[PATCH 6.6.y] pwm: tiehrpwm: Clear period on disable to allow reconfiguration

["Uwe Kleine-König" <ukleinek@kernel.org>]

From: Alexander Sverdlin <alexander.sverdlin@siemens.com>

[ Upstream commit e74b9a7ee50071aad25d3989bf985292f90b0c6e ]

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@vger.kernel.org
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Link: https://patch.msgid.link/20260929120806.2790355-1-alexander.sverdlin@siemens.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
---
 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 d693b2d65ccc..9af6cb08a01c 100644
--- a/drivers/pwm/pwm-tiehrpwm.c
+++ b/drivers/pwm/pwm-tiehrpwm.c
@@ -386,6 +386,9 @@ static void ehrpwm_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 
 	/* Disable clock on PWM disable */
 	pm_runtime_put_sync(chip->dev);
+
+	/* 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)
-- 
2.56.0.rc1