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Mon, 14 Sep 2026 22:12:54 -0700 (PDT) X-Received: by 2002:a17:90b:4b10:b0:39b:92bb:9eef with SMTP id 98e67ed59e1d1-39dec0f738cmr10877396a91.22.1789449173407; Mon, 14 Sep 2026 22:12:53 -0700 (PDT) Received: from [10.218.7.127] ([202.46.22.19]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1438d1381c2sm3755853c88.10.2026.09.14.22.12.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Sep 2026 22:12:47 -0700 (PDT) Message-ID: <90fcc9ff-4ba6-4e16-a322-17ad8e4a51e7@oss.qualcomm.com> Date: Tue, 15 Sep 2026 10:42:39 +0530 Precedence: bulk X-Mailing-List: dmaengine@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/5] PCI: epf-mhi: Add batched DMA read support To: Manivannan Sadhasivam , Frank Li Cc: Vinod Koul , Frank Li , Jonathan Corbet , Shuah Khan , Jeff Hugo , =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= , Kishon Vijay Abraham I , Bjorn Helgaas , dmaengine@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, mhi@lists.linux.dev, linux-arm-msm@vger.kernel.org, linux-pci@vger.kernel.org References: <20260803-dma_multi_sg-v2-0-c12bb05e42d6@oss.qualcomm.com> <20260803-dma_multi_sg-v2-4-c12bb05e42d6@oss.qualcomm.com> Content-Language: en-US From: Sumit Kumar In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Authority-Analysis: v=2.4 cv=G+KJgNk5 c=1 sm=1 tr=0 ts=6aa8d3d8 cx=c_pps a=0uOsjrqzRL749jD1oC5vDA==:117 a=fChuTYTh2wq5r3m49p7fHw==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=gowsoOTTUOVcmtlkKump:22 a=Z1hDqqN1xTHES3mYk24A:9 a=QEXdDO2ut3YA:10 a=mQ_c8vxmzFEMiUWkPHU9:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTE1MDA3MSBTYWx0ZWRfXym6TGykcp5fv DsysvH+zOH4cH+mjwjIW4aosz0AklxyU+CKvt36PVO8mI1AxWoJfW0ShQF5TJUHIguwy5jEIxiV GfpOKif90vU/rf9BhDb5BOrzXD/vjcgx8SCt+r9GLTkof1OviZc1SrrdtKs5YZ20zjBucZG4w+m 1/RJEzJR0jm2uD5aYWtQSGJJPWyL9rlrTAcfttdZYTtk6qksNftTQwszcr2Vuqch229eyZvxXZK oToGJ9KIFip6vanYArMDFJ5WRXLCgrfEWvFcQ3323VPpy0l009BzGmsnJoEcNQyQmPIO6wOVTJM 42Zu5Q1m5KjidD8BDVIp6+5LncKbDjGR5g369sjBNvzJDDE5omQp8Ap4MvjUVGjhiz10RNBV/qo 1UfbmTSqbwvOLYPlxS5Cm7/CuC2lpp3NIxguNn9IQWbBFsgw7U6TK6rYRD++bk3QnQUpQAGxo7e KlEcrtDaTx07cAeWmXA== X-Proofpoint-GUID: 7_nabYBRz6CY2lTl1wSWoqjnD82BLN2V X-Proofpoint-ORIG-GUID: 7_nabYBRz6CY2lTl1wSWoqjnD82BLN2V X-Proofpoint-Spam-Info: AW1haW4tMjYwOTE1MDA3MSBTYWx0ZWRfX+Cq5m3EAHzpg OqFq6F25NtvZxhemPA67KaA3dHKYSTA7eKjZDW//73ko1HEBgHRrfYCjGhkadR5uKqQ+y3P7HR3 V1JfPzNAHxjm5e4ljfIkpi41z5o+M+o= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-15_01,2026-09-14_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 bulkscore=0 impostorscore=0 malwarescore=0 clxscore=1015 lowpriorityscore=0 phishscore=0 adultscore=0 priorityscore=1501 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609150071 On 8/14/2026 8:22 PM, Manivannan Sadhasivam wrote: > On Thu, Aug 06, 2026 at 12:11:34PM -0500, Frank Li wrote: > > [...] > >>> + config.direction = DMA_DEV_TO_MEM; >>> + ret = dmaengine_slave_config(chan, &config); >>> + if (ret) { >>> + dev_err(dev, "Failed to configure DMA channel for %u-buffer batch read: %d\n", >>> + num_buffers, ret); >>> + goto err_unmap; >>> + } >>> + >>> + desc = dmaengine_prep_dma_sg(chan, dst_sg, num_buffers, >>> + src_sg, num_buffers, >>> + DMA_CTRL_ACK | DMA_PREP_INTERRUPT); >> Although both side memory address, but as previous discussion, which is not >> memcpy, still memory to IO space transfer. >> > I agree, it is peripheral DMA nevertheless. > >> Maybe enhence device_prep_peripheral_dma_vec(). Actually eDMA still split >> it to small trunk and linked together. >> > By enhance you mean keeping the semantics of device_prep_peripheral_dma_vec() > API? I don't know how it helps because we would most likely end up with two > vector arguments and duplicating scatter-gather lists. Frank can you comment on this. > - Mani >