pwm: tiehrpwm: Update shadow register for disabling PWMs

BugLink: https://bugs.launchpad.net/bugs/1836666

[ Upstream commit b00ef530 ]

It must be made sure that immediate mode is not already set, when
modifying shadow register value in ehrpwm_pwm_disable(). Otherwise
modifications to the action-qualifier continuous S/W force
register(AQSFRC) will be done in the active register.
This may happen when both channels are being disabled. In this case,
only the first channel state will be recorded as disabled in the shadow
register. Later, when enabling the first channel again, the second
channel would be enabled as well. Setting RLDCSF to zero, first, ensures
that the shadow register is updated as desired.

Fixes: 38dabd91 ("pwm: tiehrpwm: Fix disabling of output of PWMs")
Signed-off-by: Christoph Vogtländer <c.vogtlaender@sigma-surface-science.com>
[vigneshr@ti.com: Improve commit message]
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/pwm/pwm-tiehrpwm.c

@@ -385,6 +385,8 @@ static void ehrpwm_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 	}
 
 	/* Update shadow register first before modifying active register */
+	ehrpwm_modify(pc->mmio_base, AQSFRC, AQSFRC_RLDCSF_MASK,
+		      AQSFRC_RLDCSF_ZRO);
 	ehrpwm_modify(pc->mmio_base, AQCSFRC, aqcsfrc_mask, aqcsfrc_val);
 	/*
 	 * Changes to immediate action on Action Qualifier. This puts