM_DEBUG_KMS("dp_aux_xfer return %d\n", ret);
return ret;
}
static u32
i2c_algo_dp_aux_functionality(struct i2c_adapter *adapter)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
I2C_FUNC_SMBUS_READ_BLOCK_DATA |
I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
I2C_FUNC_10BIT_ADDR;
}
static const struct i2c_algorithm i2c_dp_aux_algo = {
.master_xfer = i2c_algo_dp_aux_xfer,
.functionality = i2c_algo_dp_aux_functionality,
};
static void
i2c_dp_aux_reset_bus(struct i2c_adapter *adapter)
{
(void) i2c_algo_dp_aux_address(adapter, 0, false);
(void) i2c_algo_dp_aux_stop(adapter, false);
}
static int
i2c_dp_aux_prepare_bus(struct i2c_adapter *adapter)
{
adapter->algo = &i2c_dp_aux_algo;
adapter->retries = 3;
i2c_dp_aux_reset_bus(adapter);
return 0;
}
/**
* i2c_dp_aux_add_bus() - register an i2c adapter using the aux ch helper
* @adapter: i2c adapter to register
*
* This registers an i2c adapater that uses dp aux channel as it's underlaying
* transport. The driver needs to fill out the &i2c_algo_dp_aux_data structure
* and store it in the algo_data member of the @adapter argument. This will be
* used by the i2c over dp aux algorithm to drive the hardware.
*
* RETURNS:
* 0 on success, -ERRNO on failure.
*/
int
i2c_dp_aux_add_bus(struct i2c_adapter *adapter)
{
int error;
error = i2c_dp_aux_prepare_bus(adapter);
if (error)
return error;
error = i2c_add_adapter(adapter);
return error;
}
EXPORT_SYMBOL(i2c_dp_aux_add_bus);
/* Helpers for DP link training */
static u8 dp_link_status(const u8 link_status[DP_LINK_STATUS_SIZE], int r)
{
return link_status[r - DP_LANE0_1_STATUS];
}
static u8 dp_get_lane_status(const u8 link_status[DP_LINK_STATUS_SIZE],
int lane)
{
int i = DP_LANE0_1_STATUS + (lane >> 1);
int s = (lane & 1) * 4;
u8 l = dp_link_status(link_status, i);
return (l >> s) & 0xf;
}
bool drm_dp_channel_eq_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
int lane_count)
{
u8 lane_align;
u8 lane_status;
int lane;
lane_align = dp_link_status(link_status,
DP_LANE_ALIGN_STATUS_UPDATED);
if ((lane_align & DP_INTERLANE_ALIGN_DONE) == 0)
return false;
for (lane = 0; lane < lane_count; lane++) {
lane_status = dp_get_lane_status(link_status, lane);
if ((lane_status & DP_CHANNEL_EQ_BITS) != DP_CHANNEL_EQ_BITS)
return false;
}
return true;
}
EXPORT_SYMBOL(drm_dp_channel_eq_ok);
bool drm_dp_clock_recovery_ok(const u8 link_status[DP_LINK_STATUS_SIZE],
int lane_count)
{
int lane;
u8 lane_status;
for (lane = 0; lane < lane_count; lane++) {
lane_status = dp_get_lane_status(link_status, lane);
if ((lane_status & DP_LANE_CR_DONE) == 0)
return false;
}
return true;
}
EXPORT_SYMBOL(drm_dp_clock_recovery_ok);
u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE],
int lane)
{
int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
int s = ((lane & 1) ?
DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT :
DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT);
u8 l = dp_link_status(link_status, i);
return ((l >> s) & 0x3) << DP_TRAIN_VOLTAGE_SWING_SHIFT;
}
EXPORT_SYMBOL(drm_dp_get_adjust_request_voltage);
u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE],
int lane)
{
int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
int s = ((lane & 1) ?
DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT :
DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT);
u8 l = dp_link_status(link_status, i);
return ((l >> s) & 0x3) << DP_TRAIN_PRE_EMPHASIS_SHIFT;
}
EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);
void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
udelay(100);
else
mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
}
EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);
void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
udelay(400);
else
mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
}
EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);
u8 drm_dp_link_rate_to_bw_code(int link_rate)
{
switch (link_rate) {
case 162000:
default:
return DP_LINK_BW_1_62;
case 270000:
return DP_LINK_BW_2_7;
case 540000:
return DP_LINK_BW_5_4;
}
}
EXPORT_SYMBOL(drm_dp_link_rate_to_bw_code);
int drm_dp_bw_code_to_link_rate(u8 link_bw)
{
switch (link_bw) {
case DP_LINK_BW_1_62:
default:
return 162000;
case DP_LINK_BW_2_7:
return 270000;
case DP_LINK_BW_5_4:
return 540000;
}
}
EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);
/**
* DOC: dp helpers
*
* The DisplayPort AUX channel is an abstraction to allow generic, driver-
* independent access to AUX functionality. Drivers can take advantage of
* this by filling in the fields of the drm_dp_aux structure.
*
* Transactions are described using a hardware-independent drm_dp_aux_msg
* structure, which is passed into a driver's .transfer() implementation.
* Both native and I2C-over-AUX transactions are supported.
*/
static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
unsigned int offset, void *buffer, size_t size)
{
struct drm_dp_aux_msg msg;
unsigned int retry;
int err;
memset(&msg, 0, sizeof(msg));
msg.address = offset;
msg.request = request;
msg.buffer = buffer;
msg.size = size;
/*
* The specification doesn't give any recommendation on how often to
* retry native transactions, so retry 7 times like for I2C-over-AUX
* transactions.
*/
for (retry = 0; retry < 7; retry++) {
err = aux->transfer(aux, &msg);
if (err < 0) {
if (err == -EBUSY)
continue;
return err;
}
if (err < size)
return -EPROTO;
switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) {
case DP_AUX_NATIVE_REPLY_ACK:
return err;
case DP_AUX_NATIVE_REPLY_NACK:
return -EIO;
case DP_AUX_NATIVE_REPLY_DEFER:
usleep_range(400, 500);
break;
}
}
DRM_ERROR("too many retries, giving up\n");
return -EIO;
}
/**
* drm_dp_dpcd_read() - read a series of bytes from the DPCD
* @aux: DisplayPort AUX channel
* @offset: address of the (first) register to read
* @buffer: buffer to store the register values
* @size: number of bytes in @buffer
*
* Returns the number of bytes transferred on success, or a negative error
* code on failure. -EIO is returned if the request was NAKed by the sink or
* if the retry count was exceeded. If not all bytes were transferred, this
* function returns -EPROTO. Errors from the underlying AUX channel transfer
* function, with the exception of -EBUSY (which causes the transaction to
* be retried), are propagated to the caller.
*/
ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
void *buffer, size_t size)
{
return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
size);
}
EXPORT_SYMBOL(drm_dp_dpcd_read);
/**
* drm_dp_dpcd_write() - write a series of bytes to the DPCD
* @aux: DisplayPort AUX channel
* @offset: address of the (first) register to write
* @buffer: buffer containing the values to write
* @size: number of bytes in @buffer
*
* Returns the number of bytes transferred on success, or a negative error
* code on failure. -EIO is returned if the request was NAKed by the sink or
* if the retry count was exceeded. If not all bytes were transferred, this
* function returns -EPROTO. Errors from the underlying AUX channel transfer
* function, with the exception of -EBUSY (which causes the transaction to
* be retried), are propagated to the caller.
*/
ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
void *buffer, size_t size)
{
return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
size);
}
EXPORT_SYMBOL(drm_dp_dpcd_write);
/**
* drm_dp_dpcd_read_link_status() - read DPCD link status (bytes 0x202-0x207)
* @aux: DisplayPort AUX channel
* @status: buffer to store the link status in (must be at least 6 bytes)
*
* Returns the number of bytes transferred on success or a negative error
* code on failure.
*/
int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
u8 status[DP_LINK_STATUS_SIZE])
{
return drm_dp_dpcd_read(aux, DP_LANE0_1_STATUS, status,
DP_LINK_STATUS_SIZE);
}
EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
/**
* drm_dp_link_probe() - probe a DisplayPort link for capabilities
* @aux: DisplayPort AUX channel
* @link: pointer to structure in which to return link capabilities
*
* The structure filled in by this function can usually be passed directly
* into drm_dp_link_power_up() and drm_dp_link_configure() to power up and
* configure the link based on the link's capabilities.
*
* Returns 0 on success or a negative error code on failure.
*/
int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link)
{
u8 values[3];
int err;
memset(link, 0, sizeof(*link));
err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values));
if (err < 0)
return err;
link->revision = values[0];
link->rate = drm_dp_bw_code_to_link_rate(values[1]);
link->num_lanes = values[2] & DP_MAX_LANE_COUNT_MASK;
if (values[2] & DP_ENHANCED_FRAME_CAP)
link->capabilities |= DP_LINK_CAP_ENHANCED_FRAMING;
return 0;
}
EXPORT_SYMBOL(drm_dp_link_probe);
/**
* drm_dp_link_power_up() - power up a DisplayPort link
* @aux: DisplayPort AUX channel
* @link: pointer to a structure containing the link configuration
*
* Returns 0 on success or a negative error code on failure.
*/
int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link)
{
u8 value;
int err;
/* DP_SET_POWER register is only available on DPCD v1.1 and later */
if (link->revision < 0x11)
return 0;
err = drm_dp_dpcd_readb(aux, DP_SET_POWER, &value);
if (err < 0)
return err;
value &= ~DP_SET_POWER_MASK;
value |= DP_SET_POWER_D0;
err = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
if (err < 0)
return err;
/*
* According to the DP 1.1 specification, a "Sink Device must exit the
* power saving state within 1 ms" (Section 2.5.3.1, Table 5-52, "Sink
* Control Field" (register 0x600).
*/
usleep_range(1000, 2000);
return 0;
}
EXPORT_SYMBOL(drm_dp_link_power_up);
/**
* drm_dp_link_configure() - configure a DisplayPort link
* @aux: DisplayPort AUX channel
* @link: pointer to a structure containing the link configuration
*
* Returns 0 on success or a negative error code on failure.
*/
int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link)
{
u8 values[2];
int err;
values[0] = drm_dp_link_rate_to_bw_code(link->rate);
values[1] = link->num_lanes;
if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING)
values[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN;
err = drm_dp_dpcd_write(aux, DP_LINK_BW_SET, values, sizeof(values));
if (err < 0)
return err;
return 0;
}
EXPORT_SYMBOL(drm_dp_link_configure);
/*
* I2C-over-AUX implementation
*/
static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
I2C_FUNC_SMBUS_READ_BLOCK_DATA |
I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
I2C_FUNC_10BIT_ADDR;
}
/*
* Transfer a single I2C-over-AUX message and handle various error conditions,
* retrying the transaction as appropriate.
*/
static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
{
unsigned int retry;
int err;
/*
* DP1.2 sections 2.7.7.1.5.6.1 and 2.7.7.1.6.6.1: A DP Source device
* is required to retry at least seven times upon receiving AUX_DEFER
* before giving up the AUX transaction.
*/
for (retry = 0; retry < 7; retry++) {
err = aux->transfer(aux, msg);
if (err < 0) {
if (err == -EBUSY)
continue;
DRM_DEBUG_KMS("transaction failed: %d\n", err);
return err;
}
if (err < msg->size)
return -EPROTO;
switch (msg->reply & DP_AUX_NATIVE_REPLY_MASK) {
case DP_AUX_NATIVE_REPLY_ACK:
/*
* For I2C-over-AUX transactions this isn't enough, we
* need to check for the I2C ACK reply.
*/
break;
case DP_AUX_NATIVE_REPLY_NACK:
DRM_DEBUG_KMS("native nack\n");
return -EREMOTEIO;
case DP_AUX_NATIVE_REPLY_DEFER:
DRM_DEBUG_KMS("native defer");
/*
* We could check for I2C bit rate capabilities and if
* available adjust this interval. We could also be
* more careful with DP-to-legacy adapters where a
* long legacy cable may force very low I2C bit rates.
*
* For now just defer for long enough to hopefully be
* safe for all use-cases.
*/
usleep_range(500, 600);
continue;
default:
DRM_ERROR("invalid native reply %#04x\n", msg->reply);
return -EREMOTEIO;
}
switch (msg->reply & DP_AUX_I2C_REPLY_MASK) {
case DP_AUX_I2C_REPLY_ACK:
/*
* Both native ACK and I2C ACK replies received. We
* can assume the transfer was successful.
*/
return 0;
case DP_AUX_I2C_REPLY_NACK:
DRM_DEBUG_KMS("I2C nack\n");
return -EREMOTEIO;
case DP_AUX_I2C_REPLY_DEFER:
DRM_DEBUG_KMS("I2C defer\n");
usleep_range(400, 500);
continue;
default:
DRM_ERROR("invalid I2C reply %#04x\n", msg->reply);
return -EREMOTEIO;
}
}
DRM_ERROR("too many retries, giving up\n");
return -EREMOTEIO;
}
static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
int num)
{
struct drm_dp_aux *aux = adapter->algo_data;
unsigned int i, j;
for (i = 0; i < num; i++) {
struct drm_dp_aux_msg msg;
int err;
/*
* Many hardware implementations support FIFOs larger than a
* single byte, but it has been empirically determined that
* transferring data in larger chunks can actually lead to
* decreased performance. Therefore each message is simply
* transferred byte-by-byte.
*/
for (j = 0; j < msgs[i].len; j++) {
memset(&msg, 0, sizeof(msg));
msg.address = msgs[i].addr;
msg.request = (msgs[i].flags & I2C_M_RD) ?
DP_AUX_I2C_READ :
DP_AUX_I2C_WRITE;
/*
* All messages except the last one are middle-of-
* transfer messages.
*/
if ((i < num - 1) || (j < msgs[i].len - 1))
msg.request |= DP_AUX_I2C_MOT;
msg.buffer = msgs[i].buf + j;
msg.size = 1;
err = drm_dp_i2c_do_msg(aux, &msg);
if (err < 0)
return err;
}
}
return num;
}
static const struct i2c_algorithm drm_dp_i2c_algo = {
.functionality = drm_dp_i2c_functionality,
.master_xfer = drm_dp_i2c_xfer,
};
/**
* drm_dp_aux_register_i2c_bus() - register an I2C adapter for I2C-over-AUX
* @aux: DisplayPort AUX channel
*
* Returns 0 on success or a negative error code on failure.
*/
int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux)
{
aux->ddc.algo = &drm_dp_i2c_algo;
aux->ddc.algo_data = aux;
aux->ddc.retries = 3;
aux->ddc.class = I2C_CLASS_DDC;
aux->ddc.owner = THIS_MODULE;
aux->ddc.dev.parent = aux->dev;
aux->ddc.dev.of_node = aux->dev->of_node;
strncpy(aux->ddc.name, dev_name(aux->dev), sizeof(aux->ddc.name));
return i2c_add_adapter(&aux->ddc);
}
EXPORT_SYMBOL(drm_dp_aux_register_i2c_bus);
/**
* drm_dp_aux_unregister_i2c_bus() - unregister an I2C-over-AUX adapter
* @aux: DisplayPort AUX channel
*/
void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux)
{
i2c_del_adapter(&aux->ddc);
}
EXPORT_SYMBOL(drm_dp_aux_unregister_i2c_bus);
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