[Intel-gfx] [PATCH 2/3] drm/i915: Don't enable the cursor on a disable pipe

[Chris Wilson]

On Thu, Sep 12, 2013 at 10:45:42PM +0300, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> On HSW enabling a plane on a disabled pipe may hang the entire system.
> And there's no good reason for doing it ever, so just don't.
> 
> Cc: stable at vger.kernel.org
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 18043a2..d0137b6 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -6793,6 +6793,9 @@ static void intel_crtc_update_cursor(struct drm_crtc *crtc,
>  	u32 base, pos;
>  	bool visible;
>  
> +	if (!intel_crtc->active)
> +		return;

This is misleading since we do expect to call this function whilst
turning off the crtc. This check makes it appear that such calls might
be wrong. Also the !crtc->enabled following intel_crtc->active makes
ones question their sanity.

So I feel this check detracts from readability of the function.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre