| Message ID | 1429340659-14369-5-git-send-email-tprevite@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat, Apr 18, 2015 at 12:04:18AM -0700, Todd Previte wrote: > For test 4.2.2.5 to pass per the Link CTS Core 1.2 rev1.1 spec, the source > device must attempt at least 7 times to read the EDID when it receives an > I2C defer. The normal DRM code makes only 7 retries, regardless of whether > or not the response is a native defer or an I2C defer. Test 4.2.2.5 fails > since there are native defers interspersed with the I2C defers which > results in less than 7 EDID read attempts. > > The solution is to add the numer of defers to the retry counter when an I2C > DEFER is returned such that another read attempt will be made. This situation > should normally only occur in compliance testing, however, as a worse case > real-world scenario, it would result in 13 attempts ( 6 native defers, 7 I2C > defers) for a single transaction to complete. The net result is a slightly > slower response to an EDID read that shouldn't significantly impact overall > performance. > > V2: > - Added a check on the number of I2C Defers to limit the number > of times that the retries variable will be decremented. This > is to address review feedback regarding possible infinite loops > from misbehaving sink devices. > V3: > - Fixed the limit value to 7 instead of 8 to get the correct retry > count. > - Combined the increment of the defer count into the if-statement > V4: > - Removed i915 tag from subject as the patch is not i915-specific > V5: > - Updated the for-loop to add the number of i2c defers to the retry > counter such that the correct number of retry attempts will be > made > > Signed-off-by: Todd Previte <tprevite@gmail.com> > Cc: dri-devel@lists.freedesktop.org > Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com> Applied to topic/drm-misc. -Daniel > --- > drivers/gpu/drm/drm_dp_helper.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c > index 575172e..80a02a4 100644 > --- a/drivers/gpu/drm/drm_dp_helper.c > +++ b/drivers/gpu/drm/drm_dp_helper.c > @@ -432,7 +432,7 @@ static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter) > */ > static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) > { > - unsigned int retry; > + unsigned int retry, defer_i2c; > int ret; > > /* > @@ -440,7 +440,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) > * is required to retry at least seven times upon receiving AUX_DEFER > * before giving up the AUX transaction. > */ > - for (retry = 0; retry < 7; retry++) { > + for (retry = 0, defer_i2c = 0; retry < (7 + defer_i2c); retry++) { > mutex_lock(&aux->hw_mutex); > ret = aux->transfer(aux, msg); > mutex_unlock(&aux->hw_mutex); > @@ -499,7 +499,13 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) > > case DP_AUX_I2C_REPLY_DEFER: > DRM_DEBUG_KMS("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 > + */ > aux->i2c_defer_count++; > + if (defer_i2c < 7) > + defer_i2c++; > usleep_range(400, 500); > continue; > > -- > 1.9.1 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/dri-devel
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 575172e..80a02a4 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -432,7 +432,7 @@ static u32 drm_dp_i2c_functionality(struct i2c_adapter *adapter) */ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) { - unsigned int retry; + unsigned int retry, defer_i2c; int ret; /* @@ -440,7 +440,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) * is required to retry at least seven times upon receiving AUX_DEFER * before giving up the AUX transaction. */ - for (retry = 0; retry < 7; retry++) { + for (retry = 0, defer_i2c = 0; retry < (7 + defer_i2c); retry++) { mutex_lock(&aux->hw_mutex); ret = aux->transfer(aux, msg); mutex_unlock(&aux->hw_mutex); @@ -499,7 +499,13 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) case DP_AUX_I2C_REPLY_DEFER: DRM_DEBUG_KMS("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 + */ aux->i2c_defer_count++; + if (defer_i2c < 7) + defer_i2c++; usleep_range(400, 500); continue;