[PATCH 05/14] pwm: rockchip: Avoid glitches on already running PWMs
From: briannorris@chromium.org (Brian Norris)
Date: 2016-06-03 20:29:09
Also in:
linux-devicetree, linux-pwm, linux-rockchip, lkml
Hi, Just noticed a few things: On Fri, Jun 03, 2016 at 10:23:03AM +0200, Boris Brezillon wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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 dfacf7d..798a787 100644 --- a/drivers/pwm/pwm-rockchip.c +++ b/drivers/pwm/pwm-rockchip.c@@ -299,6 +299,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev) { const struct of_device_id *id; struct rockchip_pwm_chip *pc; + struct pwm_state state; struct resource *r; int ret;@@ -319,7 +320,7 @@ 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;@@ -342,12 +343,33 @@ 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, &state); + if (!state.enabled)
Why not just if (!pwm_is_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 state;
+
+ /*
+ * 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, &state);
+ if (state.enabled)Same here. With that: Reviewed-by: Brian Norris <briannorris@chromium.org> And it tests out fine: Tested-by: Brian Norris <briannorris@chromium.org>
+ clk_disable(pc->clk); clk_unprepare(pc->clk); -- 2.7.4