pwm: rockchip: Avoid glitches on already running PWMs

The current logic will disable the PWM clk even if the PWM was left
enabled by the bootloader (because it's controlling a critical device
like a regulator for example).
Keep the PWM clk enabled if the PWM is enabled to avoid any glitches.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index c72b4192c7bf..dd8ca8663c24 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -319,7 +319,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
         if (IS_ERR(pc->clk))
                 return PTR_ERR(pc->clk);
 
-        ret = clk_prepare(pc->clk);
+        ret = clk_prepare_enable(pc->clk);
         if (ret)
                 return ret;
 
@@ -342,6 +342,10 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
                 dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
         }
 
+        /* Keep the PWM clk enabled if the PWM appears to be up and running. */
+        if (!pwm_is_enabled(pc->chip.pwms))
+                clk_disable(pc->clk);
+
         return ret;
 }
 
@@ -349,6 +353,20 @@ static int rockchip_pwm_remove(struct platform_device *pdev)
 {
         struct rockchip_pwm_chip *pc = platform_get_drvdata(pdev);
 
+        /*
+         * Disable the PWM clk before unpreparing it if the PWM device is still
+         * running. This should only happen when the last PWM user left it
+         * enabled, or when nobody requested a PWM that was previously enabled
+         * by the bootloader.
+         *
+         * FIXME: Maybe the core should disable all PWM devices in
+         * pwmchip_remove(). In this case we'd only have to call
+         * clk_unprepare() after pwmchip_remove().
+         *
+         */
+        if (pwm_is_enabled(pc->chip.pwms))
+                clk_disable(pc->clk);
+
         clk_unprepare(pc->clk);
 
         return pwmchip_remove(&pc->chip);