On Mon, Jul 10, 2017 at 11:58 PM, Daniel Vetter <daniel@xxxxxxxx> wrote: > On Fri, Jul 7, 2017 at 7:48 AM, Dawid Kurek <dawid.kurek@xxxxxxxxxxxxxxx> wrote: >> In page_flip vblank is sent with no delay. Driver does not know when the >> actual update is present on the display and has no means for getting >> this information from a device. It is practically impossible to say >> exactly *when* as there is also i.e. a usb delay. >> >> When we are unable to determine when the vblank actually happens we may >> assume it will behave accordingly, i.e. it will present frames with >> proper timing. In the worst case scenario it should take up to duration >> of one frame (we may get new frame in the device just after presenting >> current one so we would need to wait for the whole frame). >> >> Because of the asynchronous nature of the delay we need to synchronize: >> * read/write vrefresh/page_flip data when changing mode and >> preparing/executing vblank >> * USB requests to prevent interleaved access to URBs for two different >> frame buffers >> >> All those changes are backports from ChromeOS: >> 1. https://chromium-review.googlesource.com/250622 >> 2. https://chromium-review.googlesource.com/249450 >> partially, only change in udl_modeset.c for 'udl_flip_queue' >> 3. https://chromium-review.googlesource.com/321378 >> 4. https://chromium-review.googlesource.com/324119 >> + fixes for checkpatch and latest drm changes >> >> Cc: hshi@xxxxxxxxxxxx >> Cc: marcheu@xxxxxxxxxxxx >> Cc: zachr@xxxxxxxxxxxx >> Cc: dbehr@xxxxxxxxxx >> Signed-off-by: Dawid Kurek <dawid.kurek@xxxxxxxxxxxxxxx> > > Can't we roll this driver over to the atomic helpers instead? There > you get nonblocking pretty much for free ... I'm not sure extending > the old modeset code has all that much benefit really. This code certainly has value by itself; it makes the driver more efficient. I think the best can sometimes be the enemy of the good -- this code is here and written, but I don't think any of us is going to tackle atomic for udl. Stéphane > -Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
