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drm: DisplayPort AUX framework for v3.15-rc1 

This series of patches implements a small framework that abstracts away
 some of the functionality that the DisplayPort AUX channel provides. It
 comes with a set of generic helpers that use the driver implementations
 to reduce code duplication.
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Merge tag 'drm/dp-aux-for-3.15-rc1' of git://anongit.freedesktop.org/tegra/linux into drm-next

drm: DisplayPort AUX framework for v3.15-rc1

This series of patches implements a small framework that abstracts away
some of the functionality that the DisplayPort AUX channel provides. It
comes with a set of generic helpers that use the driver implementations
to reduce code duplication.

* tag 'drm/dp-aux-for-3.15-rc1' of git://anongit.freedesktop.org/tegra/linux:
  drm/dp: Allow registering AUX channels as I2C busses
  drm/dp: Add DisplayPort link helpers
  drm/dp: Add drm_dp_dpcd_read_link_status()
  drm/dp: Add AUX channel infrastructure
This commit is contained in:
Dave Airlie 2014-02-27 14:30:08 +10:00
parent cfbf8d4857 88759686c7
commit 6ba6b7cdaf
2 changed files with 506 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

395
drivers/gpu/drm/drm_dp_helper.c
View File

@ -346,3 +346,398 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw)
}
}
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);

111
include/drm/drm_dp_helper.h
View File

@ -291,6 +291,7 @@
#define DP_SET_POWER 0x600
# define DP_SET_POWER_D0 0x1
# define DP_SET_POWER_D3 0x2
# define DP_SET_POWER_MASK 0x3
#define DP_PSR_ERROR_STATUS 0x2006 /* XXX 1.2? */
# define DP_PSR_LINK_CRC_ERROR (1 << 0)
@ -398,4 +399,114 @@ drm_dp_enhanced_frame_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
(dpcd[DP_MAX_LANE_COUNT] & DP_ENHANCED_FRAME_CAP);
}
/*
* DisplayPort AUX channel
*/
/**
* struct drm_dp_aux_msg - DisplayPort AUX channel transaction
* @address: address of the (first) register to access
* @request: contains the type of transaction (see DP_AUX_* macros)
* @reply: upon completion, contains the reply type of the transaction
* @buffer: pointer to a transmission or reception buffer
* @size: size of @buffer
*/
struct drm_dp_aux_msg {
unsigned int address;
u8 request;
u8 reply;
void *buffer;
size_t size;
};
/**
* struct drm_dp_aux - DisplayPort AUX channel
* @ddc: I2C adapter that can be used for I2C-over-AUX communication
* @dev: pointer to struct device that is the parent for this AUX channel
* @transfer: transfers a message representing a single AUX transaction
*
* The .dev field should be set to a pointer to the device that implements
* the AUX channel.
*
* Drivers provide a hardware-specific implementation of how transactions
* are executed via the .transfer() function. A pointer to a drm_dp_aux_msg
* structure describing the transaction is passed into this function. Upon
* success, the implementation should return the number of payload bytes
* that were transferred, or a negative error-code on failure. Helpers
* propagate errors from the .transfer() function, with the exception of
* the -EBUSY error, which causes a transaction to be retried. On a short,
* helpers will return -EPROTO to make it simpler to check for failure.
*
* An AUX channel can also be used to transport I2C messages to a sink. A
* typical application of that is to access an EDID that's present in the
* sink device. The .transfer() function can also be used to execute such
* transactions. The drm_dp_aux_register_i2c_bus() function registers an
* I2C adapter that can be passed to drm_probe_ddc(). Upon removal, drivers
* should call drm_dp_aux_unregister_i2c_bus() to remove the I2C adapter.
*/
struct drm_dp_aux {
struct i2c_adapter ddc;
struct device *dev;
ssize_t (*transfer)(struct drm_dp_aux *aux,
struct drm_dp_aux_msg *msg);
};
ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
void *buffer, size_t size);
ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
void *buffer, size_t size);
/**
* drm_dp_dpcd_readb() - read a single byte from the DPCD
* @aux: DisplayPort AUX channel
* @offset: address of the register to read
* @valuep: location where the value of the register will be stored
*
* Returns the number of bytes transferred (1) on success, or a negative
* error code on failure.
*/
static inline ssize_t drm_dp_dpcd_readb(struct drm_dp_aux *aux,
unsigned int offset, u8 *valuep)
{
return drm_dp_dpcd_read(aux, offset, valuep, 1);
}
/**
* drm_dp_dpcd_writeb() - write a single byte to the DPCD
* @aux: DisplayPort AUX channel
* @offset: address of the register to write
* @value: value to write to the register
*
* Returns the number of bytes transferred (1) on success, or a negative
* error code on failure.
*/
static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux,
unsigned int offset, u8 value)
{
return drm_dp_dpcd_write(aux, offset, &value, 1);
}
int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
u8 status[DP_LINK_STATUS_SIZE]);
/*
* DisplayPort link
*/
#define DP_LINK_CAP_ENHANCED_FRAMING (1 << 0)
struct drm_dp_link {
unsigned char revision;
unsigned int rate;
unsigned int num_lanes;
unsigned long capabilities;
};
int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link);
int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link);
int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);
int drm_dp_aux_register_i2c_bus(struct drm_dp_aux *aux);
void drm_dp_aux_unregister_i2c_bus(struct drm_dp_aux *aux);
#endif /* _DRM_DP_HELPER_H_ */