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authorSimon South <simon@simonsouth.net>2021-01-19 19:12:08 +0300
committerThierry Reding <thierry.reding@gmail.com>2021-01-20 20:13:15 +0300
commitd21ba5d6217bd5a6a696678385906ed1994b380b (patch)
tree44b17edbeb7329cc6ac4602b57edc0f698317515 /drivers/pwm/pwm-rockchip.c
parentc9f809d0db69572f360c3b59d611bb6f06498ac9 (diff)
downloadlinux-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.c9
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);