Hi Leonardo,
On Tue, Nov 1, 2016 at 11:58 PM, Leonardo G. Veiga <leogveiga@xxxxxxxxx> wrote:
> 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;
> +
This looks like a common SDHCI driver issue that it assumes the default
bus-width as 4 bit if no SDHCI_QUIRK_FORCE_1_BIT_DATA specified.
if (!(host->quirks & SDHCI_QUIRK_FORCE_1_BIT_DATA))
mmc->caps |= MMC_CAP_4_BIT_DATA;
And I'm not sure Andrian or Ulf would like to see people keep using this quirk.
IMHO we probably could totally remove it since bus-width already tells
what the driver needs.
Andrian & Ulf,
Comments?
> /* call to generic mmc_of_parse to support additional capabilities */
> ret = mmc_of_parse(host->mmc);
> if (ret)
> --
> 2.7.4
>
Regards
Dong Aisheng
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