Re: [Intel-gfx] [PATCH] drm/i915/dp: Add dpcd link_rate quirk for Apple 15" MBP 2017 (v2)

[Jani Nikula <jani.nikula@intel.com>]

On Thu, 05 Mar 2020, Jani Nikula <jani.nikula@intel.com> wrote:
> On Thu, 05 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.
>>
>> Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
>> Tested-by: Mario Kleiner <mario.kleiner.de@gmail.com>
>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> Cc: Jani Nikula <jani.nikula@intel.com>
>
> As much as I dislike quirks, I think we did exhaust other options when
> we debugged this, and this is now very nicely isolated. Thanks for the
> patch.
>
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
>
> I'll merge once the CI results are in, mostly to ensure this doesn't
> impact other platforms, as we don't have the machine in the CI farm.

Note to self, add this when merging per Mario's suggestion:

Cc: stable@vger.kernel.org

>
>> ---
>>  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 5a103e9b3c86..36a371c016cb 100644
>> --- a/drivers/gpu/drm/drm_dp_helper.c
>> +++ b/drivers/gpu/drm/drm_dp_helper.c
>> @@ -1179,6 +1179,8 @@ 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 4074d83b1a5f..c0d2c70b04fb 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -169,6 +169,17 @@ static void intel_dp_set_sink_rates(struct intel_dp *intel_dp)
>>  	};
>>  	int i, max_rate;
>>  
>> +	if (drm_dp_has_quirk(&intel_dp->desc,
>> +			     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 262faf9e5e94..4b86a1f2a559 100644
>> --- a/include/drm/drm_dp_helper.h
>> +++ b/include/drm/drm_dp_helper.h
>> @@ -1532,6 +1532,13 @@ enum drm_dp_quirk {
>>  	 * The DSC caps can be read from the physical aux instead.
>>  	 */
>>  	DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD,
>> +	/**
>> +	 * @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,
>>  };
>>  
>>  /**

-- 
Jani Nikula, Intel Open Source Graphics Center
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