Re: [PATCH] drm/i915: Pretend cursor is always on for ILK-style WM calculations (v2)

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Feb 02, 2016 at 10:06:51PM -0800, Matt Roper wrote:
> Due to our lack of two-step watermark programming, our driver has
> historically pretended that the cursor plane is always on for the
> purpose of watermark calculations; this helps avoid serious flickering
> when the cursor turns off/on (e.g., when the user moves the mouse
> pointer to a different screen).  That workaround was accidentally
> dropped as we started working toward atomic watermark updates.  Since we
> still aren't quite there yet with two-stage updates, we need to
> resurrect the workaround and treat the cursor as always active.
> 
> v2: Tweak cursor width calculations slightly to more closely match the
>     logic we used before the atomic overhaul began.  (Ville)
> 
> Cc: simdev11@outlook.com
> Cc: manfred.kitzbichler@gmail.com
> Reported-by: simdev11@outlook.com
> Reported-by: manfred.kitzbichler@gmail.com
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93892
> Fixes: 43d59eda1 ("drm/i915: Eliminate usage of plane_wm_parameters from ILK-style WM code (v2)")
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 31bc4ea..5888632 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -1799,16 +1799,21 @@ static uint32_t ilk_compute_cur_wm(const struct intel_crtc_state *cstate,
>  				   const struct intel_plane_state *pstate,
>  				   uint32_t mem_value)
>  {
> -	int cpp = pstate->base.fb ?
> -		drm_format_plane_cpp(pstate->base.fb->pixel_format, 0) : 0;
> +	/*
> +	 * We treat the cursor plane as always-on for the purposes of watermark
> +	 * calculation.  Until we have two-stage watermark programming merged,
> +	 * this is necessary to avoid flickering.
> +	 */
> +	int cpp = 4;
> +	int width = pstate->visible ? pstate->base.crtc_w : 64;
>  
> -	if (!cstate->base.active || !pstate->visible)
> +	if (!cstate->base.active)
>  		return 0;
>  
> +

Stray whitespace.

Otherwise lgtm
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

>  	return ilk_wm_method2(ilk_pipe_pixel_rate(cstate),
>  			      cstate->base.adjusted_mode.crtc_htotal,
> -			      drm_rect_width(&pstate->dst),
> -			      cpp, mem_value);
> +			      width, cpp, mem_value);
>  }
>  
>  /* Only for WM_LP. */
> -- 
> 2.1.4
> 
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-- 
Ville Syrjälä
Intel OTC
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