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Thu, 17 Mar 2022 11:18:00 +0100 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id AFA8910002A; Thu, 17 Mar 2022 11:17:58 +0100 (CET) Received: from Webmail-eu.st.com (sfhdag2node2.st.com [10.75.127.5]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 9B821215132; Thu, 17 Mar 2022 11:17:58 +0100 (CET) Received: from [10.211.8.11] (10.75.127.47) by SFHDAG2NODE2.st.com (10.75.127.5) with Microsoft SMTP Server (TLS) id 15.0.1497.26; Thu, 17 Mar 2022 11:17:57 +0100 Message-ID: <6bfade04-36b4-98c3-2796-ebeaa230f52e@foss.st.com> Date: Thu, 17 Mar 2022 11:17:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH 1/3] dt-bindings: mmc: mmci: add a property to disable DMA LLI Content-Language: en-US To: Ulf Hansson CC: Linus Walleij , Rob Herring , , , , , , Alexandre Torgue , Christophe Kerello , Ludovic Barre , Maxime Coquelin , Philipp Zabel , Russell King , Marek Vasut , , Manivannan Sadhasivam , Grzegorz Szymaszek References: <20220304135134.47827-1-yann.gautier@foss.st.com> <20220304135134.47827-2-yann.gautier@foss.st.com> <0bc53018-fce4-4104-fa47-6e60d2367d69@foss.st.com> From: Yann Gautier In-Reply-To: X-Originating-IP: [10.75.127.47] X-ClientProxiedBy: SFHDAG2NODE2.st.com (10.75.127.5) To SFHDAG2NODE2.st.com (10.75.127.5) X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.850,Hydra:6.0.425,FMLib:17.11.64.514 definitions=2022-03-17_03,2022-03-15_01,2022-02-23_01 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220317_031835_515877_0C50A901 X-CRM114-Status: GOOD ( 27.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 3/17/22 11:00, Ulf Hansson wrote: > On Tue, 15 Mar 2022 at 09:26, Yann Gautier wrote: >> >> On 3/14/22 23:43, Linus Walleij wrote: >>> "On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier wrote: >>> >>>> On STMicroelectronics variant of PL18x, the DMA Linked Lists are supported >>>> starting from revision v2 of the peripheral. But it has limitations, >>>> as all the buffers should be aligned on block size (except the last one). >>>> But this cannot be guaranteed with SDIO. We should then have a property >>>> to disable the support of LLI. >>>> >>>> Signed-off-by: Yann Gautier >>> >>> Actually I think this is present also on the ux500 variants. See: >>> commit 2253ed4b36dc876d1598c4dab5587e537ec68c34 >>> "mmc: mmci: Support any block sizes for ux500v2 and qcom variant" >>> >>> Spot the variant data "dma_power_of_2". >>> >>> So whatever property you add >>> to the variant data (not in the device tree please) should >>> be added to the ux500 variants as well, it will *VERY* likely >>> have a problem with LLI elements not being a power of 2 >>> as it is the ancestor of later STMicro variants. >>> >>> It might actually be the reason for some annoying WiFi error >>> messages I have seen :/ >>> >>> Yours, >>> Linus Walleij >> >> Hi Linus, >> >> The STM32 variant uses an internal DMA, and the DMA functions are in its >> dedicated file. So I was planning to do the same as what is done in >> meson-gx-mmc.c: using a bounce buffer to copy from/to in case DMA >> constraints are not fulfilled. Not sure it can help for Ux500. > Hi Ulf, > We already have a bounce buffer in mmci_pio_read(), but we need one in > mmc_pio_write() too, which hasn't been implemented yet. The idea is to keep using our internal DMA, and not switch to pio mode. > >> >> Ulf, before I send my new series (although it is not ready yet), would >> you be OK with the bounce buffer idea? > > Yes, that works for me. I have patches almost ready, I'll send that soon. > > On the other hand, it would be even better if we could specify the > buffer limitations per mmc host instance, so upper layers (SDIO func > drivers) could conform to these - and use better buffers, to achieve a > better performance. We've seen things that could be improved in the wifi driver. I'll check what could be done. Best regards, Yann > >> >> >> Best regards, >> Yann > > Kind regards > Uffe _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel