linux-kernel - [PATCH] iio: adc: stm32: fix a leak by resetting pcsel before disabling vdda

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Message-ID: <1634905169-23762-1-git-send-email-fabrice.gasnier@foss.st.com>
Date:   Fri, 22 Oct 2021 14:19:29 +0200
From:   Fabrice Gasnier <fabrice.gasnier@...s.st.com>
To:     <jic23@...nel.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <alexandre.torgue@...s.st.com>,
        <fabrice.gasnier@...s.st.com>, <olivier.moysan@...s.st.com>,
        <linux-iio@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>
Subject: [PATCH] iio: adc: stm32: fix a leak by resetting pcsel before disabling vdda

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>
---
 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 5088de8..e3e7541 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -975,6 +975,7 @@ static void stm32h7_adc_unprepare(struct iio_dev *indio_dev)
 {
 	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);
 }
-- 
2.7.4