From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Brezillon Subject: Re: [PATCH] drm/atmel-hlcdc: prevent divide by zero Date: Wed, 9 Jan 2019 13:00:08 +0100 Message-ID: <20190109125833.0af5dc52@bbrezillon> References: <20190108123129.20031-1-peda@axentia.se> <20190109101224.GT21184@phenom.ffwll.local> <9b73f5fa-e5c2-ea55-8d96-be6de8a1f34a@axentia.se> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <9b73f5fa-e5c2-ea55-8d96-be6de8a1f34a@axentia.se> Sender: linux-kernel-owner@vger.kernel.org To: Peter Rosin Cc: "linux-kernel@vger.kernel.org" , Alexandre Belloni , David Airlie , Nicolas Ferre , "dri-devel@lists.freedesktop.org" , Boris Brezillon , "linux-arm-kernel@lists.infradead.org" List-Id: dri-devel@lists.freedesktop.org On Wed, 9 Jan 2019 11:37:19 +0000 Peter Rosin wrote: > On 2019-01-09 11:12, Daniel Vetter wrote: > > 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 > >> --- > >> 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 > > I have not researched that, and as stated above, I was not sure if that was the > correct approach to begin with. Boris, any insights? You can look at vc4_plane.c if you want an example of how this helper can be used to get clipped dimensions of the plane. > Does this code predate the > helper or something? Yes, and I must admit I'm not actively maintaining the driver, so there are probably a few other things we could simplify by using generic helpers. > > Maybe there's some register bit that hides a plane explicitly, matching the > ->visible state variable? I haven't looked at that either... I don't think so, but you can simply disable the plane when ->visible is false.