[Intel-gfx] [PATCH] drm/i915/dp: return proper DPRX link training result

[Lee, Shawn C]

On Tue, 2021-07-07, Almahallawy, Khaled <khaled.almahallawy at intel.com> wrote:
>I believe Imre's LT fallback:
>https://github.com/ideak/linux/commits/linktraining-fallback-fix  and Chrome user space fix: 
>https://chromium-review.googlesource.com/c/chromium/src/+/3003487
>should address Chrome concerns for LT failure and LTTPRs
>

Thanks for comment! The new fallback patch should help on this DPRX problem.
One more thing. If driver did not handle DPRX link train failed properly.
It would impact link layer compliance test case in below.

400.3.1.3
400.3.1.4
400.3.1.6
400.3.1.12
400.3.1.13
400.3.1.14

Best regards,
Shawn

>Thanks
>Khaled
>
>On Tue, 2021-07-06 at 23:25 +0800, Lee Shawn C wrote:
>> After DPRX link training, intel_dp_link_train_phy() did not return the 
>> training result properly. If link training failed,
>> i915 driver would not run into link train fallback function.
>> And no hotplug uevent would be received by user space application.
>> 
>> Fixes: b30edfd8d0b4 ("drm/i915: Switch to LTTPR non-transparent mode 
>> link training")
>> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
>> Cc: Imre Deak <imre.deak at intel.com>
>> Cc: Jani Nikula <jani.nikula at linux.intel.com>
>> Cc: Cooper Chiou <cooper.chiou at intel.com>
>> Cc: William Tseng <william.tseng at intel.com>
>> Signed-off-by: Lee Shawn C <shawn.c.lee at intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_dp_link_training.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
>> b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
>> index 08bceae40aa8..e44788b2c564 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
>> @@ -849,7 +849,7 @@ intel_dp_link_train_all_phys(struct intel_dp 
>> *intel_dp,
>>  	}
>>  
>>  	if (ret)
>> -		intel_dp_link_train_phy(intel_dp, crtc_state,
>> DP_PHY_DPRX);
>> +		ret = intel_dp_link_train_phy(intel_dp, crtc_state,
>> DP_PHY_DPRX);
>>  
>>  	if (intel_dp->set_idle_link_train)
>>  		intel_dp->set_idle_link_train(intel_dp, crtc_state);
>