diff options
| author | Simon South <simon@simonsouth.net> | 2021-01-19 19:12:08 +0300 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@gmail.com> | 2021-01-20 20:13:15 +0300 |
| commit | d21ba5d6217bd5a6a696678385906ed1994b380b (patch) | |
| tree | 44b17edbeb7329cc6ac4602b57edc0f698317515 /drivers/pwm/pwm-rockchip.c | |
| parent | c9f809d0db69572f360c3b59d611bb6f06498ac9 (diff) | |
| download | linux-d21ba5d6217bd5a6a696678385906ed1994b380b.tar.xz | |
pwm: rockchip: Eliminate potential race condition when probing
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>
Diffstat (limited to 'drivers/pwm/pwm-rockchip.c')
| -rw-r--r-- | drivers/pwm/pwm-rockchip.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c index b5bab427b5de..228147e9bc6e 100644 --- a/drivers/pwm/pwm-rockchip.c +++ b/drivers/pwm/pwm-rockchip.c @@ -288,6 +288,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev) const struct of_device_id *id; struct rockchip_pwm_chip *pc; u32 enable_conf, ctrl; + bool enabled; int ret, count; id = of_match_device(rockchip_pwm_dt_ids, &pdev->dev); @@ -349,6 +350,10 @@ 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); @@ -356,9 +361,7 @@ 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); |