linux-kernel - [PATCH 3.16 034/328] pwm: tiehrpwm: Fix disabling of output of PWMs

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Message-ID: <lsq.1544392233.209980543@decadent.org.uk>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Thierry Reding" <thierry.reding@...il.com>,
        "Vignesh R" <vigneshr@...com>
Subject: [PATCH 3.16 034/328] pwm: tiehrpwm: Fix disabling of output of PWMs

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Vignesh R <vigneshr@...com>

commit 38dabd91ff0bde33352ca3cc65ef515599b77a05 upstream.

pwm-tiehrpwm driver disables PWM output by putting it in low output
state via active AQCSFRC register in ehrpwm_pwm_disable(). But, the
AQCSFRC shadow register is not updated. Therefore, when shadow AQCSFRC
register is re-enabled in ehrpwm_pwm_enable() (say to enable second PWM
output), previous settings are lost as shadow register value is loaded
into active register. This results in things like PWMA getting enabled
automatically, when PWMB is enabled and vice versa. Fix this by
updating AQCSFRC shadow register as well during ehrpwm_pwm_disable().

Fixes: 19891b20e7c2 ("pwm: pwm-tiehrpwm: PWM driver support for EHRPWM")
Signed-off-by: Vignesh R <vigneshr@...com>
Signed-off-by: Thierry Reding <thierry.reding@...il.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/pwm/pwm-tiehrpwm.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/pwm/pwm-tiehrpwm.c
+++ b/drivers/pwm/pwm-tiehrpwm.c
@@ -378,6 +378,8 @@ static void ehrpwm_pwm_disable(struct pw
 		aqcsfrc_mask = AQCSFRC_CSFA_MASK;
 	}

+	/* Update shadow register first before modifying active register */
+	ehrpwm_modify(pc->mmio_base, AQCSFRC, aqcsfrc_mask, aqcsfrc_val);
 	/*
 	 * Changes to immediate action on Action Qualifier. This puts
 	 * Action Qualifier control on PWM output from next TBCLK