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[v4,1/5] pwm: rockchip: Enable APB clock during register access while probing

Message ID b16d8d5794235c469934c65a810ee00121be2acf.1610976129.git.simon@simonsouth.net
State Accepted
Headers show
Series pwm: rockchip: Eliminate potential race condition when probing | expand

Commit Message

Simon South Jan. 19, 2021, 4:12 p.m. UTC
Commit 457f74abbed0 ("pwm: rockchip: Keep enabled PWMs running while
probing") modified rockchip_pwm_probe() to access a PWM device's registers
directly to check whether or not the device is enabled, but did not also
change the function so it first enables the device's APB clock to be
certain the device can respond. This risks hanging the kernel on systems
with PWM devices that use more than a single clock.

Avoid this by enabling the device's APB clock before accessing its
registers (and disabling the clock when register access is complete).

Fixes: 457f74abbed0 ("pwm: rockchip: Keep enabled PWMs running while probing")
Reported-by: Thierry Reding <thierry.reding@gmail.com>
Suggested-by: Trent Piepho <tpiepho@gmail.com>
Signed-off-by: Simon South <simon@simonsouth.net>
 drivers/pwm/pwm-rockchip.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
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diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 389a5e140412..e6929bc73968 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -330,9 +330,9 @@  static int rockchip_pwm_probe(struct platform_device *pdev)
 		return ret;
-	ret = clk_prepare(pc->pclk);
+	ret = clk_prepare_enable(pc->pclk);
 	if (ret) {
-		dev_err(&pdev->dev, "Can't prepare APB clk: %d\n", ret);
+		dev_err(&pdev->dev, "Can't prepare enable APB clk: %d\n", ret);
 		goto err_clk;
@@ -362,10 +362,12 @@  static int rockchip_pwm_probe(struct platform_device *pdev)
 	if ((ctrl & enable_conf) != enable_conf)
+	clk_disable(pc->pclk);
 	return 0;
-	clk_unprepare(pc->pclk);
+	clk_disable_unprepare(pc->pclk);