[ Upstream commit 002ee28e8b322d4d4b7b83234b5d0f4ebd428eda ]
pwrseq_emmc.c implements a HW reset procedure for eMMC chip by driving a GPIO line.
It registers the .reset() cb on mmc_pwrseq_ops and it registers a system restart notification handler; both of them perform reset by unconditionally calling gpiod_set_value().
If the eMMC reset line is tied to a GPIO controller whose driver can sleep (i.e. I2C GPIO controller), then the kernel would spit warnings when trying to reset the eMMC chip by means of .reset() mmc_pwrseq_ops cb (that is exactly what I'm seeing during boot).
Furthermore, on system reset we would gets to the system restart notification handler with disabled interrupts - local_irq_disable() is called in machine_restart() at least on ARM/ARM64 - and we would be in trouble when the GPIO driver tries to sleep (which indeed doesn't happen here, likely because in my case the machine specific code doesn't call do_kernel_restart(), I guess..).
This patch fixes the .reset() cb to make use of gpiod_set_value_cansleep(), so that the eMMC gets reset on boot without complaints, while, since there isn't that much we can do, we avoid register the restart handler if the GPIO controller has a sleepy driver (and we spit a dev_notice() message to let people know)..
This had been tested on a downstream 4.9 kernel with backported commit 83f37ee7ba33 ("mmc: pwrseq: Add reset callback to the struct mmc_pwrseq_ops") and commit ae60fb031cf2 ("mmc: core: Don't do eMMC HW reset when resuming the eMMC card"), because I couldn't boot my board otherwise. Maybe worth to RFT.
Signed-off-by: Andrea Merello andrea.merello@gmail.com Signed-off-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/mmc/core/pwrseq_emmc.c | 38 ++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 18 deletions(-)
diff --git a/drivers/mmc/core/pwrseq_emmc.c b/drivers/mmc/core/pwrseq_emmc.c index efb8a7965dd4a..154f4204d58cb 100644 --- a/drivers/mmc/core/pwrseq_emmc.c +++ b/drivers/mmc/core/pwrseq_emmc.c @@ -30,19 +30,14 @@ struct mmc_pwrseq_emmc {
#define to_pwrseq_emmc(p) container_of(p, struct mmc_pwrseq_emmc, pwrseq)
-static void __mmc_pwrseq_emmc_reset(struct mmc_pwrseq_emmc *pwrseq) -{ - gpiod_set_value(pwrseq->reset_gpio, 1); - udelay(1); - gpiod_set_value(pwrseq->reset_gpio, 0); - udelay(200); -} - static void mmc_pwrseq_emmc_reset(struct mmc_host *host) { struct mmc_pwrseq_emmc *pwrseq = to_pwrseq_emmc(host->pwrseq);
- __mmc_pwrseq_emmc_reset(pwrseq); + gpiod_set_value_cansleep(pwrseq->reset_gpio, 1); + udelay(1); + gpiod_set_value_cansleep(pwrseq->reset_gpio, 0); + udelay(200); }
static int mmc_pwrseq_emmc_reset_nb(struct notifier_block *this, @@ -50,8 +45,11 @@ static int mmc_pwrseq_emmc_reset_nb(struct notifier_block *this, { struct mmc_pwrseq_emmc *pwrseq = container_of(this, struct mmc_pwrseq_emmc, reset_nb); + gpiod_set_value(pwrseq->reset_gpio, 1); + udelay(1); + gpiod_set_value(pwrseq->reset_gpio, 0); + udelay(200);
- __mmc_pwrseq_emmc_reset(pwrseq); return NOTIFY_DONE; }
@@ -72,14 +70,18 @@ static int mmc_pwrseq_emmc_probe(struct platform_device *pdev) if (IS_ERR(pwrseq->reset_gpio)) return PTR_ERR(pwrseq->reset_gpio);
- /* - * register reset handler to ensure emmc reset also from - * emergency_reboot(), priority 255 is the highest priority - * so it will be executed before any system reboot handler. - */ - pwrseq->reset_nb.notifier_call = mmc_pwrseq_emmc_reset_nb; - pwrseq->reset_nb.priority = 255; - register_restart_handler(&pwrseq->reset_nb); + if (!gpiod_cansleep(pwrseq->reset_gpio)) { + /* + * register reset handler to ensure emmc reset also from + * emergency_reboot(), priority 255 is the highest priority + * so it will be executed before any system reboot handler. + */ + pwrseq->reset_nb.notifier_call = mmc_pwrseq_emmc_reset_nb; + pwrseq->reset_nb.priority = 255; + register_restart_handler(&pwrseq->reset_nb); + } else { + dev_notice(dev, "EMMC reset pin tied to a sleepy GPIO driver; reset on emergency-reboot disabled\n"); + }
pwrseq->pwrseq.ops = &mmc_pwrseq_emmc_ops; pwrseq->pwrseq.dev = dev;