[PATCH v5 22/46] pwm: rockchip: avoid glitches on already running PWMs

Boris Brezillon
2016-03-30T20:05:23Z

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>
---
drivers/pwm/pwm-rockchip.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 6a1087c..5c7e79c 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -302,6 +302,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
{
const struct of_device_id *id;
struct rockchip_pwm_chip *pc;
+ struct pwm_state pstate;
struct resource *r;
int ret;

@@ -322,7 +323,7 @@ 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;

@@ -345,12 +346,33 @@ 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. */
+ pwm_get_state(pc->chip.pwms, &pstate);
+ if (!pstate.enabled)
+ clk_disable(pc->clk);
+
return ret;
}

static int rockchip_pwm_remove(struct platform_device *pdev)
{
struct rockchip_pwm_chip *pc = platform_get_drvdata(pdev);
+ struct pwm_state pstate;
+
+ /*
+ * 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().
+ *
+ */
+ pwm_get_state(pc->chip.pwms, &pstate);
+ if (pstate.enabled)
+ clk_disable(pc->clk);

clk_unprepare(pc->clk);

--
2.5.0