Re: [PATCH] drm/i915/pfit: Prevent negative coordinates in center mode

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

On Tue, Mar 31, 2026 at 11:10:44PM +0530, Nemesa Garg wrote:
> When the pipe_src width or height are greater than adjusted_mode hdisplay
> and vdisplay, computed x and y offsets for center mode can be negative.
> Writing negative values into the pch_fit registers result in a state error.
> Add a check to clamp these values so that they are never negative.
> 
> Signed-off-by: Nemesa Garg <nemesa.garg@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_pfit.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_pfit.c b/drivers/gpu/drm/i915/display/intel_pfit.c
> index 6dda496190e0..1507c2b5b5c7 100644
> --- a/drivers/gpu/drm/i915/display/intel_pfit.c
> +++ b/drivers/gpu/drm/i915/display/intel_pfit.c
> @@ -186,6 +186,7 @@ static int pch_panel_fitting(struct intel_crtc_state *crtc_state,
>  			     const struct drm_connector_state *conn_state)
>  {
>  	struct intel_display *display = to_intel_display(crtc_state);
> +	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
>  	const struct drm_display_mode *adjusted_mode =
>  		&crtc_state->hw.adjusted_mode;
>  	int pipe_src_w = drm_rect_width(&crtc_state->pipe_src);
> @@ -204,6 +205,16 @@ static int pch_panel_fitting(struct intel_crtc_state *crtc_state,
>  		height = pipe_src_h;
>  		x = (adjusted_mode->crtc_hdisplay - width + 1)/2;
>  		y = (adjusted_mode->crtc_vdisplay - height + 1)/2;
> +		if (adjusted_mode->crtc_hdisplay < width ||
> +		    adjusted_mode->crtc_vdisplay < height) {
> +			drm_dbg_kms(display->drm,
> +				    "[CRTC:%d:%s] pfit center mode source (%dx%d) exceeds display (%dx%d)\n",
> +				    crtc->base.base.id, crtc->base.name,
> +				    width, height,

width,height represent the pfit output window size. So I think it'd
be better to do the check in terms of pipe_src_w,pipe_src_h.

And I guess then we can do it before we even compute x,y,width,height.

> +				    adjusted_mode->crtc_hdisplay,
> +				    adjusted_mode->crtc_vdisplay);
> +			return -EINVAL;
> +		}
>  		break;
>  
>  	case DRM_MODE_SCALE_ASPECT:
> -- 
> 2.25.1

-- 
Ville Syrjälä
Intel