[PATCH 2/3] drm/i915/watermark: Modify latency programmed into PKG_C_LATENCY

[Golani, Mitulkumar Ajitkumar]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Suraj
> Kandpal
> Sent: 11 November 2024 18:03
> To: intel-xe at lists.freedesktop.org; intel-gfx at lists.freedesktop.org
> Cc: Govindapillai, Vinod <vinod.govindapillai at intel.com>; Kandpal, Suraj
> <suraj.kandpal at intel.com>
> Subject: [PATCH 2/3] drm/i915/watermark: Modify latency programmed into
> PKG_C_LATENCY
> 
> Increase the latency programmed into PKG_C_LATENCY latency to be a
> multiple of line time which is written into WM_LINETIME.
> 
> --v2
> -Fix commit subject line [Sai Teja]
> -Use individual DISPLAY_VER checks instead of range [Sai Teja] -Initialize
> max_linetime [Sai Teja]
> 
> --v3
> -take into account the scenario when adjusted_latency is 0 [Vinod]
> 
> WA: 22020299601
> Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> ---
>  drivers/gpu/drm/i915/display/skl_watermark.c | 26 ++++++++++++++------
>  1 file changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c
> b/drivers/gpu/drm/i915/display/skl_watermark.c
> index a97e90ac643f..e061015a89b0 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)
>  {
> -	u32 max_latency = LNL_PKG_C_LATENCY_MASK;
> +	u32 adjusted_latency = LNL_PKG_C_LATENCY_MASK;
>  	u32 clear = 0, val = 0;
>  	u32 added_wake_time = 0;
> 
> @@ -2858,15 +2860,22 @@ 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);
> +
> +		/* Wa_22020299601 */
> +		if ((DISPLAY_VER(i915) == 20 || DISPLAY_VER(i915) == 30) &&
> +		    adjusted_latency != 0)
> +			adjusted_latency = max_linetime *
> +				DIV_ROUND_UP(adjusted_latency,
> max_linetime);
> +		else
> +			adjusted_latency = LNL_PKG_C_LATENCY_MASK;

You are already initialized it on the first instance, and wrote a patch #1 to get rid of duplicate of initialization. But why again ?
Also any reason to move away from 'max_latency' to 'adjusted_latency' ?
all I can read through your commit message is, you are making this latency as multiple of linetime, any adjustment we are making ?

> +
>  		added_wake_time = DSB_EXE_TIME +
>  			i915->display.sagv.block_time_us;
>  	}
> 
>  	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);

Also you can think of this combine with below line for simplification ?

>  	val |= REG_FIELD_PREP(LNL_ADDED_WAKE_TIME_MASK,
> added_wake_time);
> 
>  	intel_uncore_rmw(&i915->uncore, LNL_PKG_C_LATENCY, clear, val);
> @@ -2879,6 +2888,7 @@ 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 = 0;
> 
>  	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
>  		ret = skl_build_pipe_wm(state, crtc); @@ -2908,9 +2918,11
> @@ 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);
> 
> --
> 2.34.1