[PATCH 5.4] iio: adc: stm32: fix a current leak by resetting pcsel before disabling vdda

[PATCH 5.4] iio: adc: stm32: fix a current leak by resetting pcsel before disabling vdda

[Fabrice Gasnier]

commit f711f28e71e965c0d1141c830fa7131b41abbe75 upstream.

Some I/Os are connected to ADC input channels, when the corresponding bit
in PCSEL register are set on STM32H7 and STM32MP15. This is done in the
prepare routine of stm32-adc driver.
There are constraints here, as PCSEL shouldn't be set when VDDA supply
is disabled. Enabling/disabling of VDDA supply in done via stm32-adc-core
runtime PM routines (before/after ADC is enabled/disabled).

Currently, PCSEL remains set when disabling ADC. Later on, PM runtime
can disable the VDDA supply. This creates some conditions on I/Os that
can start to leak current.
So PCSEL needs to be cleared when disabling the ADC.

Fixes: 95e339b6e85d ("iio: adc: stm32: add support for STM32H7")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Reviewed-by: Olivier Moysan <olivier.moysan@foss.st.com>
Link: https://lore.kernel.org/r/1634905169-23762-1-git-send-email-fabrice.gasnier@foss.st.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Backport for 5.4-stable
---
 drivers/iio/adc/stm32-adc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 94fde39..d1bbd2b 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -933,6 +933,7 @@ static int stm32h7_adc_prepare(struct stm32_adc *adc)
 
 static void stm32h7_adc_unprepare(struct stm32_adc *adc)
 {
+	stm32_adc_writel(adc, STM32H7_ADC_PCSEL, 0);
 	stm32h7_adc_disable(adc);
 	stm32h7_adc_enter_pwr_down(adc);
 }
-- 
2.7.4

Re: [PATCH 5.4] iio: adc: stm32: fix a current leak by resetting pcsel before disabling vdda

[Greg KH]

On Fri, Dec 17, 2021 at 11:56:32AM +0100, Fabrice Gasnier wrote:
> commit f711f28e71e965c0d1141c830fa7131b41abbe75 upstream.
> 
> Some I/Os are connected to ADC input channels, when the corresponding bit
> in PCSEL register are set on STM32H7 and STM32MP15. This is done in the
> prepare routine of stm32-adc driver.
> There are constraints here, as PCSEL shouldn't be set when VDDA supply
> is disabled. Enabling/disabling of VDDA supply in done via stm32-adc-core
> runtime PM routines (before/after ADC is enabled/disabled).
> 
> Currently, PCSEL remains set when disabling ADC. Later on, PM runtime
> can disable the VDDA supply. This creates some conditions on I/Os that
> can start to leak current.
> So PCSEL needs to be cleared when disabling the ADC.
> 
> Fixes: 95e339b6e85d ("iio: adc: stm32: add support for STM32H7")
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
> Reviewed-by: Olivier Moysan <olivier.moysan@foss.st.com>
> Link: https://lore.kernel.org/r/1634905169-23762-1-git-send-email-fabrice.gasnier@foss.st.com
> Cc: <Stable@vger.kernel.org>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
> Backport for 5.4-stable

Now queued up, thanks.

greg k-h