[PATCH] pwm: tiehrpwm: Clear period on disable to allow reconfiguration

[A. Sverdlin]

From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>

Both channels share one period register, so ehrpwm_pwm_config() rejects a
period differing from the sibling's period_cycles[]. That value was cleared
only in .free(), not in .disable(), so a stopped channel kept blocking the
sibling from switching to a new frequency. Clear it in .disable() too.

Testcase:

  cd /sys/class/pwm/pwmchip0; echo 0 > export; echo 1 > export
  for p in pwm0 pwm1; do
    echo 1000000 > $p/period; echo 500000 > $p/duty_cycle
    echo 1 > $p/enable; echo 0 > $p/enable; echo 2000000 > $p/period
  done
  echo 1 > pwm0/enable	# before: -EINVAL, after: succeeds

Fixes: 01b2d4536f02 ("pwm: pwm-tiehrpwm: Fix conflicting channel period setting")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
---
 drivers/pwm/pwm-tiehrpwm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pwm/pwm-tiehrpwm.c b/drivers/pwm/pwm-tiehrpwm.c
index 3a53489f0b982..e3407d0a1f7fe 100644
--- a/drivers/pwm/pwm-tiehrpwm.c
+++ b/drivers/pwm/pwm-tiehrpwm.c
@@ -358,6 +358,9 @@ static void ehrpwm_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 
 	/* Disable clock on PWM disable */
 	pm_runtime_put_sync(pwmchip_parent(chip));
+
+	/* A disabled channel must not constrain the sibling's period */
+	pc->period_cycles[pwm->hwpwm] = 0;
 }
 
 static void ehrpwm_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
-- 
2.55.0