| Message ID | 49ceda3def13f6186073745e99d7315c974bfa81.1608407584.git.simon@simonsouth.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | pwm: rockchip: Eliminate potential race condition when probing | expand |
Hello, On Sat, Dec 19, 2020 at 03:44:08PM -0500, Simon South wrote: > 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 running, but did not also > change the function to first enable 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> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Best regards Uwe
diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c index 77c23a2c6d71..d2058138ce1e 100644 --- a/drivers/pwm/pwm-rockchip.c +++ b/drivers/pwm/pwm-rockchip.c @@ -332,9 +332,9 @@ 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 enable APB clk: %d\n", ret); goto err_clk; } @@ -364,10 +364,12 @@ static int rockchip_pwm_probe(struct platform_device *pdev) if ((ctrl & enable_conf) != enable_conf) clk_disable(pc->clk); + clk_disable(pc->pclk); + return 0; err_pclk: - clk_unprepare(pc->pclk); + clk_disable_unprepare(pc->pclk); err_clk: clk_disable_unprepare(pc->clk);
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 running, but did not also change the function to first enable 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(-)