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pwm: atmel-tcb: Fix race condition and convert to guards

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[ Upstream commit 37f7707077 ]

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: 9421bade07 ("pwm: atmel: add Timer Counter Block PWM driver")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20240709101806.52394-3-u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Uwe Kleine-König 2024-07-09 12:18:05 +02:00 committed by Greg Kroah-Hartman
parent 390645c5c1
commit 0804bd05f3
1 changed files with 5 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/pwm/pwm-atmel-tcb.c
View File

@ -82,7 +82,8 @@ 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
@ -108,7 +109,6 @@ 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;
}
@ -138,7 +138,6 @@ 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 */
@ -173,8 +172,6 @@ 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,
@ -195,7 +192,6 @@ 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 */
@ -257,7 +253,6 @@ 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;
}
@ -342,9 +337,12 @@ 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;