Re: [PATCH 1/3] dt-bindings: mmc: mmci: add a property to disable DMA LLI

Yann Gautier
2022-03-28T15:00:43Z

On 3/25/22 21:12, Linus Walleij wrote:
> On Tue, Mar 15, 2022 at 9:26 AM Yann Gautier <yann.gautier@foss.st.com> wrote:
>
>> 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?
>
Hi Linus,

> Would it not be better if the bounce buffer is something available
> for all MMCI variants and not restricted to the STM32 DMA add-on?

The issue was seen with the internal DMA of the STM32 variant of PL180.

>
> What I'm thinking is that this is a problem with the MMCI hardware
> rather than with the DMA hardware, so the problem kind of gets
> fixed in the wrong place if the bounce buffer is in the DMA add-on
> code.
>
> Maybe this is how you fixed it in later patches, I'll take a look.

I've pushed a new version there to correct latest remarks from Ulf:
https://lore.kernel.org/all/20220328145114.334577-1-yann.gautier@foss.st.com/

>
> Yours,
> Linus Walleij

Best regards,
Yann