linux-kernel - [PATCH 5.15 154/171] iio: adc: stm32: fix a current leak by resetting pcsel before disabling vdda

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Date:   Mon, 13 Dec 2021 10:31:09 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Fabrice Gasnier <fabrice.gasnier@...s.st.com>,
        Olivier Moysan <olivier.moysan@...s.st.com>,
        Stable@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [PATCH 5.15 154/171] iio: adc: stm32: fix a current leak by resetting pcsel before disabling vdda

From: Fabrice Gasnier <fabrice.gasnier@...s.st.com>

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@...s.st.com>
Reviewed-by: Olivier Moysan <olivier.moysan@...s.st.com>
Link: https://lore.kernel.org/r/1634905169-23762-1-git-send-email-fabrice.gasnier@foss.st.com
Cc: <Stable@...r.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/iio/adc/stm32-adc.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -975,6 +975,7 @@ static void stm32h7_adc_unprepare(struct
 {
 	struct stm32_adc *adc = iio_priv(indio_dev);
 
+	stm32_adc_writel(adc, STM32H7_ADC_PCSEL, 0);
 	stm32h7_adc_disable(indio_dev);
 	stm32h7_adc_enter_pwr_down(adc);
 }