On 22 May 2018 at 00:35, Evan Green <evgreen@xxxxxxxxxxxx> wrote: > This change uses the appropriate _cansleep or non-sleeping API for > reading GPIO card detect state. This allows users with GPIOs that > never sleep to avoid a warning when certain quirks are present. > > The sdhci controller has an SDHCI_QUIRK_NO_CARD_NO_RESET, which > indicates that a controller will not reset properly if no card is > inserted. With this quirk enabled, mmc_get_cd_gpio is called in > several places with a spinlock held and interrupts disabled. > gpiod_get_raw_value_cansleep is not happy with this situation, > and throws out a warning. > > For boards that a) use controllers that have this quirk, and b) wire > card detect up to a GPIO that doesn't sleep, this is a spurious warning. > This change silences that warning, at the cost of pushing this problem > down to users that have sleeping GPIOs and controllers with this quirk. > > Signed-off-by: Evan Green <evgreen@xxxxxxxxxxxx> > --- > This is my initial solution to the warning I was trying to face down > in my previous RFC [1]. Upsides of this solution is it manages to > avoid the warning in places where the warning doesn't apply, and is > low-risk. Other approaches I considered: > > 1. Changing sdhci_get_cd to reach through mmc and get the GPIO value > directly (without sleeping) rather than calling mmc_gpio_get_cd, > which uses the cansleep functions. I didn't love this because a) it > seemed ugly to be reaching into mmc_host like that and b) I'd have to > duplicate the logic in mmc_gpio_get_cd, which seemed brittle. > > 2. Using mmc_gpio_set_cd_isr to record when the card detect pin > changes, and then in sdhci_do_reset we wouldn't actually need to > get CD state, just look at the cached value. This seemed risky to me > since it would affect all sdhci controllers, and I don't know that > everybody using gpio-cd can do interrupts on their pins. > > 3. Adding mmc_gpio_get_cd_nosleep(). That one's still doable if > preferred, but I'd have to give some thought to when sdhci wires > up to which one. First, I thought I preferred this option, as it becomes clear of what goes on. However I then realize, that it may not be worth it, because in the end I guess the caller (sdhci), will not be able to deal with error codes. For example, what would it do if it receives a -ENOTSUPP from mmc_gpio_get_cd_nosleep()? > > I'm up for other suggestions. This one most just seemed like the > best first stab of minimally addressing the warning without rocking > the boat otherwise. > > [1] https://patchwork.kernel.org/patch/10374633/ > --- > drivers/mmc/core/slot-gpio.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > diff --git a/drivers/mmc/core/slot-gpio.c b/drivers/mmc/core/slot-gpio.c > index 31f7dbb15668..0f497b69f4b8 100644 > --- a/drivers/mmc/core/slot-gpio.c > +++ b/drivers/mmc/core/slot-gpio.c > @@ -75,16 +75,22 @@ EXPORT_SYMBOL(mmc_gpio_get_ro); > > int mmc_gpio_get_cd(struct mmc_host *host) > { > + int can_sleep; > struct mmc_gpio *ctx = host->slot.handler_priv; > > if (!ctx || !ctx->cd_gpio) > return -ENOSYS; > > - if (ctx->override_cd_active_level) > - return !gpiod_get_raw_value_cansleep(ctx->cd_gpio) ^ > - !!(host->caps2 & MMC_CAP2_CD_ACTIVE_HIGH); > + can_sleep = gpiod_cansleep(ctx->cd_gpio); > + if (ctx->override_cd_active_level) { > + int value = can_sleep ? > + gpiod_get_raw_value_cansleep(ctx->cd_gpio) : > + gpiod_get_raw_value(ctx->cd_gpio); > + return !value ^ !!(host->caps2 & MMC_CAP2_CD_ACTIVE_HIGH); > + } > > - return gpiod_get_value_cansleep(ctx->cd_gpio); > + return can_sleep ? gpiod_get_value_cansleep(ctx->cd_gpio) : > + gpiod_get_value(ctx->cd_gpio); > } > EXPORT_SYMBOL(mmc_gpio_get_cd); > > -- > 2.13.5 > Kind regards Uffe -- 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
