[Intel-gfx] [PATCH] drm/i915: Add more latency to avoid display flicker

[Mahesh Kumar]

Hi,

Adding random latency is not a right solution for any flicker.
This will affect the configuration which can be supported in all other 
platforms.
There are many unanswered questions here:
Which customer? which platform? changes & root-cause of the issue?

Please find what are the changes in customer board & according to 
root-cause of issue add WA with proper reasoning & only for affected 
platforms.

-Mahesh


On Tuesday 22 August 2017 05:06 PM, Lee, Shawn C wrote:
> From: "Lee, Shawn C" <shawn.c.lee at intel.com>
>
> LFP flicker with latest drm-nightly on customer board. After increase
> latency value and this symptom can't be reproduced.
>
> TEST=Reboot DUT and no flicking on LFP.
>
> Cc: Kumar, Mahesh <mahesh1.kumar at intel.com>
> Cc: Gary C Wang <gary.c.wang at intel.com>
>
> Signed-off-by: Shawn Lee <shawn.c.lee at intel.com>
> ---
>   drivers/gpu/drm/i915/intel_pm.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index e7ab17d38680..2faea497e00c 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4410,7 +4410,7 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
>   		latency += 4;
>   
>   	if (apply_memory_bw_wa && x_tiled)
> -		latency += 15;
> +		latency += 60;
>   
>   	if (plane->id == PLANE_CURSOR) {
>   		width = intel_pstate->base.crtc_w;