Re: noveau vs arm dma ops

(While there's a rain shower...) On Thu, Apr 26, 2018 at 02:09:42AM -0700, Christoph Hellwig wrote: > synopsis: > > drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c:pdevinfo.dma_mask > = DMA_BIT_MASK(32); > drivers/gpu/drm/bridge/synopsys/dw-hdmi.c: pdevinfo.dma_mask =

Re: noveau vs arm dma ops

On Thu, Apr 26, 2018 at 11:09 AM, Christoph Hellwig wrote: > On Wed, Apr 25, 2018 at 11:35:13PM +0200, Daniel Vetter wrote: >> > get_required_mask() is supposed to tell you if you are safe. However >> > we are missing lots of implementations of it for iommus so you might get

Re: [Linaro-mm-sig] noveau vs arm dma ops

On Thu, Apr 26, 2018 at 11:24 AM, Christoph Hellwig wrote: > On Thu, Apr 26, 2018 at 11:20:44AM +0200, Daniel Vetter wrote: >> The above is already what we're implementing in i915, at least >> conceptually (it all boils down to clflush instructions because those >> both

Re: [Linaro-mm-sig] noveau vs arm dma ops

On Thu, Apr 26, 2018 at 11:20:44AM +0200, Daniel Vetter wrote: > The above is already what we're implementing in i915, at least > conceptually (it all boils down to clflush instructions because those > both invalidate and flush). The clwb instruction that just writes back dirty cache lines might

Re: [Linaro-mm-sig] noveau vs arm dma ops

On Thu, Apr 26, 2018 at 12:54 AM, Russell King - ARM Linux wrote: > On Wed, Apr 25, 2018 at 08:33:12AM -0700, Christoph Hellwig wrote: >> On Wed, Apr 25, 2018 at 12:04:29PM +0200, Daniel Vetter wrote: >> > - dma api hides the cache flushing requirements from us. GPUs love

Re: noveau vs arm dma ops

On Thu, Apr 26, 2018 at 1:26 AM, Russell King - ARM Linux wrote: > On Wed, Apr 25, 2018 at 11:35:13PM +0200, Daniel Vetter wrote: >> On arm that doesn't work. The iommu api seems like a good fit, except >> the dma-api tends to get in the way a bit (drm/msm apparently has >>

Re: noveau vs arm dma ops

On Wed, Apr 25, 2018 at 11:54:43PM +0100, Russell King - ARM Linux wrote: > > if the memory was previously dirty (iow, CPU has written), you need to > flush the dirty cache lines _before_ the GPU writes happen, but you > don't know whether the CPU has speculatively prefetched, so you need > to

Re: noveau vs arm dma ops

On Wed, Apr 25, 2018 at 11:35:13PM +0200, Daniel Vetter wrote: > > get_required_mask() is supposed to tell you if you are safe. However > > we are missing lots of implementations of it for iommus so you might get > > some false negatives, improvements welcome. It's been on my list of > > things

Re: noveau vs arm dma ops

On Wed, Apr 25, 2018 at 11:35:13PM +0200, Daniel Vetter wrote: > On arm that doesn't work. The iommu api seems like a good fit, except > the dma-api tends to get in the way a bit (drm/msm apparently has > similar problems like tegra), and if you need contiguous memory > dma_alloc_coherent is the

Re: noveau vs arm dma ops

On Wed, Apr 25, 2018 at 08:33:12AM -0700, Christoph Hellwig wrote: > On Wed, Apr 25, 2018 at 12:04:29PM +0200, Daniel Vetter wrote: > > - dma api hides the cache flushing requirements from us. GPUs love > > non-snooped access, and worse give userspace control over that. We want > > a strict

Re: noveau vs arm dma ops

On Wed, Apr 25, 2018 at 5:33 PM, Christoph Hellwig wrote: > On Wed, Apr 25, 2018 at 12:04:29PM +0200, Daniel Vetter wrote: >> > Coordinating the backport of a trivial helper in the arm tree is not >> > the end of the world. Really, this cowboy attitude is a good reason >> >

Re: noveau vs arm dma ops

On Wed, Apr 25, 2018 at 12:04:29PM +0200, Daniel Vetter wrote: > > Coordinating the backport of a trivial helper in the arm tree is not > > the end of the world. Really, this cowboy attitude is a good reason > > why graphics folks have such a bad rep. You keep poking into random > > kernel

Re: noveau vs arm dma ops

On Wed, Apr 25, 2018 at 01:54:39AM -0700, Christoph Hellwig wrote: > [discussion about this patch, which should have been cced to the iommu > and linux-arm-kernel lists, but wasn't: > https://www.spinics.net/lists/dri-devel/msg173630.html] > > On Wed, Apr 25, 2018 at 09:41:51AM +0200, Thierry

Re: noveau vs arm dma ops

On Wed, Apr 25, 2018 at 01:54:39AM -0700, Christoph Hellwig wrote: > [discussion about this patch, which should have been cced to the iommu > and linux-arm-kernel lists, but wasn't: > https://www.spinics.net/lists/dri-devel/msg173630.html] > > On Wed, Apr 25, 2018 at 09:41:51AM +0200, Thierry

noveau vs arm dma ops

[discussion about this patch, which should have been cced to the iommu and linux-arm-kernel lists, but wasn't: https://www.spinics.net/lists/dri-devel/msg173630.html] On Wed, Apr 25, 2018 at 09:41:51AM +0200, Thierry Reding wrote: > > API from the iommu/dma-mapping code. Drivers have no