On Mon, 16 Mar 2020, Mario Kleiner mario.kleiner.de@gmail.com wrote:

This fixes a problem found on the MacBookPro 2017 Retina panel.

The panel reports 10 bpc color depth in its EDID, and the firmware chooses link settings at boot which support enough bandwidth for 10 bpc (324000 kbit/sec = multiplier 0xc), but the DP_MAX_LINK_RATE dpcd register only reports 2.7 Gbps (multiplier value 0xa) as possible, in direct contradiction of what the firmware successfully set up.

This restricts the panel to 8 bpc, not providing the full color depth of the panel.

This patch adds a quirk specific to the MBP 2017 15" Retina panel to add the additiional 324000 kbps link rate during edp setup.

Link to previous discussion of a different attempted fix with Ville and Jani:

https://patchwork.kernel.org/patch/11325935/

v2: Follow Jani's proposal of defining quirk_rates[] instead of just appending 324000. This for better clarity.

v3: Rebased onto current drm-tip, as of 16-March-2020. Adapt to new edid_quirks parameter of drm_dp_has_quirk().

Signed-off-by: Mario Kleiner mario.kleiner.de@gmail.com Tested-by: Mario Kleiner mario.kleiner.de@gmail.com Cc: Jani Nikula jani.nikula@intel.com

Pushed to drm-intel-next-queued, thanks for the patch.

BR, Jani.

---

drivers/gpu/drm/drm_dp_helper.c | 2 ++ drivers/gpu/drm/i915/display/intel_dp.c | 11 +++++++++++ include/drm/drm_dp_helper.h | 7 +++++++ 3 files changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index c6fbe6e6bc9d..8ba4531e808d 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -1238,6 +1238,8 @@ 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) },

• /* 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) },

};

#undef OUI diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 0a417cd2af2b..ef2e06e292d5 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -164,6 +164,17 @@ static void intel_dp_set_sink_rates(struct intel_dp *intel_dp) }; int i, max_rate;

• if (drm_dp_has_quirk(&intel_dp->desc, 0,

• 	     DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS)) {
  

• /* Needed, e.g., for Apple MBP 2017, 15 inch eDP Retina panel */
  

• static const int quirk_rates[] = { 162000, 270000, 324000 };
  

• memcpy(intel_dp->sink_rates, quirk_rates, sizeof(quirk_rates));
  

• intel_dp->num_sink_rates = ARRAY_SIZE(quirk_rates);
  

• return;
  

• }

• max_rate = drm_dp_bw_code_to_link_rate(intel_dp->dpcd[DP_MAX_LINK_RATE]);

  for (i = 0; i < ARRAY_SIZE(dp_rates); i++) {

diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index c6119e4c169a..9d87cdf2740a 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -1548,6 +1548,13 @@ enum drm_dp_quirk { * capabilities advertised. */ DP_QUIRK_FORCE_DPCD_BACKLIGHT,

• /**

• * @DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS:
  

• *
  

• * The device supports a link rate of 3.24 Gbps (multiplier 0xc) despite
  

• * the DP_MAX_LINK_RATE register reporting a lower max multiplier.
  

• */
  

• DP_DPCD_QUIRK_CAN_DO_MAX_LINK_RATE_3_24_GBPS,

};

/**