On Wed, Apr 04, 2018 at 10:22:21AM +0200, Thomas Hellstrom wrote: > Hi, > > On 04/04/2018 08:58 AM, Daniel Vetter wrote: > > On Wed, Apr 4, 2018 at 12:42 AM, Rob Clark <robdclark@xxxxxxxxx> wrote: > > > Add an atomic helper to implement dirtyfb support. This is needed to > > > support DSI command-mode panels with x11 userspace (ie. when we can't > > > rely on pageflips to trigger a flush to the panel). > > > > > > To signal to the driver that the async atomic update needs to > > > synchronize with fences, even though the fb didn't change, the > > > drm_atomic_state::dirty flag is added. > > > > > > Signed-off-by: Rob Clark <robdclark@xxxxxxxxx> > > > --- > > > Background: there are a number of different folks working on getting > > > upstream kernel working on various different phones/tablets with qcom > > > SoC's.. many of them have command mode panels, so we kind of need a > > > way to support the legacy dirtyfb ioctl for x11 support. > > > > > > I know there is work on a proprer non-legacy atomic property for > > > userspace to communicate dirty-rect(s) to the kernel, so this can > > > be improved from triggering a full-frame flush once that is in > > > place. But we kinda needa a stop-gap solution. > > > > > > I had considered an in-driver solution for this, but things get a > > > bit tricky if userspace ands up combining dirtyfb ioctls with page- > > > flips, because we need to synchronize setting various CTL.FLUSH bits > > > with setting the CTL.START bit. (ie. really all we need to do for > > > cmd mode panels is bang CTL.START, but is this ends up racing with > > > pageflips setting FLUSH bits, then bad things.) The easiest soln > > > is to wrap this up as an atomic commit and rely on the worker to > > > serialize things. Hence adding an atomic dirtyfb helper. > > > > > > I guess at least the helper, with some small addition to translate > > > and pass-thru the dirty rect(s) is useful to the final atomic dirty- > > > rect property solution. Depending on how far off that is, a stop- > > > gap solution could be useful. > > Adding Noralf, who iirc already posted the full dirty helpers already somewhere. > > -Daniel > > I've asked Deepak to RFC the core changes suggested for the full dirty blob > on dri-devel. It builds on DisplayLink's suggestion, with a simple helper to > get to the desired coordinates. > > One thing to perhaps discuss is how we would like to fit this with > front-buffer rendering and the dirty ioctl. In the page-flip context, the > dirty rects, like egl's swapbuffer_with_damage is a hint to restrict the > damage region that can be fully ignored by the driver, new content is > indicated by a new framebuffer. > > We could do the same for frontbuffer rendering: Either set a dirty flag like > you do here, or provide a content_age state member. Since we clear the dirty > flag on state copies, I guess that would be sufficient. The blob rectangles > would then become a hint to restrict the damage region. I'm not entirely following here - I thought for frontbuffer rendering the dirty rects have always just been a hint, and that the driver was always free to re-upload the entire buffer to the screen. And through a helper like Rob's proposing here (and have floated around in different versions already) we'd essentially map a frontbuffer dirtyfb call to a fake flip with dirty rect. Manual upload drivers already need to upload the entire screen if they get a flip, since some userspace uses that to flush out frontbuffer rendering (instead of calling dirtyfb). So from that pov the new dirty flag is kinda not necessary imo. > Another approach would be to have the presence of dirty rects without > framebuffer change to indicate frontbuffer rendering. > > I think I like the first approach best, although it may be tempting for > user-space apps to just set the dirty bit instead of providing the full > damage region. Or I'm not following you here, because I don't quite see the difference between dirtyfb and a flip. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
