On Fri, May 15, 2020 at 08:58:02AM +0200, Thomas Zimmermann wrote: > Hi > > Am 14.05.20 um 22:36 schrieb Rob Herring: > > On Thu, May 14, 2020 at 7:40 AM Daniel Vetter <daniel@xxxxxxxx> wrote: > >> > >> On Wed, May 13, 2020 at 05:03:11PM +0200, Thomas Zimmermann wrote: > >>> SHMEM-buffer backing storage is allocated from system memory; which is > >>> typically cachable. Currently, only virtio uses cachable mappings; udl > >>> uses its own vmap/mmap implementation for cachable mappings. Other > >>> drivers default to writecombine mappings. > >> > >> I'm pretty sure this breaks all these drivers. quick grep on a few > >> functions says this is used by lima, panfrost, v3d. And they definitely > >> need uncached/wc stuff afaiui. Or I'm completely missing something? > > > > OK. I think I'll just make a patch that adds a .gem_create_object helper > that sets the map_cached flag. So drivers can opt-in. > > > Yes, that would be my guess. DMA is usually non-coherent on Arm. > > Can one of you give me some pointer to what you're looking at? For > example, I grepped for use of vmap within lima and only found [1]. > That's a for memcpy with no DMA involved. There's got to be something > I'm missing. > > Best regards > Thomas > > [1] > https://cgit.freedesktop.org/drm/drm-tip/tree/drivers/gpu/drm/lima/lima_sched.c#n391 $ git grep drm_gem_shmem_mmap We also need correct access from userspace, otherwise the gpu is going to be sad. -Daniel > > > > > Rob > > > > -- > Thomas Zimmermann > Graphics Driver Developer > SUSE Software Solutions Germany GmbH > Maxfeldstr. 5, 90409 Nürnberg, Germany > (HRB 36809, AG Nürnberg) > Geschäftsführer: Felix Imendörffer > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
