[Intel-gfx] [PATCH] Revert "drm/i915: Remove unneeded hack now for CDCLK"

[Jani Nikula]

On Mon, 08 Jun 2020, Stanislav Lisovskiy <stanislav.lisovskiy at intel.com> wrote:
> This reverts commit 82ea174dc5425d4e85e25d0c4ba961a2e494392a.
>

Please explain why. What's going on, why we need the revert.

It's fine to reply here, the commit message can be amended by whoever
applies the patch.

BR,
Jani.


> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> Fixes: cd1915460861 ("drm/i915: Adjust CDCLK accordingly to our DBuf bw needs")
> ---
>  drivers/gpu/drm/i915/display/intel_cdclk.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
> index 08468b121d02..45f7f33d1144 100644
> --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> @@ -2071,6 +2071,18 @@ int intel_crtc_compute_min_cdclk(const struct intel_crtc_state *crtc_state)
>  	/* Account for additional needs from the planes */
>  	min_cdclk = max(intel_planes_min_cdclk(crtc_state), min_cdclk);
>  
> +	/*
> +	 * HACK. Currently for TGL platforms we calculate
> +	 * min_cdclk initially based on pixel_rate divided
> +	 * by 2, accounting for also plane requirements,
> +	 * however in some cases the lowest possible CDCLK
> +	 * doesn't work and causing the underruns.
> +	 * Explicitly stating here that this seems to be currently
> +	 * rather a Hack, than final solution.
> +	 */
> +	if (IS_TIGERLAKE(dev_priv))
> +		min_cdclk = max(min_cdclk, (int)crtc_state->pixel_rate);
> +
>  	if (min_cdclk > dev_priv->max_cdclk_freq) {
>  		drm_dbg_kms(&dev_priv->drm,
>  			    "required cdclk (%d kHz) exceeds max (%d kHz)\n",

-- 
Jani Nikula, Intel Open Source Graphics Center