linux-kernel - Re: [PATCH 4/4] mmc: mmci: add hs200 support for stm32 sdmmc

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Date:   Thu, 16 Dec 2021 11:15:22 +0100
From:   Marek Vasut <marex@...x.de>
To:     Yann Gautier <yann.gautier@...s.st.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Russell King <linux@...linux.org.uk>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vladimir Zapolskiy <vz@...ia.com>,
        u.kleine-koenig@...gutronix.de,
        Christophe Kerello <christophe.kerello@...s.st.com>,
        Ludovic Barre <ludovic.barre@...s.st.com>,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/4] mmc: mmci: add hs200 support for stm32 sdmmc

On 12/16/21 10:44, Yann Gautier wrote:
> On 12/16/21 10:14 AM, Marek Vasut wrote:
>> On 12/15/21 15:17, Yann Gautier wrote:
>>> Use feedback clock for HS200 mode, as for SDR104.
>>> The HS200 mode can be enabled through DT by using mmc-hs200-1_8v.
>>> It is possible to use it on STM32MP13, but not STM32MP15 platforms.
>>
>> HS200 is possible even on the MP15, it just doesn't yield any 
>> (performance) benefits due to the slower bus clock (125 MHz or so?), 
>> so it isn't worth enabling it on MP15. It is nice to see MP13 can do 
>> better.
> 
> Hi Marek,
> 
> There is a limitation on MP15, please see errata sheet [1], chapter 2.3.19.
> HS200 (and SDR104) shouldn't be enabled on MP15.
> 
> Best regards,
> Yann
> 
> [1] https://www.st.com/resource/en/errata_sheet/dm00516256.pdf

Oh, I see, so I was lucky to even ever get it working at all.

Thanks for the info.