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Subject[PATCH 4.19 163/276] mmc: core: make pwrseq_emmc (partially) support sleepy GPIO controllers
Date
[ 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;
--
2.20.1


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