NAK: [H/I/Unstable/OEM-5.13] [PATCH 1/1] UBUNTU: SAUCE: drm/i915/dp: Use max params for older panels

[Kleber Souza]

On 09.08.21 07:09, Kai-Heng Feng wrote:
> BugLink: https://bugs.launchpad.net/bugs/1936708
> 
> Users reported that after commit 2bbd6dba84d4 ("drm/i915: Try to use
> fast+narrow link on eDP again and fall back to the old max strategy on
> failure"), the screen starts to have wobbly effect.
> 
> Commit a5c936add6a2 ("drm/i915/dp: Use slow and wide link training for
> everything") doesn't help either, that means the affected panels only
> work with max params.
> 
> The panels are all DP 1.1 ones, so apply max params to them to resolve
> the issue.
> 
> Link: https://patchwork.kernel.org/project/intel-gfx/list/?series=526397
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3714
> Fixes: 2bbd6dba84d4 ("drm/i915: Try to use fast+narrow link on eDP again and fall back to the old max strategy on failure")
> Fixes: a5c936add6a2 ("drm/i915/dp: Use slow and wide link training for everything")
> Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
> ---
>   drivers/gpu/drm/i915/display/intel_dp.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 6cc03b9e4321a..eb1ed8990ca03 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1338,14 +1338,16 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>   	limits.min_bpp = intel_dp_min_bpp(pipe_config->output_format);
>   	limits.max_bpp = intel_dp_max_bpp(intel_dp, pipe_config);
>   
> -	if (intel_dp->use_max_params) {
> +	if (intel_dp->use_max_params ||
> +	    intel_dp->dpcd[DP_DPCD_REV] <= DP_DPCD_REV_11) {
>   		/*
>   		 * Use the maximum clock and number of lanes the eDP panel
>   		 * advertizes being capable of in case the initial fast
> -		 * optimal params failed us. The panels are generally
> -		 * designed to support only a single clock and lane
> -		 * configuration, and typically on older panels these
> -		 * values correspond to the native resolution of the panel.
> +		 * optimal params failed us or the panel is DP 1.1 or earlier.
> +		 * The panels are generally designed to support only a single
> +		 * clock and lane configuration, and typically on older panels
> +		 * these values correspond to the native resolution of the
> +		 * panel.
>   		 */
>   		limits.min_lane_count = limits.max_lane_count;
>   		limits.min_clock = limits.max_clock;
> 

What ended up being accepted, at least in drm-intel-next for now, was a v3
of this patch fixing some corner cases not spotted on this first version:

https://cgit.freedesktop.org/drm/drm-intel/commit/?h=drm-intel-next&id=d7f213c131adf0bec8b731553eb82990cdac265d

So I'm NAKing it for any stable releases until we have v3 backported/cherry-picked
and submitted again.

Also, what should we do about I/U/OEM-5.13 which already got the incomplete
version of the fix?


Kleber