From: Lyude <cpaul@redhat.com> To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, "Jani Nikula" <jani.nikula@linux.intel.com>, "Ville Syrjälä" <ville.syrjala@linux.intel.com> Cc: Lyude <cpaul@redhat.com>, David Airlie <airlied@linux.ie>, linux-kernel@vger.kernel.org (open list) Subject: [PATCH v5 3/4] drm/dp_helper: Perform throw-away read before actual read in drm_dp_dpcd_read() Date: Wed, 13 Apr 2016 10:58:32 -0400 [thread overview] Message-ID: <1460559513-32280-4-git-send-email-cpaul@redhat.com> (raw) In-Reply-To: <1460559513-32280-1-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. Changes since v5 - If the throwaway read in drm_dp_dpcd_read() fails, return the error from that instead of continuing. This follows the same logic we do in drm_dp_dpcd_access() (e.g. the error from the first transaction may differ from the errors that proceeding attempts might return). Signed-off-by: Lyude <cpaul@redhat.com> --- drivers/gpu/drm/drm_dp_helper.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 540c3e4..aa80702 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -248,6 +248,18 @@ unlock: ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, void *buffer, size_t size) { + int ret; + + /* + * Sometimes we just get the same incorrect byte repeated over the + * entire buffer. Doing one throw away read initially seems to "solve" + * it. + */ + ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer, + 1); + if (ret != 1) + return ret; + 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, "Jani Nikula" <jani.nikula@linux.intel.com>, "Ville Syrjälä" <ville.syrjala@linux.intel.com> Cc: David Airlie <airlied@linux.ie>, open list <linux-kernel@vger.kernel.org> Subject: [PATCH v5 3/4] drm/dp_helper: Perform throw-away read before actual read in drm_dp_dpcd_read() Date: Wed, 13 Apr 2016 10:58:32 -0400 [thread overview] Message-ID: <1460559513-32280-4-git-send-email-cpaul@redhat.com> (raw) In-Reply-To: <1460559513-32280-1-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. Changes since v5 - If the throwaway read in drm_dp_dpcd_read() fails, return the error from that instead of continuing. This follows the same logic we do in drm_dp_dpcd_access() (e.g. the error from the first transaction may differ from the errors that proceeding attempts might return). Signed-off-by: Lyude <cpaul@redhat.com> --- drivers/gpu/drm/drm_dp_helper.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 540c3e4..aa80702 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -248,6 +248,18 @@ unlock: ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, void *buffer, size_t size) { + int ret; + + /* + * Sometimes we just get the same incorrect byte repeated over the + * entire buffer. Doing one throw away read initially seems to "solve" + * it. + */ + ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer, + 1); + if (ret != 1) + return ret; + return drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer, size); } -- 2.5.5 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
next prev parent reply other threads:[~2016-04-13 14:59 UTC|newest] Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-03-28 14:33 [PATCH v4 RESEND 0/5] Move workarounds from intel_dp_dpcd_read_wake() into drm's DP helpers Lyude 2016-03-28 14:33 ` Lyude 2016-03-28 14:31 ` ✗ Fi.CI.BAT: failure for " Patchwork 2016-03-28 14:33 ` [PATCH v4 RESEND 1/5] drm/dp_helper: Increase retry interval to 1000us Lyude 2016-03-28 14:33 ` Lyude 2016-03-29 8:27 ` Daniel Vetter 2016-03-29 8:27 ` Daniel Vetter 2016-03-29 14:05 ` Lyude Paul 2016-03-28 14:33 ` [PATCH v4 RESEND 2/5] drm/dp_helper: Always wait before retrying native aux transactions Lyude 2016-03-28 14:33 ` Lyude 2016-03-28 14:33 ` [PATCH v4 RESEND 3/5] drm/dp_helper: Retry aux transactions on all errors Lyude 2016-03-28 14:33 ` Lyude 2016-03-28 14:33 ` [PATCH v4 RESEND 4/5] drm/dp_helper: Perform throw-away read before actual read in drm_dp_dpcd_read() Lyude 2016-03-28 14:33 ` Lyude 2016-03-29 20:43 ` [PATCH v5 " Lyude 2016-03-29 20:43 ` Lyude 2016-03-28 14:33 ` [PATCH v4 RESEND 5/5] drm/i915: Get rid of intel_dp_dpcd_read_wake() Lyude 2016-03-28 14:33 ` Lyude 2016-03-30 14:26 ` Jani Nikula 2016-03-30 14:26 ` Jani Nikula 2016-04-12 10:17 ` [PATCH v4 RESEND 0/5] Move workarounds from intel_dp_dpcd_read_wake() into drm's DP helpers Jani Nikula 2016-04-12 10:17 ` Jani Nikula 2016-04-12 15:59 ` Lyude 2016-04-12 15:59 ` Lyude 2016-04-13 14:58 ` [PATCH v5 0/4] " Lyude 2016-04-13 14:58 ` Lyude 2016-04-13 14:58 ` [PATCH v5 1/4] drm/dp_helper: Always wait before retrying native aux transactions Lyude 2016-04-13 14:58 ` Lyude 2016-04-13 14:58 ` [PATCH v5 2/4] drm/dp_helper: Retry aux transactions on all errors Lyude 2016-04-13 14:58 ` Lyude 2016-04-13 14:58 ` Lyude [this message] 2016-04-13 14:58 ` [PATCH v5 3/4] drm/dp_helper: Perform throw-away read before actual read in drm_dp_dpcd_read() Lyude 2016-04-14 17:01 ` Ville Syrjälä 2016-04-14 17:01 ` Ville Syrjälä 2016-04-15 14:25 ` [PATCH v6 " Lyude 2016-04-15 14:25 ` Lyude 2016-04-15 14:31 ` Ville Syrjälä 2016-04-15 14:31 ` Ville Syrjälä 2016-04-13 14:58 ` [PATCH v5 4/4] drm/i915: Get rid of intel_dp_dpcd_read_wake() Lyude 2016-04-13 14:58 ` Lyude 2016-04-22 16:54 ` Daniel Vetter 2016-04-22 16:54 ` Daniel Vetter 2016-04-14 10:58 ` ✗ Fi.CI.BAT: failure for series starting with [v5,1/4] drm/dp_helper: Always wait before retrying native aux transactions Patchwork
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