RE: [PATCH] sdhci-esdhc-imx: fix bus-width for 1-bit operation.

[Bough Chen]

+Aisheng.

Best Regards
Haibo Chen

> -----Original Message-----
> From: linux-mmc-owner@xxxxxxxxxxxxxxx [mailto:linux-mmc-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Leonardo G. Veiga
> Sent: Tuesday, November 01, 2016 11:58 PM
> To: ulf.hansson@xxxxxxxxxx
> Cc: linux-mmc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> stefan@xxxxxxxx; raul.munoz@xxxxxxxxxxx; leonardo.veiga@xxxxxxxxxxx
> Subject: [PATCH] sdhci-esdhc-imx: fix bus-width for 1-bit operation.
> 
> From: Leonardo Graboski Veiga <leonardo.veiga@xxxxxxxxxxx>
> 
> The 1-bit operation mode, enabled by seeting the 'bus-width' property of the
> device tree 'esdhc' node to <1>, not work while using SD card.
> 
> The behavior is only noticed when only the data pin 0 is connected to the
> hardware. A series of kernel errors are printed to the console, all of them
> returning the following error message followed by some explanation:
> mmcblk0: error -84 transferring data
> 
> If four data lines are connected, it ignores the device-tree property and works
> in 4-bit mode of operation without errors. The hardware used for testing does
> not support 8-bit mode.
> 
> Check the 'bus-width' property and if set to <1>, enable the
> SDHCI_QUIRK_FORCE_1_BIT_DATA quirk.
> 
> Signed-off-by: Leonardo Graboski Veiga <leonardo.veiga@xxxxxxxxxxx>
> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-
> esdhc-imx.c
> index c9fbc4c3..88d7d22 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -1003,6 +1003,10 @@ sdhci_esdhc_imx_probe_dt(struct platform_device
> *pdev,
>  		host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V;
>  	}
> 
> +	if (!of_property_read_u32(np, "bus-width", &boarddata-
> >max_bus_width)
> +		&& boarddata->max_bus_width == 1)
> +		host->quirks |= SDHCI_QUIRK_FORCE_1_BIT_DATA;
> +
>  	/* call to generic mmc_of_parse to support additional capabilities */
>  	ret = mmc_of_parse(host->mmc);
>  	if (ret)
> --
> 2.7.4
> 
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