From: Lyude <cpaul@redhat.com> To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: arthur.j.runyan@intel.com, "Ville Syrjälä" <ville.syrjala@linux.intel.com>, "Jani Nikula" <jani.nikula@linux.intel.com>, Lyude <cpaul@redhat.com>, "David Airlie" <airlied@linux.ie>, linux-kernel@vger.kernel.org (open list) Subject: [PATCH v4 4/5] drm/dp_helper: Perform throw-away read before actual read in drm_dp_dpcd_read() Date: Thu, 24 Mar 2016 14:27:09 -0400 [thread overview] Message-ID: <1458844031-2032-5-git-send-email-cpaul@redhat.com> (raw) In-Reply-To: <1458844031-2032-1-git-send-email-cpaul@redhat.com> This is part of a patch series to migrate all of the workarounds for commonly seen behavior from bad sinks in intel_dp_dpcd_read_wake() to drm's DP helper. Some sinks will just return garbage for the first aux tranaction they receive when coming out of sleep mode, so we need to perform an additional read before the actual read to workaround this. Signed-off-by: Lyude <cpaul@redhat.com> --- drivers/gpu/drm/drm_dp_helper.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 86656ca..702c78a 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -244,6 +244,13 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, void *buffer, size_t size) { + /* + * Sometimes we just get the same incorrect byte repeated over the + * entire buffer. Doing one throw away read initially seems to "solve" + * it. + */ + drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer, 1); + return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer, size); } -- 2.5.5
WARNING: multiple messages have this Message-ID (diff)
From: Lyude <cpaul@redhat.com> To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: arthur.j.runyan@intel.com, open list <linux-kernel@vger.kernel.org>, Lyude <cpaul@redhat.com> Subject: [PATCH v4 4/5] drm/dp_helper: Perform throw-away read before actual read in drm_dp_dpcd_read() Date: Thu, 24 Mar 2016 14:27:09 -0400 [thread overview] Message-ID: <1458844031-2032-5-git-send-email-cpaul@redhat.com> (raw) In-Reply-To: <1458844031-2032-1-git-send-email-cpaul@redhat.com> This is part of a patch series to migrate all of the workarounds for commonly seen behavior from bad sinks in intel_dp_dpcd_read_wake() to drm's DP helper. Some sinks will just return garbage for the first aux tranaction they receive when coming out of sleep mode, so we need to perform an additional read before the actual read to workaround this. Signed-off-by: Lyude <cpaul@redhat.com> --- drivers/gpu/drm/drm_dp_helper.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 86656ca..702c78a 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -244,6 +244,13 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request, ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, void *buffer, size_t size) { + /* + * Sometimes we just get the same incorrect byte repeated over the + * entire buffer. Doing one throw away read initially seems to "solve" + * it. + */ + drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer, 1); + return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer, size); } -- 2.5.5 _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2016-03-24 18:27 UTC|newest] Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-03-17 15:40 [PATCH 1/2] drm/dp_helper: retry on -ETIMEDOUT in drm_dp_dpcd_access() Lyude 2016-03-17 15:40 ` Lyude 2016-03-17 15:40 ` [PATCH 2/2] drm/i915: Get rid of intel_dp_dpcd_read_wake() Lyude 2016-03-17 15:40 ` Lyude 2016-03-17 17:56 ` Jani Nikula 2016-03-17 17:56 ` Jani Nikula 2016-03-18 15:57 ` [Intel-gfx] " Daniel Vetter 2016-03-18 15:57 ` Daniel Vetter 2016-03-18 14:13 ` Ville Syrjälä 2016-03-18 14:13 ` Ville Syrjälä 2016-03-18 16:12 ` [Intel-gfx] " Ville Syrjälä 2016-03-18 16:41 ` Ville Syrjälä 2016-03-18 16:41 ` Ville Syrjälä 2016-03-18 18:00 ` Daniel Vetter 2016-03-18 18:00 ` Daniel Vetter 2016-03-18 18:05 ` [Intel-gfx] " Ville Syrjälä 2016-03-21 16:37 ` Lyude Paul 2016-03-21 10:30 ` Jani Nikula 2016-03-21 10:30 ` Jani Nikula 2016-03-21 13:38 ` [Intel-gfx] " Ville Syrjälä 2016-03-21 13:38 ` Ville Syrjälä 2016-03-18 8:13 ` ✗ Fi.CI.BAT: failure for series starting with [1/2] drm/dp_helper: retry on -ETIMEDOUT in drm_dp_dpcd_access() Patchwork 2016-03-23 19:30 ` [PATCH v3 1/2] drm/dp_helper: add workarounds from intel_dp_dpcd_read_wake() Lyude 2016-03-23 19:30 ` Lyude 2016-03-23 19:33 ` [PATCH v3 1/2 RESEND] " Lyude 2016-03-23 19:33 ` Lyude 2016-03-24 9:37 ` Jani Nikula 2016-03-24 9:37 ` Jani Nikula 2016-03-24 18:27 ` [PATCH v4 0/5] Move workarounds from intel_dp_dpcd_read_wake() into drm's DP helpers Lyude 2016-03-24 18:27 ` Lyude 2016-03-24 18:27 ` [PATCH v4 1/5] drm/dp_helper: Increase retry interval to 1000us Lyude 2016-03-24 18:27 ` Lyude 2016-03-24 18:27 ` [PATCH v4 2/5] drm/dp_helper: Always wait before retrying native aux transactions Lyude 2016-03-24 18:27 ` Lyude 2016-03-24 18:27 ` [PATCH v4 3/5] drm/dp_helper: Retry aux transactions on all errors Lyude 2016-03-24 18:27 ` Lyude 2016-03-24 18:27 ` Lyude [this message] 2016-03-24 18:27 ` [PATCH v4 4/5] drm/dp_helper: Perform throw-away read before actual read in drm_dp_dpcd_read() Lyude 2016-03-24 18:27 ` [PATCH v4 5/5] drm/i915: Get rid of intel_dp_dpcd_read_wake() Lyude 2016-03-24 18:27 ` Lyude 2016-03-25 7:44 ` ✗ Fi.CI.BAT: failure for series starting with [v3,1/2,RESEND] drm/dp_helper: add workarounds from intel_dp_dpcd_read_wake() Patchwork
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