linux-kernel - Re: [PATCH v2] mmc: dw_mmc: Reset DMA before enabling IDMAC

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Date:	Fri, 17 Oct 2014 17:58:22 +0530
From:	Alim Akhtar <alim.akhtar@...il.com>
To:	Sonny Rao <sonnyrao@...omium.org>
Cc:	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Douglas Anderson <dianders@...omium.org>,
	Eddie Cai <eddie.cai@...k-chips.com>,
	Addy Ke <addy.ke@...k-chips.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] mmc: dw_mmc: Reset DMA before enabling IDMAC

Hi Sonny,

On Thu, Oct 16, 2014 at 10:28 PM, Sonny Rao <sonnyrao@...omium.org> wrote:
> We've already got a reset of DMA after it's done.  Add one before we
> start DMA too.  This fixes a data corruption on Rockchip SoCs which
> will get bad data when doing a DMA transfer after doing a PIO transfer.
>
> We tested this on an Exynos 5800 with HS200 and didn't notice any
> difference in sequential read throughput.
>
> Signed-off-by: Sonny Rao <sonnyrao@...omium.org>
> Signed-off-by: Doug Anderson <dianders@...omium.org>
> Tested-by: Doug Anderson <dianders@...omium.org>

This looks fine.

Reviewed-by: Alim Akhtar <alim.akhtar@...sung.com>
> ---
>  drivers/mmc/host/dw_mmc.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 69f0cc6..ca67f69 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -83,6 +83,7 @@ struct idmac_desc {
>  #endif /* CONFIG_MMC_DW_IDMAC */
>
>  static bool dw_mci_reset(struct dw_mci *host);
> +static bool dw_mci_ctrl_reset(struct dw_mci *host, u32 reset);
>
>  #if defined(CONFIG_DEBUG_FS)
>  static int dw_mci_req_show(struct seq_file *s, void *v)
> @@ -448,6 +449,10 @@ static void dw_mci_idmac_start_dma(struct dw_mci *host, unsigned int sg_len)
>
>         dw_mci_translate_sglist(host, host->data, sg_len);
>
> +       /* Make sure to reset DMA in case we did PIO before this */
> +       dw_mci_ctrl_reset(host, SDMMC_CTRL_DMA_RESET);
> +       dw_mci_idmac_reset(host);
> +
>         /* Select IDMAC interface */
>         temp = mci_readl(host, CTRL);
>         temp |= SDMMC_CTRL_USE_IDMAC;
> --
> 2.1.2
>



-- 
Regards,
Alim
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