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SubjectRe: [PATCH] drm/atmel-hlcdc: prevent divide by zero
On Tue, Jan 08, 2019 at 12:31:36PM +0000, Peter Rosin wrote:
> While trying to temporarily hide a plane, one thing that was attempted
> was to call (from libdrm)
>
> drmModeSetPlane(fd, plane_id, crtc_id, fb_id, 0,
> 0, 0, 0, 0, 0, 0, 0, 0);
>
> This call causes a pair of "Division by zero in kernel." messages. Kill
> those messages, but preserve the current behaviour that also happen to
> make the plane disappear with the above call.
>
> Signed-off-by: Peter Rosin <peda@axentia.se>
> ---
> drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> Side note, when comparing with drm_atomic_helper_check_plane_state(), I get
> the feeling that the src rect should be clipped together with the crtc rect
> if/when clipping is needed. That function calls drm_rect_clip_scaled(), and
> the equivalent does not seem to happen here. Should clipping be performed
> on the src rect?

Any reasons atmel can't switch over to that helper? Would compute a nice
->visible state variable for you ...
-Daniel

>
> Cheers,
> Peter
>
> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c
> index 3cc489b870fe..1bdb30dc218c 100644
> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c
> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c
> @@ -675,10 +675,16 @@ static int atmel_hlcdc_plane_atomic_check(struct drm_plane *p,
> state->crtc_y = 0;
> }
>
> - patched_src_w = DIV_ROUND_CLOSEST(patched_crtc_w * state->src_w,
> - state->crtc_w);
> - patched_src_h = DIV_ROUND_CLOSEST(patched_crtc_h * state->src_h,
> - state->crtc_h);
> + if (state->crtc_w)
> + patched_src_w = DIV_ROUND_CLOSEST(patched_crtc_w * state->src_w,
> + state->crtc_w);
> + else
> + patched_src_w = 0;
> + if (state->crtc_h)
> + patched_src_h = DIV_ROUND_CLOSEST(patched_crtc_h * state->src_h,
> + state->crtc_h);
> + else
> + patched_src_h = 0;
>
> hsub = drm_format_horz_chroma_subsampling(fb->format->format);
> vsub = drm_format_vert_chroma_subsampling(fb->format->format);
> --
> 2.11.0
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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