Re: [PATCH] drm/i914/watermark: Modify latency programmed into PKG_C_LATENCY

["Pottumuttu, Sai Teja" <sai.teja.pottumuttu@intel.com>]

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On 07-11-2024 17:02, Suraj Kandpal wrote:
> Increase the latency programmed into PKG_C_LATENCY latency to be
> a multiple of line time which is written into WM_LINETIME.

The commit subject prefix should be drm/i915/watermark (its i914 currently)

> WA: 22020299601
> Signed-off-by: Suraj Kandpal<suraj.kandpal@intel.com>
> ---
>   drivers/gpu/drm/i915/display/skl_watermark.c | 26 ++++++++++++++------
>   1 file changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c b/drivers/gpu/drm/i915/display/skl_watermark.c
> index d3bbf335c749..856b20a683fd 100644
> --- a/drivers/gpu/drm/i915/display/skl_watermark.c
> +++ b/drivers/gpu/drm/i915/display/skl_watermark.c
> @@ -2848,9 +2848,11 @@ static int skl_wm_add_affected_planes(struct intel_atomic_state *state,
>    * Program PKG_C_LATENCY Added Wake Time = 0
>    */
>   static void
> -skl_program_dpkgc_latency(struct drm_i915_private *i915, bool enable_dpkgc)
> +skl_program_dpkgc_latency(struct drm_i915_private *i915,
> +			  bool enable_dpkgc,
> +			  u32 max_linetime)

Nit: This ^ argument can fit in the line before.

>   {
> -	u32 max_latency = 0;
> +	u32 adjusted_latency = 0;
>   	u32 clear = 0, val = 0;
>   	u32 added_wake_time = 0;
>   
> @@ -2858,18 +2860,23 @@ skl_program_dpkgc_latency(struct drm_i915_private *i915, bool enable_dpkgc)
>   		return;
>   
>   	if (enable_dpkgc) {
> -		max_latency = skl_watermark_max_latency(i915, 1);
> -		if (max_latency == 0)
> -			max_latency = LNL_PKG_C_LATENCY_MASK;
> +		adjusted_latency = skl_watermark_max_latency(i915, 1);
> +		if (adjusted_latency == 0)
> +			adjusted_latency = LNL_PKG_C_LATENCY_MASK;
> +
> +		/* Wa_22020299601 */
> +		if (IS_DISPLAY_VERx100(i915, 2000, 3000))

This wa is applicable only to IP versions 2000 and 3000. So, shouldn't 
we be limiting this to only those IP versions instead of the full range?

> +			adjusted_latency = max_linetime *
> +				DIV_ROUND_UP(adjusted_latency, max_linetime);
>   		added_wake_time = DSB_EXE_TIME +
>   			i915->display.sagv.block_time_us;
>   	} else {
> -		max_latency = LNL_PKG_C_LATENCY_MASK;
> +		adjusted_latency = LNL_PKG_C_LATENCY_MASK;
>   		added_wake_time = 0;
>   	}
>   
>   	clear |= LNL_ADDED_WAKE_TIME_MASK | LNL_PKG_C_LATENCY_MASK;
> -	val |= REG_FIELD_PREP(LNL_PKG_C_LATENCY_MASK, max_latency);
> +	val |= REG_FIELD_PREP(LNL_PKG_C_LATENCY_MASK, adjusted_latency);
>   	val |= REG_FIELD_PREP(LNL_ADDED_WAKE_TIME_MASK, added_wake_time);
>   
>   	intel_uncore_rmw(&i915->uncore, LNL_PKG_C_LATENCY, clear, val);
> @@ -2882,6 +2889,7 @@ skl_compute_wm(struct intel_atomic_state *state)
>   	struct intel_crtc_state __maybe_unused *new_crtc_state;
>   	int ret, i;
>   	bool enable_dpkgc = false;
> +	u32 max_linetime;

max_linetime should be initialized to 0 I believe so that the max 
comparison works correctly below.

Thanks
Sai Teja

>   
>   	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
>   		ret = skl_build_pipe_wm(state, crtc);
> @@ -2911,9 +2919,11 @@ skl_compute_wm(struct intel_atomic_state *state)
>   		     new_crtc_state->vrr.vmin == new_crtc_state->vrr.flipline) ||
>   		    !new_crtc_state->vrr.enable)
>   			enable_dpkgc = true;
> +
> +		max_linetime = max(new_crtc_state->linetime, max_linetime);
>   	}
>   
> -	skl_program_dpkgc_latency(to_i915(state->base.dev), enable_dpkgc);
> +	skl_program_dpkgc_latency(to_i915(state->base.dev), enable_dpkgc, max_linetime);
>   
>   	skl_print_wm_changes(state);
>   

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