Re: [PATCH 2/3] drm/i915: Deobfuscate wm linetime calculation

["Govindapillai, Vinod" <vinod.govindapillai@intel.com>]

On Fri, 2025-09-19 at 21:08 +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> intel_get_linetime_us() is a mess. Rewrite it in a straightforward
> manner. Also the checks for the !active and pixel_rate==0 are
> completely pointless here since we know that the plane is visible.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/skl_watermark.c | 21 ++++----------------
>  1 file changed, 4 insertions(+), 17 deletions(-)
> 

Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>

> diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c
> b/drivers/gpu/drm/i915/display/skl_watermark.c
> index bdd005c6cc2d..3eaaf26100f1 100644
> --- a/drivers/gpu/drm/i915/display/skl_watermark.c
> +++ b/drivers/gpu/drm/i915/display/skl_watermark.c
> @@ -1636,24 +1636,12 @@ skl_wm_method2(u32 pixel_rate, u32 pipe_htotal, u32 latency,
>  	return ret;
>  }
>  
> -static uint_fixed_16_16_t
> +static int
>  intel_get_linetime_us(const struct intel_crtc_state *crtc_state,
>  		      int pixel_rate)
>  {
> -	struct intel_display *display = to_intel_display(crtc_state);
> -	u32 crtc_htotal;
> -	uint_fixed_16_16_t linetime_us;
> -
> -	if (!crtc_state->hw.active)
> -		return u32_to_fixed16(0);
> -
> -	if (drm_WARN_ON(display->drm, pixel_rate == 0))
> -		return u32_to_fixed16(0);
> -
> -	crtc_htotal = crtc_state->hw.pipe_mode.crtc_htotal;
> -	linetime_us = div_fixed16(crtc_htotal * 1000, pixel_rate);
> -
> -	return linetime_us;
> +	return DIV_ROUND_UP(crtc_state->hw.pipe_mode.crtc_htotal * 1000,
> +			    pixel_rate);
>  }
>  
>  static int
> @@ -1741,8 +1729,7 @@ skl_compute_wm_params(const struct intel_crtc_state *crtc_state,
>  	wp->y_tile_minimum = mul_u32_fixed16(wp->y_min_scanlines,
>  					     wp->plane_blocks_per_line);
>  
> -	wp->linetime_us = fixed16_to_u32_round_up(intel_get_linetime_us(crtc_state,
> -									plane_pixel_rate));
> +	wp->linetime_us = intel_get_linetime_us(crtc_state, plane_pixel_rate);
>  
>  	return 0;
>  }