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[209.85.222.177]) by smtp.gmail.com with ESMTPSA id l16-20020ac848d0000000b0041514d1da65sm2273558qtr.20.2023.09.12.00.52.02 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 Sep 2023 00:52:03 -0700 (PDT) Received: by mail-qk1-f177.google.com with SMTP id af79cd13be357-76f17eab34eso323076485a.0 for ; Tue, 12 Sep 2023 00:52:02 -0700 (PDT) X-Received: by 2002:a05:620a:a1c:b0:76f:93e:4b45 with SMTP id i28-20020a05620a0a1c00b0076f093e4b45mr11888873qka.69.1694505122529; Tue, 12 Sep 2023 00:52:02 -0700 (PDT) MIME-Version: 1.0 References: <20230828075420.2009568-1-anle.pan@nxp.com> In-Reply-To: From: Tomasz Figa Date: Tue, 12 Sep 2023 16:51:43 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [EXT] Re: [PATCH] media: videobuf2-dma-sg: limit the sg segment size To: Hui Fang Cc: Anle Pan , "m.szyprowski@samsung.com" , "mchehab@kernel.org" , "linux-media@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Jindong Yue , Xuegang Liu , Xu Yang Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (agentk.vger.email [0.0.0.0]); Tue, 12 Sep 2023 00:52:45 -0700 (PDT) X-Spam-Status: No, score=-2.0 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on agentk.vger.email On Tue, Sep 12, 2023 at 4:43=E2=80=AFPM Hui Fang wrote: > > On Tue, Sep 12, 2023 at 4:11=E2=80=AFPM Tomasz Figa = wrote: > > Is your DMA device restricted only to the bottom-most 4 GB (32-bit DMA > > address)? If yes, would it make sense to also allocate from that area r= ather > > than bouncing the memory? > > The DMA device use 32-bit DMA address. > From user space, can't control the v4l2 buffer address, may still change = the > code of vb2_dma_sg_alloc(). Right. You may want to try modifying vb2_dma_sg_alloc_compacted() to use dma_alloc_pages() instead of alloc_pages(). Best regards, Tomasz