[PATCH 1/3] i915/display/intel_dp: Read PCON DSC ENC caps only for DPCD rev >= 1.4

[Nautiyal, Ankit K]

On 2/8/2021 4:45 PM, Jani Nikula wrote:
> On Thu, 04 Feb 2021, Ankit Nautiyal <ankit.k.nautiyal at intel.com> wrote:
>> DP-HDMI2.1 PCON has DSC encoder caps defined in registers 0x92-0x9E.
>> Do not read the registers if DPCD rev < 1.4.
>>
>> Fixes: https://gitlab.freedesktop.org/drm/intel/-/issues/2868
> Please use Fixes: to reference commits that this patch fixes.
>
> Please use Closes: to reference issues that this patch fixes.
>
> No need to resend for this, can be fixed while applying, but please tell
> me the commit that introduced the problem.
>
> BR,
> Jani.
>
Alright will take care. Please find below the commit that introduced this:

b9d96dacdc3d983eae234b52401edb56dbceb764

Patch : drm/i915: Read DSC capabilities of the HDMI2.1 PCON encoder 
https://patchwork.freedesktop.org/patch/408779/


Thanks & Regards,

Ankit

>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_dp.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index 8c12d5375607..2b83f0f433a2 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -2489,9 +2489,11 @@ static void intel_dp_get_pcon_dsc_cap(struct intel_dp *intel_dp)
>>   	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
>>   
>>   	/* Clear the cached register set to avoid using stale values */
>> -
>>   	memset(intel_dp->pcon_dsc_dpcd, 0, sizeof(intel_dp->pcon_dsc_dpcd));
>>   
>> +	if (intel_dp->dpcd[DP_DPCD_REV] < 0x14)
>> +		return;
>> +
>>   	if (drm_dp_dpcd_read(&intel_dp->aux, DP_PCON_DSC_ENCODER,
>>   			     intel_dp->pcon_dsc_dpcd,
>>   			     sizeof(intel_dp->pcon_dsc_dpcd)) < 0)