This is a note to let you know that I've just added the patch titled
pwm: atmel-tcb: Fix race condition and convert to guards
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
pwm-atmel-tcb-fix-race-condition-and-convert-to-guar.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4d5509fc95c25a7a8e824bb5139fe2690ba50a2a
Author: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxx>
Date: Tue Jul 9 12:18:05 2024 +0200
pwm: atmel-tcb: Fix race condition and convert to guards
[ Upstream commit 37f7707077f5ea2515bf4b1dc7fad43f8e12993e ]
The hardware only supports a single period length for both PWM outputs. So
atmel_tcb_pwm_config() checks the configuration of the other output if it's
compatible with the currently requested setting. The register values are
then actually updated in atmel_tcb_pwm_enable(). To make this race free
the lock must be held during the whole process, so grab the lock in
.apply() instead of individually in atmel_tcb_pwm_disable() and
atmel_tcb_pwm_enable() which then also covers atmel_tcb_pwm_config().
To simplify handling, use the guard helper to let the compiler care for
unlocking. Otherwise unlocking would be more difficult as there is more
than one exit path in atmel_tcb_pwm_apply().
Fixes: 9421bade0765 ("pwm: atmel: add Timer Counter Block PWM driver")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxx>
Acked-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240709101806.52394-3-u.kleine-koenig@xxxxxxxxxxxx
Signed-off-by: Uwe Kleine-König <ukleinek@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/pwm/pwm-atmel-tcb.c b/drivers/pwm/pwm-atmel-tcb.c
index 30c966238e41c..e74b45f00a9ac 100644
--- a/drivers/pwm/pwm-atmel-tcb.c
+++ b/drivers/pwm/pwm-atmel-tcb.c
@@ -83,7 +83,8 @@ static int atmel_tcb_pwm_request(struct pwm_chip *chip,
tcbpwm->period = 0;
tcbpwm->div = 0;
- spin_lock(&tcbpwmc->lock);
+ guard(spinlock)(&tcbpwmc->lock);
+
regmap_read(tcbpwmc->regmap, ATMEL_TC_REG(tcbpwmc->channel, CMR), &cmr);
/*
* Get init config from Timer Counter registers if
@@ -109,7 +110,6 @@ static int atmel_tcb_pwm_request(struct pwm_chip *chip,
cmr |= ATMEL_TC_WAVE | ATMEL_TC_WAVESEL_UP_AUTO | ATMEL_TC_EEVT_XC0;
regmap_write(tcbpwmc->regmap, ATMEL_TC_REG(tcbpwmc->channel, CMR), cmr);
- spin_unlock(&tcbpwmc->lock);
return 0;
}
@@ -139,7 +139,6 @@ static void atmel_tcb_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm,
if (tcbpwm->duty == 0)
polarity = !polarity;
- spin_lock(&tcbpwmc->lock);
regmap_read(tcbpwmc->regmap, ATMEL_TC_REG(tcbpwmc->channel, CMR), &cmr);
/* flush old setting and set the new one */
@@ -174,8 +173,6 @@ static void atmel_tcb_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm,
ATMEL_TC_SWTRG);
tcbpwmc->bkup.enabled = 0;
}
-
- spin_unlock(&tcbpwmc->lock);
}
static int atmel_tcb_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm,
@@ -196,7 +193,6 @@ static int atmel_tcb_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm,
if (tcbpwm->duty == 0)
polarity = !polarity;
- spin_lock(&tcbpwmc->lock);
regmap_read(tcbpwmc->regmap, ATMEL_TC_REG(tcbpwmc->channel, CMR), &cmr);
/* flush old setting and set the new one */
@@ -258,7 +254,6 @@ static int atmel_tcb_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm,
regmap_write(tcbpwmc->regmap, ATMEL_TC_REG(tcbpwmc->channel, CCR),
ATMEL_TC_SWTRG | ATMEL_TC_CLKEN);
tcbpwmc->bkup.enabled = 1;
- spin_unlock(&tcbpwmc->lock);
return 0;
}
@@ -343,9 +338,12 @@ static int atmel_tcb_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
static int atmel_tcb_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
+ struct atmel_tcb_pwm_chip *tcbpwmc = to_tcb_chip(chip);
int duty_cycle, period;
int ret;
+ guard(spinlock)(&tcbpwmc->lock);
+
if (!state->enabled) {
atmel_tcb_pwm_disable(chip, pwm, state->polarity);
return 0;
