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[95.217.157.248]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-543c8381772sm1375919e87.249.2025.01.27.11.35.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Jan 2025 11:35:05 -0800 (PST) References: <20250115-b4-rkisp-noncoherent-v2-0-0853e1a24012@gmail.com> <20250115-b4-rkisp-noncoherent-v2-1-0853e1a24012@gmail.com> User-agent: mu4e 1.10.9; emacs 29.4.50 From: Mikhail Rudenko To: Tomasz Figa Cc: Dafna Hirschfeld , Laurent Pinchart , Mauro Carvalho Chehab , Heiko Stuebner , Marek Szyprowski , Hans Verkuil , Sergey Senozhatsky , linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Mauro Carvalho Chehab , stable@vger.kernel.org Subject: Re: [PATCH v2 1/2] media: videobuf2: Fix dmabuf cache sync/flush in dma-contig Date: Mon, 27 Jan 2025 22:25:51 +0300 In-reply-to: Message-ID: <87jzag82zd.fsf@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi Tomasz, and thanks for your review! On 2025-01-27 at 20:18 +09, Tomasz Figa wrote: > Hi Mikhail, > > On Thu, Jan 16, 2025 at 2:25=E2=80=AFAM Mikhail Rudenko wrote: >> >> When support for V4L2_FLAG_MEMORY_NON_CONSISTENT was removed in >> commit 129134e5415d ("media: media/v4l2: remove >> V4L2_FLAG_MEMORY_NON_CONSISTENT flag"), >> vb2_dc_dmabuf_ops_{begin,end}_cpu_access() functions were made >> no-ops. Later, when support for V4L2_MEMORY_FLAG_NON_COHERENT was >> introduced in commit c0acf9cfeee0 ("media: videobuf2: handle >> V4L2_MEMORY_FLAG_NON_COHERENT flag"), the above functions remained >> no-ops, making cache maintenance for non-coherent dmabufs allocated by >> dma-contig impossible. >> >> Fix this by reintroducing dma_sync_sg_for_{cpu,device} calls to >> vb2_dc_dmabuf_ops_{begin,end}_cpu_access() functions for non-coherent >> buffers. >> >> Fixes: c0acf9cfeee0 ("media: videobuf2: handle V4L2_MEMORY_FLAG_NON_COHE= RENT flag") >> Cc: stable@vger.kernel.org >> Signed-off-by: Mikhail Rudenko >> --- >> drivers/media/common/videobuf2/videobuf2-dma-contig.c | 14 ++++++++++++= ++ >> 1 file changed, 14 insertions(+) >> > > Thanks a lot for the patch! > Sorry, for the delay. Ended up being sick with some nasty cold that > took quite a while to recover. > Please take a look at my comments inline. > >> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/dri= vers/media/common/videobuf2/videobuf2-dma-contig.c >> index bb0b7fa67b539aa73ad5ccf3c3bc318e26f8a4cb..889d6c11e15ab5cd4b4c317e= 865f1fef92df4b66 100644 >> --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c >> +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c >> @@ -427,6 +427,13 @@ static int >> vb2_dc_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf, >> enum dma_data_direction direction) >> { >> + struct vb2_dc_buf *buf =3D dbuf->priv; >> + struct sg_table *sgt =3D buf->dma_sgt; >> + >> + if (!buf->non_coherent_mem || buf->vb->skip_cache_sync_on_finish) > > skip_cache_sync_on_finish shouldn't apply to this function, because > the buffer was shared with an external DMA-buf importer and we don't > know in what state it is at this point. > Ack, will fix in v3. >> + return 0; >> + > > We should also take care of the kernel mapping if it exists, because > on some platforms it may not be coherent with the userspace one - > using flush_kernel_vmap_range(). Please check how > vb2_dc_prepare()/vb2_dc_finish() do it. > Thanks for the pointer, will do so in v3. >> + dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir= ); > > We can use the dma_sync_sgtable_*() variant here so we can just pass > the entire sgt to it. > Will do so. >> return 0; >> } >> >> @@ -434,6 +441,13 @@ static int >> vb2_dc_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf, >> enum dma_data_direction direction) >> { >> + struct vb2_dc_buf *buf =3D dbuf->priv; >> + struct sg_table *sgt =3D buf->dma_sgt; >> + >> + if (!buf->non_coherent_mem || buf->vb->skip_cache_sync_on_prepar= e) >> + return 0; >> + >> + dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_= dir); >> return 0; > > Overall the same comments here as for > vb2_dc_dmabuf_ops_begin_cpu_access() +/- flush would change to > invalidate. Ack. > Best regards, > Tomasz -- Best regards, Mikhail Rudenko