[PATCH v4 0/5] pwm: rockchip: Eliminate potential race condition when probing

[PATCH v4 0/5] pwm: rockchip: Eliminate potential race condition when probing

[Simon South]

This patch series eliminates the race condition Trent Piepho
identified[0] in the Rockchip PWM driver's rockchip_pwm_probe()
function, by moving code that checks whether a device is enabled ahead
of the code that registers it via pwmchip_add().

It includes several other small fixes and improvements to the driver
as well: It also

- Fixes a potential kernel hang introduced by my earlier commit
  457f74abbed0 ("pwm: rockchip: Keep enabled PWMs running while
  probing") by ensuring a device's APB clock is enabled before its
  registers are accessed;

- Removes a superfluous call to clk_unprepare() that could produce
  warnings from the kernel;

- Clarifies error messages from the driver by replacing "bus clk" with
  "PWM clk"; and

- Ensures the driver enables a clock before querying its rate with
  clk_get_rate(), as stated as a requirement in that function's
  documentation.

This version of the series incorporates Uwe Kleine-König's feedback on
v3 and includes these changes:

- Patch 1's commit message has been edited slightly to improve
  readability, and the error message updated by the patch now reads
  "prepare enable" rather than just "enable" for consistency with the
  error message above it in the code.

- Patch 3's commit message now mentions consistency with the device
  tree.

- Patch 4 has been simplified and now just moves the device-enabled
  check ahead of the call to pwmchip_add(). It no longers changes any
  error-handling behaviour, and an extraneous pair of parentheses has
  been removed.

Patches 2 and 5 are unchanged from v3, while the remaining 2 patches
present in v3 (which removed goto targets from and reordered some
operations in rockchip_pwm_probe()) have been dropped.

I've tested these changes on my Pinebook Pro (RK3399 with a PWM-driven
backlight enabled by U-Boot) and ROCK64 (RK3328) and they appear to
work fine.

[0] https://www.spinics.net/lists/linux-pwm/msg14611.html

--
Simon South
simon@simonsouth.net


Simon South (5):
  pwm: rockchip: Enable APB clock during register access while probing
  pwm: rockchip: rockchip_pwm_probe(): Remove superfluous
    clk_unprepare()
  pwm: rockchip: Replace "bus clk" with "PWM clk"
  pwm: rockchip: Eliminate potential race condition when probing
  pwm: rockchip: Enable clock before calling clk_get_rate()

 drivers/pwm/pwm-rockchip.c | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

-- 
2.30.0

[PATCH v4 0/5] pwm: rockchip: Eliminate potential race condition when probing

[Simon South]

This patch series eliminates the race condition Trent Piepho
identified[0] in the Rockchip PWM driver's rockchip_pwm_probe()
function, by moving code that checks whether a device is enabled ahead
of the code that registers it via pwmchip_add().

It includes several other small fixes and improvements to the driver
as well: It also

- Fixes a potential kernel hang introduced by my earlier commit
  457f74abbed0 ("pwm: rockchip: Keep enabled PWMs running while
  probing") by ensuring a device's APB clock is enabled before its
  registers are accessed;

- Removes a superfluous call to clk_unprepare() that could produce
  warnings from the kernel;

- Clarifies error messages from the driver by replacing "bus clk" with
  "PWM clk"; and

- Ensures the driver enables a clock before querying its rate with
  clk_get_rate(), as stated as a requirement in that function's
  documentation.

This version of the series incorporates Uwe Kleine-König's feedback on
v3 and includes these changes:

- Patch 1's commit message has been edited slightly to improve
  readability, and the error message updated by the patch now reads
  "prepare enable" rather than just "enable" for consistency with the
  error message above it in the code.

- Patch 3's commit message now mentions consistency with the device
  tree.

- Patch 4 has been simplified and now just moves the device-enabled
  check ahead of the call to pwmchip_add(). It no longers changes any
  error-handling behaviour, and an extraneous pair of parentheses has
  been removed.

Patches 2 and 5 are unchanged from v3, while the remaining 2 patches
present in v3 (which removed goto targets from and reordered some
operations in rockchip_pwm_probe()) have been dropped.

I've tested these changes on my Pinebook Pro (RK3399 with a PWM-driven
backlight enabled by U-Boot) and ROCK64 (RK3328) and they appear to
work fine.

[0] https://www.spinics.net/lists/linux-pwm/msg14611.html

--
Simon South
simon@simonsouth.net


Simon South (5):
  pwm: rockchip: Enable APB clock during register access while probing
  pwm: rockchip: rockchip_pwm_probe(): Remove superfluous
    clk_unprepare()
  pwm: rockchip: Replace "bus clk" with "PWM clk"
  pwm: rockchip: Eliminate potential race condition when probing
  pwm: rockchip: Enable clock before calling clk_get_rate()

 drivers/pwm/pwm-rockchip.c | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

-- 
2.30.0


_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip

[PATCH v4 0/5] pwm: rockchip: Eliminate potential race condition when probing

[Simon South]

This patch series eliminates the race condition Trent Piepho
identified[0] in the Rockchip PWM driver's rockchip_pwm_probe()
function, by moving code that checks whether a device is enabled ahead
of the code that registers it via pwmchip_add().

It includes several other small fixes and improvements to the driver
as well: It also

- Fixes a potential kernel hang introduced by my earlier commit
  457f74abbed0 ("pwm: rockchip: Keep enabled PWMs running while
  probing") by ensuring a device's APB clock is enabled before its
  registers are accessed;

- Removes a superfluous call to clk_unprepare() that could produce
  warnings from the kernel;

- Clarifies error messages from the driver by replacing "bus clk" with
  "PWM clk"; and

- Ensures the driver enables a clock before querying its rate with
  clk_get_rate(), as stated as a requirement in that function's
  documentation.

This version of the series incorporates Uwe Kleine-König's feedback on
v3 and includes these changes:

- Patch 1's commit message has been edited slightly to improve
  readability, and the error message updated by the patch now reads
  "prepare enable" rather than just "enable" for consistency with the
  error message above it in the code.

- Patch 3's commit message now mentions consistency with the device
  tree.

- Patch 4 has been simplified and now just moves the device-enabled
  check ahead of the call to pwmchip_add(). It no longers changes any
  error-handling behaviour, and an extraneous pair of parentheses has
  been removed.

Patches 2 and 5 are unchanged from v3, while the remaining 2 patches
present in v3 (which removed goto targets from and reordered some
operations in rockchip_pwm_probe()) have been dropped.

I've tested these changes on my Pinebook Pro (RK3399 with a PWM-driven
backlight enabled by U-Boot) and ROCK64 (RK3328) and they appear to
work fine.

[0] https://www.spinics.net/lists/linux-pwm/msg14611.html

--
Simon South
simon@simonsouth.net


Simon South (5):
  pwm: rockchip: Enable APB clock during register access while probing
  pwm: rockchip: rockchip_pwm_probe(): Remove superfluous
    clk_unprepare()
  pwm: rockchip: Replace "bus clk" with "PWM clk"
  pwm: rockchip: Eliminate potential race condition when probing
  pwm: rockchip: Enable clock before calling clk_get_rate()

 drivers/pwm/pwm-rockchip.c | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

-- 
2.30.0


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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v4 1/5] pwm: rockchip: Enable APB clock during register access while probing

[Simon South]

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 enabled, but did not also
change the function so it first enables 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(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 389a5e140412..e6929bc73968 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -330,9 +330,9 @@ 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 prepare enable APB clk: %d\n", ret);
 		goto err_clk;
 	}
 
@@ -362,10 +362,12 @@ 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);
 
-- 
2.30.0

[PATCH v4 1/5] pwm: rockchip: Enable APB clock during register access while probing

[Simon South]

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 enabled, but did not also
change the function so it first enables 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(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 389a5e140412..e6929bc73968 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -330,9 +330,9 @@ 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 prepare enable APB clk: %d\n", ret);
 		goto err_clk;
 	}
 
@@ -362,10 +362,12 @@ 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);
 
-- 
2.30.0


_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip

[PATCH v4 1/5] pwm: rockchip: Enable APB clock during register access while probing

[Simon South]

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 enabled, but did not also
change the function so it first enables 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(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 389a5e140412..e6929bc73968 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -330,9 +330,9 @@ 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 prepare enable APB clk: %d\n", ret);
 		goto err_clk;
 	}
 
@@ -362,10 +362,12 @@ 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);
 
-- 
2.30.0


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v4 2/5] pwm: rockchip: rockchip_pwm_probe(): Remove superfluous clk_unprepare()

[Simon South]

If rockchip_pwm_probe() fails to register a PWM device it calls
clk_unprepare() for the device's PWM clock, without having first disabled
the clock and before jumping to an error handler that also unprepares
it. This is likely to produce warnings from the kernel about the clock
being unprepared when it is still enabled, and then being unprepared when
it has already been unprepared.

Prevent these warnings by removing this unnecessary call to
clk_unprepare().

Fixes: 48cf973cae33 ("pwm: rockchip: Avoid glitches on already running PWMs")
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index e6929bc73968..90f969f9f5e2 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -351,7 +351,6 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 
 	ret = pwmchip_add(&pc->chip);
 	if (ret < 0) {
-		clk_unprepare(pc->clk);
 		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
 		goto err_pclk;
 	}
-- 
2.30.0

[PATCH v4 2/5] pwm: rockchip: rockchip_pwm_probe(): Remove superfluous clk_unprepare()

[Simon South]

If rockchip_pwm_probe() fails to register a PWM device it calls
clk_unprepare() for the device's PWM clock, without having first disabled
the clock and before jumping to an error handler that also unprepares
it. This is likely to produce warnings from the kernel about the clock
being unprepared when it is still enabled, and then being unprepared when
it has already been unprepared.

Prevent these warnings by removing this unnecessary call to
clk_unprepare().

Fixes: 48cf973cae33 ("pwm: rockchip: Avoid glitches on already running PWMs")
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index e6929bc73968..90f969f9f5e2 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -351,7 +351,6 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 
 	ret = pwmchip_add(&pc->chip);
 	if (ret < 0) {
-		clk_unprepare(pc->clk);
 		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
 		goto err_pclk;
 	}
-- 
2.30.0


_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip

[PATCH v4 2/5] pwm: rockchip: rockchip_pwm_probe(): Remove superfluous clk_unprepare()

[Simon South]

If rockchip_pwm_probe() fails to register a PWM device it calls
clk_unprepare() for the device's PWM clock, without having first disabled
the clock and before jumping to an error handler that also unprepares
it. This is likely to produce warnings from the kernel about the clock
being unprepared when it is still enabled, and then being unprepared when
it has already been unprepared.

Prevent these warnings by removing this unnecessary call to
clk_unprepare().

Fixes: 48cf973cae33 ("pwm: rockchip: Avoid glitches on already running PWMs")
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index e6929bc73968..90f969f9f5e2 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -351,7 +351,6 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 
 	ret = pwmchip_add(&pc->chip);
 	if (ret < 0) {
-		clk_unprepare(pc->clk);
 		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
 		goto err_pclk;
 	}
-- 
2.30.0


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v4 3/5] pwm: rockchip: Replace "bus clk" with "PWM clk"

[Simon South]

Clarify the Rockchip PWM driver's error messages by referring to the clock
that operates a PWM device as the "PWM" clock, matching its name in the
device tree, rather than the "bus" clock (which is especially misleading in
the case of devices that also use a separate clock for bus access).

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 90f969f9f5e2..b5bab427b5de 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -307,7 +307,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 		pc->clk = devm_clk_get(&pdev->dev, NULL);
 		if (IS_ERR(pc->clk))
 			return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk),
-					     "Can't get bus clk\n");
+					     "Can't get PWM clk\n");
 	}
 
 	count = of_count_phandle_with_args(pdev->dev.of_node,
@@ -326,7 +326,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 
 	ret = clk_prepare_enable(pc->clk);
 	if (ret) {
-		dev_err(&pdev->dev, "Can't prepare enable bus clk: %d\n", ret);
+		dev_err(&pdev->dev, "Can't prepare enable PWM clk: %d\n", ret);
 		return ret;
 	}
 
-- 
2.30.0

[PATCH v4 3/5] pwm: rockchip: Replace "bus clk" with "PWM clk"

[Simon South]

Clarify the Rockchip PWM driver's error messages by referring to the clock
that operates a PWM device as the "PWM" clock, matching its name in the
device tree, rather than the "bus" clock (which is especially misleading in
the case of devices that also use a separate clock for bus access).

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 90f969f9f5e2..b5bab427b5de 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -307,7 +307,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 		pc->clk = devm_clk_get(&pdev->dev, NULL);
 		if (IS_ERR(pc->clk))
 			return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk),
-					     "Can't get bus clk\n");
+					     "Can't get PWM clk\n");
 	}
 
 	count = of_count_phandle_with_args(pdev->dev.of_node,
@@ -326,7 +326,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 
 	ret = clk_prepare_enable(pc->clk);
 	if (ret) {
-		dev_err(&pdev->dev, "Can't prepare enable bus clk: %d\n", ret);
+		dev_err(&pdev->dev, "Can't prepare enable PWM clk: %d\n", ret);
 		return ret;
 	}
 
-- 
2.30.0


_______________________________________________
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Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip

[PATCH v4 3/5] pwm: rockchip: Replace "bus clk" with "PWM clk"

[Simon South]

Clarify the Rockchip PWM driver's error messages by referring to the clock
that operates a PWM device as the "PWM" clock, matching its name in the
device tree, rather than the "bus" clock (which is especially misleading in
the case of devices that also use a separate clock for bus access).

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 90f969f9f5e2..b5bab427b5de 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -307,7 +307,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 		pc->clk = devm_clk_get(&pdev->dev, NULL);
 		if (IS_ERR(pc->clk))
 			return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk),
-					     "Can't get bus clk\n");
+					     "Can't get PWM clk\n");
 	}
 
 	count = of_count_phandle_with_args(pdev->dev.of_node,
@@ -326,7 +326,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 
 	ret = clk_prepare_enable(pc->clk);
 	if (ret) {
-		dev_err(&pdev->dev, "Can't prepare enable bus clk: %d\n", ret);
+		dev_err(&pdev->dev, "Can't prepare enable PWM clk: %d\n", ret);
 		return ret;
 	}
 
-- 
2.30.0


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[PATCH v4 4/5] pwm: rockchip: Eliminate potential race condition when probing

[Simon South]

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>
---
 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 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);
-- 
2.30.0

[PATCH v4 4/5] pwm: rockchip: Eliminate potential race condition when probing

[Simon South]

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>
---
 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 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);
-- 
2.30.0


_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip

[PATCH v4 4/5] pwm: rockchip: Eliminate potential race condition when probing

[Simon South]

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>
---
 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 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);
-- 
2.30.0


_______________________________________________
linux-arm-kernel mailing list
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v4 5/5] pwm: rockchip: Enable clock before calling clk_get_rate()

[Simon South]

The documentation for clk_get_rate() in include/linux/clk.h states the
function's result is valid only for a clock source that has been
enabled. However, the Rockchip PWM driver uses this function in two places
to query the rate of a clock without first ensuring it is enabled.

Fix this by modifying rockchip_pwm_get_state() and rockchip_pwm_apply() so
they enable a device's PWM clock before querying its rate (in the latter
case, the querying is actually done in rockchip_pwm_config()) and disable
the clock again before returning.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 228147e9bc6e..6ad7d0a50aed 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -72,6 +72,10 @@ static void rockchip_pwm_get_state(struct pwm_chip *chip,
 	if (ret)
 		return;
 
+	ret = clk_enable(pc->clk);
+	if (ret)
+		return;
+
 	clk_rate = clk_get_rate(pc->clk);
 
 	tmp = readl_relaxed(pc->base + pc->data->regs.period);
@@ -90,6 +94,7 @@ static void rockchip_pwm_get_state(struct pwm_chip *chip,
 	else
 		state->polarity = PWM_POLARITY_NORMAL;
 
+	clk_disable(pc->clk);
 	clk_disable(pc->pclk);
 }
 
@@ -189,6 +194,10 @@ static int rockchip_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (ret)
 		return ret;
 
+	ret = clk_enable(pc->clk);
+	if (ret)
+		return ret;
+
 	pwm_get_state(pwm, &curstate);
 	enabled = curstate.enabled;
 
@@ -208,6 +217,7 @@ static int rockchip_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	}
 
 out:
+	clk_disable(pc->clk);
 	clk_disable(pc->pclk);
 
 	return ret;
-- 
2.30.0

[PATCH v4 5/5] pwm: rockchip: Enable clock before calling clk_get_rate()

[Simon South]

The documentation for clk_get_rate() in include/linux/clk.h states the
function's result is valid only for a clock source that has been
enabled. However, the Rockchip PWM driver uses this function in two places
to query the rate of a clock without first ensuring it is enabled.

Fix this by modifying rockchip_pwm_get_state() and rockchip_pwm_apply() so
they enable a device's PWM clock before querying its rate (in the latter
case, the querying is actually done in rockchip_pwm_config()) and disable
the clock again before returning.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 228147e9bc6e..6ad7d0a50aed 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -72,6 +72,10 @@ static void rockchip_pwm_get_state(struct pwm_chip *chip,
 	if (ret)
 		return;
 
+	ret = clk_enable(pc->clk);
+	if (ret)
+		return;
+
 	clk_rate = clk_get_rate(pc->clk);
 
 	tmp = readl_relaxed(pc->base + pc->data->regs.period);
@@ -90,6 +94,7 @@ static void rockchip_pwm_get_state(struct pwm_chip *chip,
 	else
 		state->polarity = PWM_POLARITY_NORMAL;
 
+	clk_disable(pc->clk);
 	clk_disable(pc->pclk);
 }
 
@@ -189,6 +194,10 @@ static int rockchip_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (ret)
 		return ret;
 
+	ret = clk_enable(pc->clk);
+	if (ret)
+		return ret;
+
 	pwm_get_state(pwm, &curstate);
 	enabled = curstate.enabled;
 
@@ -208,6 +217,7 @@ static int rockchip_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	}
 
 out:
+	clk_disable(pc->clk);
 	clk_disable(pc->pclk);
 
 	return ret;
-- 
2.30.0


_______________________________________________
Linux-rockchip mailing list
Linux-rockchip@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-rockchip

[PATCH v4 5/5] pwm: rockchip: Enable clock before calling clk_get_rate()

[Simon South]

The documentation for clk_get_rate() in include/linux/clk.h states the
function's result is valid only for a clock source that has been
enabled. However, the Rockchip PWM driver uses this function in two places
to query the rate of a clock without first ensuring it is enabled.

Fix this by modifying rockchip_pwm_get_state() and rockchip_pwm_apply() so
they enable a device's PWM clock before querying its rate (in the latter
case, the querying is actually done in rockchip_pwm_config()) and disable
the clock again before returning.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 228147e9bc6e..6ad7d0a50aed 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -72,6 +72,10 @@ static void rockchip_pwm_get_state(struct pwm_chip *chip,
 	if (ret)
 		return;
 
+	ret = clk_enable(pc->clk);
+	if (ret)
+		return;
+
 	clk_rate = clk_get_rate(pc->clk);
 
 	tmp = readl_relaxed(pc->base + pc->data->regs.period);
@@ -90,6 +94,7 @@ static void rockchip_pwm_get_state(struct pwm_chip *chip,
 	else
 		state->polarity = PWM_POLARITY_NORMAL;
 
+	clk_disable(pc->clk);
 	clk_disable(pc->pclk);
 }
 
@@ -189,6 +194,10 @@ static int rockchip_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (ret)
 		return ret;
 
+	ret = clk_enable(pc->clk);
+	if (ret)
+		return ret;
+
 	pwm_get_state(pwm, &curstate);
 	enabled = curstate.enabled;
 
@@ -208,6 +217,7 @@ static int rockchip_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	}
 
 out:
+	clk_disable(pc->clk);
 	clk_disable(pc->pclk);
 
 	return ret;
-- 
2.30.0


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Re: [PATCH v4 5/5] pwm: rockchip: Enable clock before calling clk_get_rate()

[Uwe Kleine-König]

[-- Attachment #1: Type: text/plain, Size: 1138 bytes --]

Hello Simon,

On Tue, Jan 19, 2021 at 11:12:09AM -0500, Simon South wrote:
> The documentation for clk_get_rate() in include/linux/clk.h states the
> function's result is valid only for a clock source that has been
> enabled. However, the Rockchip PWM driver uses this function in two places
> to query the rate of a clock without first ensuring it is enabled.
> 
> Fix this by modifying rockchip_pwm_get_state() and rockchip_pwm_apply() so
> they enable a device's PWM clock before querying its rate (in the latter
> case, the querying is actually done in rockchip_pwm_config()) and disable
> the clock again before returning.
> 
> Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Simon South <simon@simonsouth.net>

I already reviewed this patch in v3 and gave my

Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

You make it a bit easier if you add the received tags for new
iterations.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

[-- Attachment #2: signature.asc --]
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Re: [PATCH v4 5/5] pwm: rockchip: Enable clock before calling clk_get_rate()

[Uwe Kleine-König]

[-- Attachment #1.1: Type: text/plain, Size: 1138 bytes --]

Hello Simon,

On Tue, Jan 19, 2021 at 11:12:09AM -0500, Simon South wrote:
> The documentation for clk_get_rate() in include/linux/clk.h states the
> function's result is valid only for a clock source that has been
> enabled. However, the Rockchip PWM driver uses this function in two places
> to query the rate of a clock without first ensuring it is enabled.
> 
> Fix this by modifying rockchip_pwm_get_state() and rockchip_pwm_apply() so
> they enable a device's PWM clock before querying its rate (in the latter
> case, the querying is actually done in rockchip_pwm_config()) and disable
> the clock again before returning.
> 
> Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Simon South <simon@simonsouth.net>

I already reviewed this patch in v3 and gave my

Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

You make it a bit easier if you add the received tags for new
iterations.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[-- Attachment #2: Type: text/plain, Size: 170 bytes --]

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http://lists.infradead.org/mailman/listinfo/linux-rockchip

Re: [PATCH v4 5/5] pwm: rockchip: Enable clock before calling clk_get_rate()

[Uwe Kleine-König]

[-- Attachment #1.1: Type: text/plain, Size: 1138 bytes --]

Hello Simon,

On Tue, Jan 19, 2021 at 11:12:09AM -0500, Simon South wrote:
> The documentation for clk_get_rate() in include/linux/clk.h states the
> function's result is valid only for a clock source that has been
> enabled. However, the Rockchip PWM driver uses this function in two places
> to query the rate of a clock without first ensuring it is enabled.
> 
> Fix this by modifying rockchip_pwm_get_state() and rockchip_pwm_apply() so
> they enable a device's PWM clock before querying its rate (in the latter
> case, the querying is actually done in rockchip_pwm_config()) and disable
> the clock again before returning.
> 
> Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Simon South <simon@simonsouth.net>

I already reviewed this patch in v3 and gave my

Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

You make it a bit easier if you add the received tags for new
iterations.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

[-- Attachment #1.2: signature.asc --]
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[-- Attachment #2: Type: text/plain, Size: 176 bytes --]

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