[PATCH] [RFC] regulator: stm32-pwr: Fix regulator disabling

[Marek Vasut]

The following shows up in the kernel log on systems using the STM32MP15xx USBPHYC:
"
regulator regulator.19: regulator disable timed out!
reg18: failed to disable: -ETIMEDOUT
"
This 'regulator.19' is 'pwr at 50001000' 'reg18' in stm32mp151.dts DT, or
"Power control (PWR)" register "PWR_CR3" bits "REG18" on STM32MP15xx
reference manual.

The reason for the timeout seems to be the poll which this patch changes.
When turning this regulator OFF, PWR_CR3 reads 0xf0000000 , then REG18_EN
bit is cleared, and then this poll waits until REG18_RDY bit is cleared as
well, but that never happens, the PWR_CR3 keeps reading 0xe0000000 .

I am not sure whether this should happen, I suspect the 1V8 supply is
always READY when the 1V8 input is present, and the regulator can only
ever be enabled/disabled using the REG18_EN bit, but the REG18_READY
bit is never cleared again.

This patch adjusts the poll to check whether REG18_EN has been cleared
on regulator disable, but retains the check for REG18_READY in regulator
enable as there it makes sense to verify the regulator is really READY.

Signed-off-by: Marek Vasut <marex at denx.de>
---
NOTE: Input from ST on behavior of this regulator would be very welcome,
      as well as on this patch.
---
Cc: Alexandre Torgue <alexandre.torgue at foss.st.com>
Cc: Liam Girdwood <lgirdwood at gmail.com>
Cc: Mark Brown <broonie at kernel.org>
Cc: Maxime Coquelin <mcoquelin.stm32 at gmail.com>
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-stm32 at st-md-mailman.stormreply.com
---
 drivers/regulator/stm32-pwr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/regulator/stm32-pwr.c b/drivers/regulator/stm32-pwr.c
index 0e101dff6ddad..4c60eddad60d0 100644
--- a/drivers/regulator/stm32-pwr.c
+++ b/drivers/regulator/stm32-pwr.c
@@ -93,7 +93,7 @@ static int stm32_pwr_reg_disable(struct regulator_dev *rdev)
 	writel_relaxed(val, priv->base + REG_PWR_CR3);
 
 	/* use an arbitrary timeout of 20ms */
-	ret = readx_poll_timeout(stm32_pwr_reg_is_ready, rdev, val, !val,
+	ret = readx_poll_timeout(stm32_pwr_reg_is_enabled, rdev, val, !val,
 				 100, 20 * 1000);
 	if (ret)
 		dev_err(&rdev->dev, "regulator disable timed out!\n");
-- 
2.39.2