From: Vivek Gautam <vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> To: Rob Clark <robdclark-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Cc: David Airlie <airlied-cv59FeDIM0c@public.gmane.org>, linux-arm-msm <linux-arm-msm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, open list <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, dri-devel <dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>, Tomasz Figa <tfiga-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>, hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, Jordan Crouse <jcrouse-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>, Sean Paul <seanpaul-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>, freedreno <freedreno-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org> Subject: Re: [PATCH v2 1/1] drm: msm: Replace dma_map_sg with dma_sync_sg* Date: Thu, 29 Nov 2018 15:14:21 +0530 [thread overview] Message-ID: <CAFp+6iFDanGLoWf95CR2Etq76tC8+dpciOcJzou4QfAUO3WRQA@mail.gmail.com> (raw) In-Reply-To: <CAF6AEGuM-R0=KRSmT+bt6SBaZg_ea3A_YFE+xfR_oCH9d9uORA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> On Wed, Nov 28, 2018 at 6:09 PM Rob Clark <robdclark@gmail.com> wrote: > > On Wed, Nov 28, 2018 at 2:39 AM Christoph Hellwig <hch@infradead.org> wrote: > > > > > + /* > > > + * dma_sync_sg_*() flush the physical pages, so point > > > + * sg->dma_address to the physical ones for the right behavior. > > > + */ > > > + for_each_sg(msm_obj->sgt->sgl, s, msm_obj->sgt->nents, i) > > > + sg_dma_address(s) = sg_phys(s); > > > + > > > > I'm sorry, but this is completely bogus and not acceptable. > > > > The only place that is allowed to initialize sg_dma_address is > > dma_map_sg. If the default dma ops don't work for your setup we have > > major a problem and need to fix the dma api / iommu integration instead > > of hacking around it. > > I agree that the dma/iommu integration is very problematic for drm (in > particular, gpu drivers that use the iommu as an gpu mmu).. Really we > need a way that a driver can opt-out of this, and access the cpu cache > APIs directly, skipping the dma API entirely. But as it is, we've had > to hack around the dma API. I'm not really sure this hack is any > worse than abusing dma_(un)map_sg() for doing cache operations. > > I probably should have paid more attention and nak'd the dma/iommu > integration before it landed. But given that now we are stuck in this > situation, while I'm certainly interested if anyone has some ideas > about how to let drivers opt out of the dma/iommu integration and > bypass the dma API layer, I'm ok with replacing a hack with a less-bad > hack. May I take it as a positive nod to respin the next version? Regards Vivek > > BR, > -R -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation _______________________________________________ Freedreno mailing list Freedreno@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/freedreno
WARNING: multiple messages have this Message-ID (diff)
From: Vivek Gautam <vivek.gautam@codeaurora.org> To: Rob Clark <robdclark@gmail.com> Cc: hch@infradead.org, David Airlie <airlied@linux.ie>, Tomasz Figa <tfiga@chromium.org>, open list <linux-kernel@vger.kernel.org>, freedreno <freedreno@lists.freedesktop.org>, dri-devel <dri-devel@lists.freedesktop.org>, linux-arm-msm <linux-arm-msm@vger.kernel.org>, Jordan Crouse <jcrouse@codeaurora.org>, Sean Paul <seanpaul@chromium.org> Subject: Re: [PATCH v2 1/1] drm: msm: Replace dma_map_sg with dma_sync_sg* Date: Thu, 29 Nov 2018 15:14:21 +0530 [thread overview] Message-ID: <CAFp+6iFDanGLoWf95CR2Etq76tC8+dpciOcJzou4QfAUO3WRQA@mail.gmail.com> (raw) In-Reply-To: <CAF6AEGuM-R0=KRSmT+bt6SBaZg_ea3A_YFE+xfR_oCH9d9uORA@mail.gmail.com> On Wed, Nov 28, 2018 at 6:09 PM Rob Clark <robdclark@gmail.com> wrote: > > On Wed, Nov 28, 2018 at 2:39 AM Christoph Hellwig <hch@infradead.org> wrote: > > > > > + /* > > > + * dma_sync_sg_*() flush the physical pages, so point > > > + * sg->dma_address to the physical ones for the right behavior. > > > + */ > > > + for_each_sg(msm_obj->sgt->sgl, s, msm_obj->sgt->nents, i) > > > + sg_dma_address(s) = sg_phys(s); > > > + > > > > I'm sorry, but this is completely bogus and not acceptable. > > > > The only place that is allowed to initialize sg_dma_address is > > dma_map_sg. If the default dma ops don't work for your setup we have > > major a problem and need to fix the dma api / iommu integration instead > > of hacking around it. > > I agree that the dma/iommu integration is very problematic for drm (in > particular, gpu drivers that use the iommu as an gpu mmu).. Really we > need a way that a driver can opt-out of this, and access the cpu cache > APIs directly, skipping the dma API entirely. But as it is, we've had > to hack around the dma API. I'm not really sure this hack is any > worse than abusing dma_(un)map_sg() for doing cache operations. > > I probably should have paid more attention and nak'd the dma/iommu > integration before it landed. But given that now we are stuck in this > situation, while I'm certainly interested if anyone has some ideas > about how to let drivers opt out of the dma/iommu integration and > bypass the dma API layer, I'm ok with replacing a hack with a less-bad > hack. May I take it as a positive nod to respin the next version? Regards Vivek > > BR, > -R -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
next prev parent reply other threads:[~2018-11-29 9:44 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-11-26 21:37 [PATCH v2 1/1] drm: msm: Replace dma_map_sg with dma_sync_sg* Vivek Gautam 2018-11-26 21:37 ` Vivek Gautam [not found] ` <20181126213710.3084-1-vivek.gautam-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> 2018-11-28 3:09 ` Tomasz Figa 2018-11-28 3:09 ` Tomasz Figa 2018-11-29 9:43 ` Vivek Gautam 2018-11-28 7:39 ` Christoph Hellwig [not found] ` <20181128073940.GA13072-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> 2018-11-28 9:02 ` Vivek Gautam 2018-11-28 9:02 ` Vivek Gautam 2018-11-28 12:38 ` Rob Clark 2018-11-28 12:38 ` Rob Clark [not found] ` <CAF6AEGuM-R0=KRSmT+bt6SBaZg_ea3A_YFE+xfR_oCH9d9uORA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2018-11-29 9:44 ` Vivek Gautam [this message] 2018-11-29 9:44 ` Vivek Gautam 2018-11-28 14:19 ` Lukas Wunner
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