linux-kernel - Re: [PATCH 4/4] mmc: sdhci-esdhc-imx: Remove the ENGcm07207 workaround

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Message-ID: <CAOMZO5AONaJOeGB4qBEfMtS2LGL45FuhAtGQhME4thyiwaPUvg@mail.gmail.com>
Date:   Mon, 29 May 2017 08:14:48 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Benoît Thébaudeau <benoit@...stem.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Fabio Estevam <fabio.estevam@....com>,
        joancarles <joancarles@...ngenieria.es>,
        Eric Bénard <eric@...rea.com>,
        Wolfram Sang <wsa@...-dreams.de>
Subject: Re: [PATCH 4/4] mmc: sdhci-esdhc-imx: Remove the ENGcm07207 workaround

On Wed, May 3, 2017 at 7:05 AM, Benoît Thébaudeau <benoit@...stem.com> wrote:
> The SDHCI_QUIRK_NO_MULTIBLOCK quirk was used as a workaround for the
> ENGcm07207 erratum. However, it caused excruciatingly slow SD transfers
> (300 kB/s on average), and this erratum actually does not imply that
> multiple-block transfers are not supported, so this was overkill.
>
> The suggested workaround for this erratum is to set SYSCTL.RSTA, but the
> simple DAT line software reset (which resets the DMA circuit among
> others) triggered by sdhci_finish_data() in case of errors seems to be
> sufficient. Indeed, generating errors in a controlled manner on i.MX25
> using the FEVT register right in the middle of read data transfers
> without this quirk shows that nothing is written to the buffer by the
> eSDHC past CMD12, and no extra Auto CMD12 is sent with AC12EN set, so
> the data transfers on AHB are properly aborted. For write data
> transfers, neither extra data nor extra Auto CMD12 is sent, as expected.
> Moreover, after intensive stress tests on i.MX25, removing
> SDHCI_QUIRK_NO_MULTIBLOCK seems to be safe.
>
> Signed-off-by: Benoît Thébaudeau <benoit@...stem.com>

Reviewed-by: Fabio Estevam <fabio.estevam@....com>