pwm: tiehrpwm: Update shadow register for disabling PWMs

[ Upstream commit b00ef53053191d3025c15e8041699f8c9d132daf ]

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: NChristoph Vogtländer <c.vogtlaender@sigma-surface-science.com>
[vigneshr@ti.com: Improve commit message]
Signed-off-by: NVignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>

drivers/pwm/pwm-tiehrpwm.c

@@ -382,6 +382,8 @@ 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