pwm: rcar: Fix a condition to prevent mismatch value setting to duty

commit 6225f9c64b40bc8a22503e9cda70f55d7a9dd3c6 upstream.

This patch fixes an issue that is possible to set mismatch value to duty
for R-Car PWM if we input the following commands:

 # cd /sys/class/pwm/<pwmchip>/
 # echo 0 > export
 # cd pwm0
 # echo 30 > period
 # echo 30 > duty_cycle
 # echo 0 > duty_cycle
 # cat duty_cycle
 0
 # echo 1 > enable
 --> Then, the actual duty_cycle is 30, not 0.

So, this patch adds a condition into rcar_pwm_config() to fix this
issue.

Signed-off-by: Ryo Kodama <ryo.kodama.vz@renesas.com>
[shimoda: revise the commit log and add Fixes and Cc tags]
Fixes: ed6c1476bf7f ("pwm: Add support for R-Car PWM Timer")
Cc: Cc: <stable@vger.kernel.org> # v4.4+
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
index 1c85ecc9e7ac076e7ad6e13333a1a6f4b15b07b6..0fcf94ffad321d8bb10911c6cdb65eebd8c8161b 100644 (file)
--- a/drivers/pwm/pwm-rcar.c
+++ b/drivers/pwm/pwm-rcar.c
@@ -156,8 +156,12 @@ static int rcar_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
        if (div < 0)
                return div;
 
-       /* Let the core driver set pwm->period if disabled and duty_ns == 0 */
-       if (!pwm_is_enabled(pwm) && !duty_ns)
+       /*
+        * Let the core driver set pwm->period if disabled and duty_ns == 0.
+        * But, this driver should prevent to set the new duty_ns if current
+        * duty_cycle is not set
+        */
+       if (!pwm_is_enabled(pwm) && !duty_ns && !pwm->state.duty_cycle)
                return 0;
 
        rcar_pwm_update(rp, RCAR_PWMCR_SYNC, RCAR_PWMCR_SYNC, RCAR_PWMCR);