From: Simon South simon@simonsouth.net
[ Upstream commit d21ba5d6217bd5a6a696678385906ed1994b380b ]
Commit 48cf973cae33 ("pwm: rockchip: Avoid glitches on already running PWMs") introduced a potential race condition in rockchip_pwm_probe(): A consumer could enable an inactive PWM, or disable a running one, between rockchip_pwm_probe() registering the device via pwmchip_add() and checking whether it is enabled (to determine whether it was started by a bootloader). This could result in a device's PWM clock being either enabled once more than necessary, potentially causing it to continue running when no longer needed, or disabled once more than necessary, producing a warning from the kernel.
Eliminate these possibilities by modifying rockchip_pwm_probe() so it checks whether a device is enabled before registering it rather than after.
Fixes: 48cf973cae33 ("pwm: rockchip: Avoid glitches on already running PWMs") Reported-by: Trent Piepho tpiepho@gmail.com Signed-off-by: Simon South simon@simonsouth.net Signed-off-by: Thierry Reding thierry.reding@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/pwm/pwm-rockchip.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c index ede027fbf2bb4..3b8da7b0091b1 100644 --- a/drivers/pwm/pwm-rockchip.c +++ b/drivers/pwm/pwm-rockchip.c @@ -289,6 +289,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev) struct rockchip_pwm_chip *pc; struct resource *r; u32 enable_conf, ctrl; + bool enabled; int ret, count;
id = of_match_device(rockchip_pwm_dt_ids, &pdev->dev); @@ -351,6 +352,10 @@ static int rockchip_pwm_probe(struct platform_device *pdev) pc->chip.of_pwm_n_cells = 3; }
+ enable_conf = pc->data->enable_conf; + ctrl = readl_relaxed(pc->base + pc->data->regs.ctrl); + enabled = (ctrl & enable_conf) == enable_conf; + ret = pwmchip_add(&pc->chip); if (ret < 0) { dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret); @@ -358,9 +363,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev) }
/* Keep the PWM clk enabled if the PWM appears to be up and running. */ - enable_conf = pc->data->enable_conf; - ctrl = readl_relaxed(pc->base + pc->data->regs.ctrl); - if ((ctrl & enable_conf) != enable_conf) + if (!enabled) clk_disable(pc->clk);
clk_disable(pc->pclk);