linux-kernel - Re: [PATCH] mmc: omap_hsmmc: DMA unmap only once in case of MMC error

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Message-ID: <CANfBPZ-azGV0H7asRHD5+vdFjCkrx=E2Oypnrk_SW9K5+DwTLQ@mail.gmail.com>
Date:	Fri, 2 Sep 2011 00:49:21 +0530
From:	"S, Venkatraman" <svenkatr@...com>
To:	Per Forlin <per.forlin@...aro.org>
Cc:	linaro-dev@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Santosh <santosh.shilimkar@...com>,
	Balaji T Krishnamoorthy <balajitk@...com>,
	Sourav Poddar <sourav.poddar@...com>,
	Chris Ball <cjb@...top.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>
Subject: Re: [PATCH] mmc: omap_hsmmc: DMA unmap only once in case of MMC error

On Mon, Aug 29, 2011 at 3:38 AM, Per Forlin <per.forlin@...aro.org> wrote:
> Reported by Russell King:
> ------------
> mmcblk0: error -84 transferring data, sector 149201, nr 64,
> cmd response 0x900, card status 0xb00
> mmcblk0: retrying using single block read
>
> WARNING: at /home/rmk/git/linux-2.6-rmk/lib/dma-debug.c:811 check_unmap
> omap_hsmmc omap_hsmmc.0: DMA-API: device driver tries to free DMA memory
> it has not allocated [device address=0x0000000080933000] [size=20480 bytes]
> -------------
>
> In case of an error dma_unmap() is issued in omap_hsmmc_dma_cleanup()
> and then again in omap_hsmmc_post_req(). Resolve this by clearing the
> host_cookie to indicate there is no DMA mapped memory to unmap.
>
> Signed-off-by: Per Forlin <per.forlin@...aro.org>
> ---
> Bug fix on 3.1-rc3
>
>  drivers/mmc/host/omap_hsmmc.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
> index 21e4a79..31d9817 100644
> --- a/drivers/mmc/host/omap_hsmmc.c
> +++ b/drivers/mmc/host/omap_hsmmc.c
> @@ -1011,6 +1011,7 @@ static void omap_hsmmc_dma_cleanup(struct omap_hsmmc_host *host, int errno)
>                        host->data->sg_len,
>                        omap_hsmmc_get_dma_dir(host, host->data));
>                omap_free_dma(dma_ch);
> +               host->data->host_cookie = 0;
>        }
>        host->data = NULL;
>  }
> @@ -1576,8 +1577,10 @@ static void omap_hsmmc_post_req(struct mmc_host *mmc, struct mmc_request *mrq,
>        struct mmc_data *data = mrq->data;
>
>        if (host->use_dma) {
> -               dma_unmap_sg(mmc_dev(host->mmc), data->sg, data->sg_len,
> -                            omap_hsmmc_get_dma_dir(host, data));
> +               if (data->host_cookie)
> +                       dma_unmap_sg(mmc_dev(host->mmc), data->sg,
> +                                    data->sg_len,
> +                                    omap_hsmmc_get_dma_dir(host, data));
>                data->host_cookie = 0;
>        }
>  }
> --
> 1.7.4.1
>
>

I just posted a patch [1] which just consolidates all unmapping to
just post_req.
This would obviously prevent double unmapping, and keeps all the related
dma operations at a single place. Let me know if that works better.

[1]: http://marc.info/?l=linux-mmc&m=131490406920616&w=2
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