linux-kernel - Re: [PATCH v2] MMC:mmc_spi: Recover from CRC error for SD read/write operation over SPI.

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Message-ID: <AANLkTimwi7IuKZySIkDjlgBi7NDkIaW79CHNbhliJ2UY@mail.gmail.com>
Date:	Fri, 16 Jul 2010 18:51:40 +0800
From:	Sonic Zhang <sonic.adi@...il.com>
To:	David Brownell <dbrownell@...rs.sourceforge.net>
Cc:	linux-mmc@...r.kernel.org,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	uclinux-dist-devel <uclinux-dist-devel@...ckfin.uclinux.org>
Subject: Re: [PATCH v2] MMC:mmc_spi: Recover from CRC error for SD read/write 
	operation over SPI.

Any comments?


Sonic

On Mon, Jul 12, 2010 at 3:50 PM, sonic zhang <sonic.adi@...il.com> wrote:
> >From 94d1ea57ac2fbe37133e25e99ccb265250f0027d Mon Sep 17 00:00:00 2001
> From: Sonic Zhang <sonic.zhang@...log.com>
> Date: Fri, 9 Jul 2010 15:36:20 +0800
> Subject: [PATCH v2] MMC:mmc_spi: Recover from crc error for SD read/write operation over SPI.
>
> SPI bus is not reliable on all platforms when doing large data transfer.
> Current mmc spi driver fails SD read/write command immediately, if
> occasional CRC error is reported by SD device. This patch makes the
> operation recover from the CRC error by doing last SD command again.
> The retry count is set to 5 to ensure the driver pass any stress test.
>
> Signed-off-by: Sonic Zhang <sonic.zhang@...log.com>
> ---
>  drivers/mmc/host/mmc_spi.c |   22 ++++++++++++++++++++++
>  1 files changed, 22 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c
> index ad847a2..8192434 100644
> --- a/drivers/mmc/host/mmc_spi.c
> +++ b/drivers/mmc/host/mmc_spi.c
> @@ -1055,6 +1055,8 @@ static void mmc_spi_request(struct mmc_host *mmc, struct mmc_request *mrq)
>  {
>        struct mmc_spi_host     *host = mmc_priv(mmc);
>        int                     status = -EINVAL;
> +       int                     crc_retry = 5;
> +       struct mmc_command      stop;
>
>  #ifdef DEBUG
>        /* MMC core and layered drivers *MUST* issue SPI-aware commands */
> @@ -1084,10 +1086,30 @@ static void mmc_spi_request(struct mmc_host *mmc, struct mmc_request *mrq)
>        }
>  #endif
>
> +crc_recover:
>        /* issue command; then optionally data and stop */
>        status = mmc_spi_command_send(host, mrq, mrq->cmd, mrq->data != NULL);
>        if (status == 0 && mrq->data) {
>                mmc_spi_data_do(host, mrq->cmd, mrq->data, mrq->data->blksz);
> +
> +               /*
> +                * SPI bus is not reliable when doing large data transfer.
> +                * If occasional crc error is reported by SD device when do
> +                * data read/write over SPI, it can be recovered by doing
> +                * last SD command again. The retry count is set to 5 to
> +                * ensure the driver pass any stress test.
> +                */
> +               if (mrq->data->error == -EILSEQ && crc_retry) {
> +                       stop.opcode = MMC_STOP_TRANSMISSION;
> +                       stop.arg = 0;
> +                       stop.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
> +
> +                       status = mmc_spi_command_send(host, mrq, &stop, 0);
> +                       crc_retry--;
> +                       mrq->data->error = 0;
> +                       goto crc_recover;
> +               }
> +
>                if (mrq->stop)
>                        status = mmc_spi_command_send(host, mrq, mrq->stop, 0);
>                else
> --
> 1.6.0
>
>
>
> --
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