On 2016-11-02 01:42, Dong Aisheng wrote: > 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. Hm, I see what you are saying, the problem is that the core (sdhci_setup_host) falls back to 4-bit if SDHCI_QUIRK_FORCE_1_BIT_DATA is not set... Removing that should be fine for DT enabled SDHC drivers, since mmc_of_parse sets MMC_CAP_4_BIT_DATA. But not sure about drivers which parse dt on their own or still support platform data.... Those might rely on MMC_CAP_4_BIT_DATA being set by default... -- Stefan > > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
