This is a note to let you know that I've just added the patch titled
pwm: rockchip: Eliminate potential race condition when probing
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
pwm-rockchip-eliminate-potential-race-condition-when.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 18898df13e0c27d3505828c89754f07f0e1fc469
Author: Simon South <simon@xxxxxxxxxxxxxx>
Date: Tue Jan 19 11:12:08 2021 -0500
pwm: rockchip: Eliminate potential race condition when probing
[ 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@xxxxxxxxx>
Signed-off-by: Simon South <simon@xxxxxxxxxxxxxx>
Signed-off-by: Thierry Reding <thierry.reding@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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);
