[PATCH v4 08/30] drm/dp_mst: Add HBLANK expansion quirk for Synaptics MST hubs

[Imre Deak]

Add a quirk for Synaptics MST hubs, which require a workaround - at leat
on i915 - for some modes, on which the hub applies HBLANK expansion.
These modes will only work by enabling DSC decompression for them, a
follow-up patch will do this in i915.

v2:
- Fix the quirk name in its DocBook description.

Cc: Lyude Paul <lyude at redhat.com>
Cc: dri-devel at lists.freedesktop.org
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/display/drm_dp_helper.c | 2 ++
 include/drm/display/drm_dp_helper.h     | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
index f3680f4e69708..e5d7970a9ddd0 100644
--- a/drivers/gpu/drm/display/drm_dp_helper.c
+++ b/drivers/gpu/drm/display/drm_dp_helper.c
@@ -2245,6 +2245,8 @@ static const struct dpcd_quirk dpcd_quirk_list[] = {
 	{ OUI(0x00, 0x00, 0x00), DEVICE_ID('C', 'H', '7', '5', '1', '1'), false, BIT(DP_DPCD_QUIRK_NO_SINK_COUNT) },
 	/* Synaptics DP1.4 MST hubs can support DSC without virtual DPCD */
 	{ OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true, BIT(DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) },
+	/* Synaptics DP1.4 MST hubs require DSC for some modes on which it applies HBLANK expansion. */
+	{ OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true, BIT(DP_DPCD_QUIRK_HBLANK_EXPANSION_REQUIRES_DSC) },
 	/* Apple MacBookPro 2017 15 inch eDP Retina panel reports too low DP_MAX_LINK_RATE */
 	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID(101, 68, 21, 101, 98, 97), false, BIT(DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS) },
 };
diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
index 3d74b2cec72fd..da94932f4262b 100644
--- a/include/drm/display/drm_dp_helper.h
+++ b/include/drm/display/drm_dp_helper.h
@@ -632,6 +632,13 @@ enum drm_dp_quirk {
 	 * the DP_MAX_LINK_RATE register reporting a lower max multiplier.
 	 */
 	DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS,
+	/**
+	 * @DP_DPCD_QUIRK_HBLANK_EXPANSION_REQUIRES_DSC:
+	 *
+	 * The device applies HBLANK expansion for some modes, but this
+	 * requires enabling DSC.
+	 */
+	DP_DPCD_QUIRK_HBLANK_EXPANSION_REQUIRES_DSC,
 };
 
 /**
-- 
2.39.2