Seungwon, On Wed, Jul 10, 2013 at 7:54 AM, Seungwon Jeon <tgih.jun@xxxxxxxxxxx> wrote: > On Wed, July 10, 2013, Doug Anderson wrote: >> If the WAKEUP_INT is asserted at wakeup and not cleared, we'll end up >> looping around forever. This has been seen to happen on exynos5420 >> silicon despite the fact that we haven't enabled any wakeup events. >> >> Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx> >> --- >> Changes in v2: >> - Use suspend_noirq as per James Hogan. >> >> drivers/mmc/host/dw_mmc-exynos.c | 23 +++++++++++++++++++++++ >> 1 file changed, 23 insertions(+) >> >> diff --git a/drivers/mmc/host/dw_mmc-exynos.c b/drivers/mmc/host/dw_mmc-exynos.c >> index f013e7e..36b9620 100644 >> --- a/drivers/mmc/host/dw_mmc-exynos.c >> +++ b/drivers/mmc/host/dw_mmc-exynos.c >> @@ -30,6 +30,7 @@ >> #define SDMMC_CLKSEL_TIMING(x, y, z) (SDMMC_CLKSEL_CCLK_SAMPLE(x) | \ >> SDMMC_CLKSEL_CCLK_DRIVE(y) | \ >> SDMMC_CLKSEL_CCLK_DIVIDER(z)) >> +#define SDMMC_CLKSEL_WAKEUP_INT BIT(11) >> >> #define SDMMC_CMD_USE_HOLD_REG BIT(29) >> >> @@ -102,6 +103,27 @@ static int dw_mci_exynos_setup_clock(struct dw_mci *host) >> return 0; >> } >> >> +/** >> + * dw_mci_exynos_resume_noirq - Exynos-specific resume code >> + * >> + * We have seen cases (at least on the exynos5420) where turning off the INT >> + * power rail during suspend will leave the WAKEUP_INT bit in the CLKSEL >> + * register asserted. This bit is 1 to indicate that it fired and we can >> + * clear it by writing a 1 back. Clear it to prevent interrupts from going off >> + * constantly. >> + */ > As I know this bit is auto-cleared. > Did you find the cause of this problem? > How about your GPIO setting in sleep? > Currently, we don't know why the problem is happened. > At least, we should make it clear. Yes, the documentation that I have says that this bit is "auto cleared" as well but doesn't indicate under what conditions it is auto cleared. From testing how this bit reacts I have found that writing a 1 to it clears the bit--in other words it behaves like bits in RINTSTS. That's a terrible design for a bit in a register with shared config but appears to be how it works. Note: in a sense it will be "auto cleared" because doing a read-modify-write of any other bits in this register will clear the interrupt. I have asked for official confirmation. We have found that on exynos5420 bits 8-10 of CLKSEL are marked as RESERVED. Those bits are documented to enable the WAKEUP_INT on exynos5250. My best guess is that these bits are not used on exynos5420 and the WAKEUP_INT line is left floating, which means it can fire randomly. I have also asked for official confirmation about this. I will likely merge this change locally in our kernel tree while waiting for a response. If you would like to wait before Acking that's very reasonable. Do you have any other problems with this change assuming my understanding above is correct? -Doug -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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