Messages in this thread | | | Date | Tue, 15 Mar 2022 09:26:01 +0100 | Subject | Re: [PATCH 1/3] dt-bindings: mmc: mmci: add a property to disable DMA LLI | From | Yann Gautier <> |
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On 3/14/22 23:43, Linus Walleij wrote: > "On Fri, Mar 4, 2022 at 2:52 PM Yann Gautier <yann.gautier@foss.st.com> 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 <yann.gautier@foss.st.com> > > 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.
Ulf, before I send my new series (although it is not ready yet), would you be OK with the bounce buffer idea?
Best regards, Yann
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