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From: Simon South <simon@simonsouth.net>
To: tpiepho@gmail.com, thierry.reding@gmail.com,
	u.kleine-koenig@pengutronix.de, robin.murphy@arm.com,
	lee.jones@linaro.org, heiko@sntech.de, bbrezillon@kernel.org,
	david.wu@rock-chips.com, steven.liu@rock-chips.com,
	linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Cc: simon@simonsouth.net
Subject: [PATCH v4 1/5] pwm: rockchip: Enable APB clock during register access while probing
Date: Tue, 19 Jan 2021 11:12:05 -0500	[thread overview]
Message-ID: <b16d8d5794235c469934c65a810ee00121be2acf.1610976129.git.simon@simonsouth.net> (raw)
In-Reply-To: <cover.1610976129.git.simon@simonsouth.net>

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


WARNING: multiple messages have this Message-ID (diff)
From: Simon South <simon@simonsouth.net>
To: tpiepho@gmail.com, thierry.reding@gmail.com,
	u.kleine-koenig@pengutronix.de, robin.murphy@arm.com,
	lee.jones@linaro.org, heiko@sntech.de, bbrezillon@kernel.org,
	david.wu@rock-chips.com, steven.liu@rock-chips.com,
	linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Cc: simon@simonsouth.net
Subject: [PATCH v4 1/5] pwm: rockchip: Enable APB clock during register access while probing
Date: Tue, 19 Jan 2021 11:12:05 -0500	[thread overview]
Message-ID: <b16d8d5794235c469934c65a810ee00121be2acf.1610976129.git.simon@simonsouth.net> (raw)
In-Reply-To: <cover.1610976129.git.simon@simonsouth.net>

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

WARNING: multiple messages have this Message-ID (diff)
From: Simon South <simon@simonsouth.net>
To: tpiepho@gmail.com, thierry.reding@gmail.com,
	u.kleine-koenig@pengutronix.de, robin.murphy@arm.com,
	lee.jones@linaro.org, heiko@sntech.de, bbrezillon@kernel.org,
	david.wu@rock-chips.com, steven.liu@rock-chips.com,
	linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Cc: simon@simonsouth.net
Subject: [PATCH v4 1/5] pwm: rockchip: Enable APB clock during register access while probing
Date: Tue, 19 Jan 2021 11:12:05 -0500	[thread overview]
Message-ID: <b16d8d5794235c469934c65a810ee00121be2acf.1610976129.git.simon@simonsouth.net> (raw)
In-Reply-To: <cover.1610976129.git.simon@simonsouth.net>

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

  reply	other threads:[~2021-01-19 16:14 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-19 16:12 [PATCH v4 0/5] pwm: rockchip: Eliminate potential race condition when probing Simon South
2021-01-19 16:12 ` Simon South
2021-01-19 16:12 ` Simon South
2021-01-19 16:12 ` Simon South [this message]
2021-01-19 16:12   ` [PATCH v4 1/5] pwm: rockchip: Enable APB clock during register access while probing Simon South
2021-01-19 16:12   ` Simon South
2021-01-19 16:12 ` [PATCH v4 2/5] pwm: rockchip: rockchip_pwm_probe(): Remove superfluous clk_unprepare() Simon South
2021-01-19 16:12   ` Simon South
2021-01-19 16:12   ` Simon South
2021-01-19 16:12 ` [PATCH v4 3/5] pwm: rockchip: Replace "bus clk" with "PWM clk" Simon South
2021-01-19 16:12   ` Simon South
2021-01-19 16:12   ` Simon South
2021-01-19 16:12 ` [PATCH v4 4/5] pwm: rockchip: Eliminate potential race condition when probing Simon South
2021-01-19 16:12   ` Simon South
2021-01-19 16:12   ` Simon South
2021-01-19 16:12 ` [PATCH v4 5/5] pwm: rockchip: Enable clock before calling clk_get_rate() Simon South
2021-01-19 16:12   ` Simon South
2021-01-19 16:12   ` Simon South
2021-01-19 19:22   ` Uwe Kleine-König
2021-01-19 19:22     ` Uwe Kleine-König
2021-01-19 19:22     ` Uwe Kleine-König

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