On Fri, Feb 07, 2014 at 03:29:51PM +0000, Russell King - ARM Linux wrote:
> Hi,
>
> I have a Samsung 8GB UHS-1 card which I'm trying with iMX6Q, and it's
> not behaving very well with the voltage switch. With MMC debugging
> enabled - and augmented with additional debug for the ESDHC_VENDOR
> register, I'm seeing this with 3.14-rc1:
>
> [ 2.771270] mmc1: starting CMD11 arg 00000000 flags 00000015
> [ 2.771575] sdhci [sdhci_irq()]: *** mmc1 got interrupt: 0x00000080
> [ 2.771613] sdhci [sdhci_irq()]: *** mmc1 got interrupt: 0x00000001
> [ 2.771632] mmc1: req done (CMD11): 0: 00000320 00000000 00000000 00000000
> [ 2.772669] mmc1: clock 0Hz busmode 2 powermode 2 cs 0 Vdd 21 width 0 timing 0
> [ 2.772679] mmc1: clearing ESDHC_VENDOR_SPEC_FRC_SDCLK_ON
> [ 2.772687] mmc1: ESDHC_VENDOR_SPEC_VSELECT is clear
> [ 2.772695] mmc1: clearing ESDHC_VENDOR_SPEC_VSELECT
> [ 2.772703] mmc1: clearing ESDHC_VENDOR_SPEC_FRC_SDCLK_ON
> [ 2.772713] sdhci-esdhc-imx 2194000.usdhc: change pinctrl state for uhs 0
> [ 2.772719] mmc1: clearing ESDHC_VENDOR_SPEC_FRC_SDCLK_ON
> [ 2.772729] mmc1: ESDHC_VENDOR_SPEC_VSELECT is clear
> [ 2.772735] mmc1: setting ESDHC_VENDOR_SPEC_VSELECT
> [ 2.778276] mmc1: ESDHC_VENDOR_SPEC_VSELECT is sett
> [ 2.786482] mmc1: clock 400000Hz busmode 2 powermode 2 cs 0 Vdd 21 width 0 timing 0
> [ 2.786502] sdhci-esdhc-imx 2194000.usdhc: desired SD clock: 400000, actual: 386718
> [ 2.786511] mmc1: setting ESDHC_VENDOR_SPEC_FRC_SDCLK_ON
> [ 2.787515] mmc1: ESDHC_VENDOR_SPEC_VSELECT is sett
> [ 2.787522] mmc1: setting ESDHC_VENDOR_SPEC_VSELECT
> [ 2.787529] mmc1: clearing ESDHC_VENDOR_SPEC_FRC_SDCLK_ON
> [ 2.787536] sdhci-esdhc-imx 2194000.usdhc: change pinctrl state for uhs 0
> [ 2.787548] sdhci-esdhc-imx 2194000.usdhc: desired SD clock: 400000, actual: 386718
> [ 2.787554] mmc1: setting ESDHC_VENDOR_SPEC_FRC_SDCLK_ON
> [ 2.789560] mmc1: card failed to indicate switch to low voltage mode
>
> This appears to correspond with the sequence:
>
> CMD11 -> clock off -> set vselect -> clock on -> clock off ->
> set pinctrl -> clock on -> test D[3:0]
>
> which appears not to be the expected sequence - the expected sequence
> should be:
>
> CMD11 -> clock off -> set vselect -> clock on -> test D[3:0]
>
> maybe with the setting of the IOMUX settings somewhere in there -
> probably at the point where the clock is off - the additional clock
> off/clock on step looks to me incorrect.
>
> In any case, I've also augmented the other failure paths in
> mmc_set_signal_voltage(), and it's always this one (the last step)
> which fails:
>
> if (host->ops->card_busy && host->ops->card_busy(host)) {
> pr_debug("%s: card failed to indicate switch to low voltage mode\n",
> mmc_hostname(host));
> err = -EAGAIN;
> }
>
> Any ideas?
I'm not sure if it's the cause or you have it set up or not, but I
remember that we need to have 3 pinctrl states for 50MHz, 100MHz and
200MHz to get UHS card to work. You can look at
arch/arm/boot/dts/imx6qdl-sabreauto.dtsi for example.
Shawn
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