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* [PATCH] drm/dp_mst: Fix DSC decompression detection in Synaptics branch devices
@ 2024-09-09 14:46 Imre Deak
  2024-09-09 20:51 ` ✓ Fi.CI.BAT: success for " Patchwork
                   ` (2 more replies)
  0 siblings, 3 replies; 5+ messages in thread
From: Imre Deak @ 2024-09-09 14:46 UTC (permalink / raw)
  To: intel-gfx, dri-devel; +Cc: Lyude Paul

Atm it's assumed that all Synaptics MST branch devices support DSC,
which is not exposed via a DP-to-DP peer device, rather a control flag
in the branch device's UFP DPCD applying to all the streams going
through it. This isn't true for all adapters with this branch device
though (for instance the Cakitte USBC->2xHDMI adapter reported in the
Closes link below doesn't support DSC).

Fix the above by advertising the DSC decompression support only if the
capability flag for this in the UFP DPCD is actually set.

Cc: Lyude Paul <lyude@redhat.com>
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12047
Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/display/drm_dp_mst_topology.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index a040d7dfced17..ac90118b9e7a8 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -6083,6 +6083,7 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
 	struct drm_dp_aux *immediate_upstream_aux;
 	struct drm_dp_mst_port *fec_port;
 	struct drm_dp_desc desc = {};
+	u8 upstream_dsc;
 	u8 endpoint_fec;
 	u8 endpoint_dsc;
 
@@ -6109,8 +6110,6 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
 
 	/* DP-to-DP peer device */
 	if (drm_dp_mst_is_virtual_dpcd(immediate_upstream_port)) {
-		u8 upstream_dsc;
-
 		if (drm_dp_dpcd_read(&port->aux,
 				     DP_DSC_SUPPORT, &endpoint_dsc, 1) != 1)
 			return NULL;
@@ -6156,6 +6155,13 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
 	if (drm_dp_has_quirk(&desc, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD)) {
 		u8 dpcd_ext[DP_RECEIVER_CAP_SIZE];
 
+		if (drm_dp_dpcd_read(immediate_upstream_aux,
+				     DP_DSC_SUPPORT, &upstream_dsc, 1) != 1)
+			return NULL;
+
+		if (!(upstream_dsc & DP_DSC_DECOMPRESSION_IS_SUPPORTED))
+			return NULL;
+
 		if (drm_dp_read_dpcd_caps(immediate_upstream_aux, dpcd_ext) < 0)
 			return NULL;
 
-- 
2.44.2


^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2024-09-12 10:34 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2024-09-09 14:46 [PATCH] drm/dp_mst: Fix DSC decompression detection in Synaptics branch devices Imre Deak
2024-09-09 20:51 ` ✓ Fi.CI.BAT: success for " Patchwork
2024-09-10 19:34 ` [PATCH] " Lyude Paul
2024-09-10 23:07 ` ✗ Fi.CI.IGT: failure for " Patchwork
2024-09-12 10:35   ` Imre Deak

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