linux-kernel - [PATCH] pwm: stm32-lp: fix the check on arr and cmp registers update

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Message-ID: <20221123133652.465724-1-fabrice.gasnier@foss.st.com>
Date:   Wed, 23 Nov 2022 14:36:52 +0100
From:   Fabrice Gasnier <fabrice.gasnier@...s.st.com>
To:     <thierry.reding@...il.com>, <u.kleine-koenig@...gutronix.de>
CC:     <alexandre.torgue@...s.st.com>, <fabrice.gasnier@...s.st.com>,
        <linux-pwm@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <olivier.moysan@...s.st.com>
Subject: [PATCH] pwm: stm32-lp: fix the check on arr and cmp registers update

The ARR (auto reload register) and CMP (compare) registers are
successively written. The status bits to check the update of these
registers are polled together with regmap_read_poll_timeout().
The condition to end the loop may become true, even if one of the
register isn't correctly updated.
So ensure both status bits are set before clearing them.

Fixes: e70a540b4e02 ("pwm: Add STM32 LPTimer PWM driver")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
---
 drivers/pwm/pwm-stm32-lp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-stm32-lp.c b/drivers/pwm/pwm-stm32-lp.c
index 3115abb3f52a..61a1c87cd501 100644
--- a/drivers/pwm/pwm-stm32-lp.c
+++ b/drivers/pwm/pwm-stm32-lp.c
@@ -127,7 +127,7 @@ static int stm32_pwm_lp_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	/* ensure CMP & ARR registers are properly written */
 	ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
-				       (val & STM32_LPTIM_CMPOK_ARROK),
+				       (val & STM32_LPTIM_CMPOK_ARROK) == STM32_LPTIM_CMPOK_ARROK,
 				       100, 1000);
 	if (ret) {
 		dev_err(priv->chip.dev, "ARR/CMP registers write issue\n");
-- 
2.25.1