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[78.88.45.245]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-615a8f17829sm8316020a12.19.2025.08.05.07.04.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Aug 2025 07:05:05 -0700 (PDT) Message-ID: <96cf6022-ef69-4749-88b0-e18a07bb8427@oss.qualcomm.com> Date: Tue, 5 Aug 2025 16:04:58 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 2/6] dmaengine: Make of_dma_request_slave_channel pass a cookie to of_xlate To: Laurent Pinchart Cc: Frank Li , Konrad Dybcio , Vinod Koul , Sven Peter , Janne Grunau , Alyssa Rosenzweig , Neal Gompa , Ludovic Desroches , Florian Fainelli , Broadcom internal kernel review list , Ray Jui , Scott Branden , Paul Cercueil , Eugeniy Paltsev , Viresh Kumar , Andy Shevchenko , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Taichi Sugaya , Takao Orito , =?UTF-8?Q?Andreas_F=C3=A4rber?= , Manivannan Sadhasivam , Daniel Mack , Haojian Zhuang , Robert Jarzmik , Geert Uytterhoeven , Magnus Damm , Patrice Chotard , Linus Walleij , =?UTF-8?Q?Am=C3=A9lie_Delaunay?= , Maxime Coquelin , Alexandre Torgue , Chen-Yu Tsai , Jernej Skrabec , Samuel Holland , Laxman Dewangan , Jon Hunter , Thierry Reding , Peter Ujfalusi , Kunihiko Hayashi , Masami Hiramatsu , Michal Simek , Rob Herring , Saravana Kannan , =?UTF-8?Q?Martin_Povi=C5=A1er?= , Liam Girdwood , Mark Brown , Jaroslav Kysela , Takashi Iwai , Kuninori Morimoto , Mukesh Kumar Savaliya , Viken Dadhaniya , Andi Shyti , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Marijn Suijten , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-rpi-kernel@lists.infradead.org, linux-mips@vger.kernel.org, imx@lists.linux.dev, linux-actions@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-sunxi@lists.linux.dev, linux-tegra@vger.kernel.org, devicetree@vger.kernel.org, linux-sound@vger.kernel.org, linux-i2c@vger.kernel.org, linux-spi@vger.kernel.org References: <20250730-topic-dma_genise_cookie-v1-0-b505c1238f9f@oss.qualcomm.com> <20250730-topic-dma_genise_cookie-v1-2-b505c1238f9f@oss.qualcomm.com> <20250730180417.GC21430@pendragon.ideasonboard.com> <20250801120007.GB4906@pendragon.ideasonboard.com> <0c2cc631-21fd-41fd-9293-fd86dd09a2d2@oss.qualcomm.com> <20250804235140.GB12087@pendragon.ideasonboard.com> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <20250804235140.GB12087@pendragon.ideasonboard.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: cpF3LAbIoCS076Fhh4PeWE50dkYj4l5G X-Authority-Analysis: v=2.4 cv=F/xXdrhN c=1 sm=1 tr=0 ts=68920f95 cx=c_pps a=HLyN3IcIa5EE8TELMZ618Q==:117 a=FpWmc02/iXfjRdCD7H54yg==:17 a=IkcTkHD0fZMA:10 a=2OwXVqhp2XgA:10 a=EUspDBNiAAAA:8 a=IUwAV-ZVHCOG9dU_XxAA:9 a=QEXdDO2ut3YA:10 a=bTQJ7kPSJx9SKPbeHEYW:22 X-Proofpoint-ORIG-GUID: cpF3LAbIoCS076Fhh4PeWE50dkYj4l5G X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODA1MDEwMiBTYWx0ZWRfXz44MPLOsSJoc lZieEXUg38faLszru6f3DjWbAOIbdzgVIq/dgkT2U0q9ygKjOmrywXPWP6BuYTPNrVN6KPhm10k ffsFygjfWpEL97X5EmiRF7acz/TeRDYaxz3TnuKJeaq4dRN/ttbwgNYJNkzgkhk3j1Kyl75BTfw JT8y14jj21sDzXZa/Ni9AWK2W3ds6sRwdmZS5rmNTR0ux3RvNNyiMmiS0+dENW7mjmlkDCGbSvA lXVtKK6W/LjSzpL6MHQJOkEWmjFI2FLSMJerxZaYJjkDNMHQao7gMHHYYHHqhXMMWstHB6UGWtA N3qr2xonycpaTTgCROn8inystdXXW7FCEz0PUUfPNI18KH2TP+nKJL8w4sTOVAlVO1MB1+LCUKi EFELhR0V1X599JWj+QlO57hwHOg0Zg9agnnyPsvuOtsUuM5teLWgF2OUqxjhGhnqVpLs0BoT X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-05_04,2025-08-04_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 mlxscore=0 phishscore=0 bulkscore=0 adultscore=0 clxscore=1015 mlxlogscore=999 priorityscore=1501 impostorscore=0 malwarescore=0 lowpriorityscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2508050102 On 8/5/25 1:51 AM, Laurent Pinchart wrote: > On Sat, Aug 02, 2025 at 02:37:54PM +0200, Konrad Dybcio wrote: >> On 8/1/25 2:00 PM, Laurent Pinchart wrote: >>> On Wed, Jul 30, 2025 at 02:37:54PM -0400, Frank Li wrote: >>>> On Wed, Jul 30, 2025 at 09:04:17PM +0300, Laurent Pinchart wrote: >>>>> On Wed, Jul 30, 2025 at 12:39:43PM -0400, Frank Li wrote: >>>>>> On Wed, Jul 30, 2025 at 11:33:29AM +0200, Konrad Dybcio wrote: >>>>>>> From: Konrad Dybcio >>>>>>> >>>>>>> The DMA subsystem attempts to make it theoretically possible to pair >>>>>>> any DMA block with any user. While that's convenient from a >>>>>>> codebase sanity perspective, some blocks are more intertwined. >>>>>>> >>>>>>> One such case is the Qualcomm GENI, where each wrapper contains a >>>>>>> number of Serial Engine instances, each one of which can be programmed >>>>>>> to support a different protocol (such as I2C, I3C, SPI, UART, etc.). >>>>>>> >>>>>>> The GPI DMA it's designed together with, needs to receive the ID of the >>>>>>> protocol that's in use, to adjust its behavior accordingly. Currently, >>>>>>> that's done through passing that ID through device tree, with each >>>>>>> Serial Engine expressed NUM_PROTOCOL times, resulting in terrible >>>>>>> dt-bindings that are full of useless copypasta. >>>>>>> >>>>>>> In a step to cut down on that, let the DMA user give the engine driver >>>>>>> a hint at request time. >>>>>>> >>>>>>> Signed-off-by: Konrad Dybcio >>>>>>> --- [...] >> So.. do you folks want me to alter the patch in any way? > > I think the runtime PM issue is orthogonal to the problem this series > addresses. It can be addressed separately. > > That being said, I'm not a big fan of passing a void pointer to > .of_xlate() to carry device-specific information, in a device-specific > format. This seems prone to mismatch between clients and DMA engines. > .of_xlate() also seems the wrong place to do this. It would be cleaner > if we could use another operation, such as dmaengine_slave_config() for > instance. Right, I noticed that the drivers in question already apparently do the very same thing (passing data through a voidptr), inside slave_config (via the peripheral_config/_size fields).. But that doesn't solve the issue this series is trying to tackle, since every DMA consumer driver passes its own structure (or NULL). My immediate idea is to add yet another field, but that's lame. The other immediate idea would be to put an `u8 variant` at the start of all of these structs ("we have tagged enums at home"), but that's lame *and* dangerous. Ideas? Konrad