Add a new drm_debug bit for turning on DPCD logging, to aid debugging with troublesome monitors.

v2: don't try to hexdump the universe if driver returns -errno, and change the "too many retries" traces to DRM_ERROR()

Signed-off-by: Rob Clark robdclark@gmail.com --- drivers/gpu/drm/drm_dp_helper.c | 60 ++++++++++++++++++++++++++++++++++------- include/drm/drmP.h | 10 ++++++- 2 files changed, 59 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 76e08dc..3f27cc9 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -159,6 +159,44 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw) } EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);

+static ssize_t aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) +{ + ssize_t ret; + + DRM_DEBUG_DPCD("%s: req=0x%02x, address=0x%05x, size=%zu\n", aux->name, + msg->request, msg->address, msg->size); + + if (unlikely(drm_debug & DRM_UT_DPCD)) { + switch (msg->request & ~DP_AUX_I2C_MOT) { + case DP_AUX_NATIVE_WRITE: + case DP_AUX_I2C_WRITE: + print_hex_dump(KERN_DEBUG, "DPCD: ", DUMP_PREFIX_OFFSET, + 16, 1, msg->buffer, msg->size, false); + break; + default: + break; + } + } + + ret = aux->transfer(aux, msg); + + DRM_DEBUG_DPCD("%s: reply=0x%02x, size=%zd\n", aux->name, msg->reply, ret); + + if (unlikely(drm_debug & DRM_UT_DPCD) && (ret > 0)) { + switch (msg->request & ~DP_AUX_I2C_MOT) { + case DP_AUX_NATIVE_READ: + case DP_AUX_I2C_READ: + print_hex_dump(KERN_DEBUG, "DPCD: ", DUMP_PREFIX_OFFSET, + 16, 1, msg->buffer, ret, false); + break; + default: + break; + } + } + + return ret; +} + #define AUX_RETRY_INTERVAL 500 /* us */

/** @@ -196,7 +234,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, */ for (retry = 0; retry < 32; retry++) {

- err = aux->transfer(aux, &msg); + err = aux_transfer(aux, &msg); if (err < 0) { if (err == -EBUSY) continue; @@ -212,16 +250,18 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, goto unlock;

case DP_AUX_NATIVE_REPLY_NACK: + DRM_DEBUG_DPCD("native nack (result=%d, size=%zu)\n", err, msg.size); err = -EIO; goto unlock;

case DP_AUX_NATIVE_REPLY_DEFER: + DRM_DEBUG_DPCD("native defer\n"); usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100); break; } }

- DRM_DEBUG_KMS("too many retries, giving up\n"); + DRM_ERROR("DPCD: too many retries, giving up!\n"); err = -EIO;

unlock: @@ -550,12 +590,12 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) WARN_ON(!mutex_is_locked(&aux->hw_mutex));

for (retry = 0, defer_i2c = 0; retry < (max_retries + defer_i2c); retry++) { - ret = aux->transfer(aux, msg); + ret = aux_transfer(aux, msg); if (ret < 0) { if (ret == -EBUSY) continue;

- DRM_DEBUG_KMS("transaction failed: %d\n", ret); + DRM_DEBUG_DPCD("transaction failed: %d\n", ret); return ret; }

@@ -569,11 +609,11 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) break;

case DP_AUX_NATIVE_REPLY_NACK: - DRM_DEBUG_KMS("native nack (result=%d, size=%zu)\n", ret, msg->size); + DRM_DEBUG_DPCD("native nack (result=%d, size=%zu)\n", ret, msg->size); return -EREMOTEIO;

case DP_AUX_NATIVE_REPLY_DEFER: - DRM_DEBUG_KMS("native defer\n"); + DRM_DEBUG_DPCD("native defer\n"); /* * We could check for I2C bit rate capabilities and if * available adjust this interval. We could also be @@ -602,12 +642,12 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) return ret;

case DP_AUX_I2C_REPLY_NACK: - DRM_DEBUG_KMS("I2C nack (result=%d, size=%zu\n", ret, msg->size); + DRM_DEBUG_DPCD("I2C nack (result=%d, size=%zu\n", ret, msg->size); aux->i2c_nack_count++; return -EREMOTEIO;

case DP_AUX_I2C_REPLY_DEFER: - DRM_DEBUG_KMS("I2C defer\n"); + DRM_DEBUG_DPCD("I2C defer\n"); /* DP Compliance Test 4.2.2.5 Requirement: * Must have at least 7 retries for I2C defers on the * transaction to pass this test @@ -626,7 +666,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) } }

- DRM_DEBUG_KMS("too many retries, giving up\n"); + DRM_ERROR("I2C: too many retries, giving up\n"); return -EREMOTEIO; }

@@ -654,7 +694,7 @@ static int drm_dp_i2c_drain_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *o return err == 0 ? -EPROTO : err;

if (err < msg.size && err < ret) { - DRM_DEBUG_KMS("Partial I2C reply: requested %zu bytes got %d bytes\n", + DRM_DEBUG_DPCD("Partial I2C reply: requested %zu bytes got %d bytes\n", msg.size, err); ret = err; } diff --git a/include/drm/drmP.h b/include/drm/drmP.h index 0a271ca..ac4d622 100644 --- a/include/drm/drmP.h +++ b/include/drm/drmP.h @@ -110,6 +110,8 @@ struct dma_buf_attachment; * VBL: used for verbose debug message in the vblank code * This is the category used by the DRM_DEBUG_VBL() macro. * + * DPCD: used to log (displayport) DPCD messages + * * Enabling verbose debug messages is done through the drm.debug parameter, * each category being enabled by a bit. * @@ -117,7 +119,7 @@ struct dma_buf_attachment; * drm.debug=0x2 will enable DRIVER messages * drm.debug=0x3 will enable CORE and DRIVER messages * ... - * drm.debug=0x3f will enable all messages + * drm.debug=0x7f will enable all messages * * An interesting feature is that it's possible to enable verbose logging at * run-time by echoing the debug value in its sysfs node: @@ -129,6 +131,7 @@ struct dma_buf_attachment; #define DRM_UT_PRIME 0x08 #define DRM_UT_ATOMIC 0x10 #define DRM_UT_VBL 0x20 +#define DRM_UT_DPCD 0x40

extern __printf(2, 3) void drm_ut_debug_printk(const char *function_name, @@ -226,6 +229,11 @@ void drm_err(const char *format, ...); if (unlikely(drm_debug & DRM_UT_VBL)) \ drm_ut_debug_printk(__func__, fmt, ##args); \ } while (0) +#define DRM_DEBUG_DPCD(fmt, args...) \ + do { \ + if (unlikely(drm_debug & DRM_UT_DPCD)) \ + drm_ut_debug_printk(__func__, fmt, ##args); \ + } while (0)

/*@}*/

On Wed, Dec 09, 2015 at 04:20:09PM -0500, Rob Clark wrote:

Something small missing here perhaps. The patch subject is not part of the commit message body.

1. don't let other threads trying to bang on aux channel interrupt the

defer timeout/logic 2) don't let other threads interrupt the i2c over aux logic

Technically, according to people who actually have the DP spec, this should not be required. In practice, it makes some troublesome Dell monitor (and perhaps others) work, so probably a case of "It's compliant if it works with windows" on the hw vendor's part..

Reported-by: Dave Wysochanski dwysocha@redhat.com Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1274157 Cc: stable@vger.kernel.org Signed-off-by: Rob Clark robdclark@gmail.com

Real world wins.

Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com

---

drivers/gpu/drm/drm_dp_helper.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 9535c5b..76e08dc 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -178,7 +178,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, { struct drm_dp_aux_msg msg; unsigned int retry;

• int err;

• int err = 0;

  memset(&msg, 0, sizeof(msg)); msg.address = offset;

@@ -186,6 +186,8 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, msg.buffer = buffer; msg.size = size;

• mutex_lock(&aux->hw_mutex);
• /*
  • The specification doesn't give any recommendation on how often to
  • retry native transactions. We used to retry 7 times like for

@@ -194,25 +196,24 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, */ for (retry = 0; retry < 32; retry++) {

• mutex_lock(&aux->hw_mutex);
  

  err = aux->transfer(aux, &msg);

• mutex_unlock(&aux->hw_mutex);
  

  if (err < 0) { if (err == -EBUSY) continue;

• 	return err;
  

• 	goto unlock;
  

  }

  switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) { case DP_AUX_NATIVE_REPLY_ACK: if (err < size)

• 		return -EPROTO;
  

• 	return err;
  

• 		err = -EPROTO;
  

• 	goto unlock;
  
  

  case DP_AUX_NATIVE_REPLY_NACK:

• 	return -EIO;
  

• 	err = -EIO;
  

• 	goto unlock;
  
  

  case DP_AUX_NATIVE_REPLY_DEFER: usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);

@@ -221,7 +222,11 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, }

DRM_DEBUG_KMS("too many retries, giving up\n");

• return -EIO;

• err = -EIO;

+unlock:

• mutex_unlock(&aux->hw_mutex);
• return err;

}

/** @@ -542,10 +547,10 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) */ int max_retries = max(7, drm_dp_i2c_retry_count(msg, dp_aux_i2c_speed_khz));

• WARN_ON(!mutex_is_locked(&aux->hw_mutex));
• for (retry = 0, defer_i2c = 0; retry < (max_retries + defer_i2c); retry++) {

• mutex_lock(&aux->hw_mutex);
  

  ret = aux->transfer(aux, msg);

• mutex_unlock(&aux->hw_mutex);
  

  if (ret < 0) { if (ret == -EBUSY) continue;

@@ -684,6 +689,8 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,

memset(&msg, 0, sizeof(msg));

• mutex_lock(&aux->hw_mutex);
• for (i = 0; i < num; i++) { msg.address = msgs[i].addr; drm_dp_i2c_msg_set_request(&msg, &msgs[i]);

@@ -738,6 +745,8 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, msg.size = 0; (void)drm_dp_i2c_do_msg(aux, &msg);

• mutex_unlock(&aux->hw_mutex);
• return err;

}

-- 2.5.0

---

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