[PATCH 1/1] i2c: imx-lpi2c: avoid taking clk_prepare mutex in PM callbacks

[PATCH 1/1] i2c: imx-lpi2c: avoid taking clk_prepare mutex in PM callbacks

[Alexander Stein]

This is unsafe, as the runtime PM callbacks are called from the PM
workqueue, so this may deadlock when handling an i2c attached clock,
which may already hold the clk_prepare mutex from another context.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
---
This is the imx-lpi2c equivalent to commit d9a22d713acb ("i2c: imx: avoid
taking clk_prepare mutex in PM callbacks"). This patch needs to be used
together with [1] in order to fix the deadlock conditions.

Commit message is shamlessly taken from commit d9a22d713acb.

Best regards,
Alexander

[1] https://patchwork.ozlabs.org/project/linux-i2c/patch/20230310130815.562418-1-alexander.sverdlin@siemens.com/

 drivers/i2c/busses/i2c-imx-lpi2c.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index a49b14d52a98..1af0a637d7f1 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -639,7 +639,7 @@ static int __maybe_unused lpi2c_runtime_suspend(struct device *dev)
 {
 	struct lpi2c_imx_struct *lpi2c_imx = dev_get_drvdata(dev);
 
-	clk_bulk_disable_unprepare(lpi2c_imx->num_clks, lpi2c_imx->clks);
+	clk_bulk_disable(lpi2c_imx->num_clks, lpi2c_imx->clks);
 	pinctrl_pm_select_sleep_state(dev);
 
 	return 0;
@@ -651,7 +651,7 @@ static int __maybe_unused lpi2c_runtime_resume(struct device *dev)
 	int ret;
 
 	pinctrl_pm_select_default_state(dev);
-	ret = clk_bulk_prepare_enable(lpi2c_imx->num_clks, lpi2c_imx->clks);
+	ret = clk_bulk_enable(lpi2c_imx->num_clks, lpi2c_imx->clks);
 	if (ret) {
 		dev_err(dev, "failed to enable I2C clock, ret=%d\n", ret);
 		return ret;
-- 
2.34.1


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Re: [PATCH 1/1] i2c: imx-lpi2c: avoid taking clk_prepare mutex in PM callbacks

[Wolfram Sang]

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On Mon, Apr 24, 2023 at 10:06:27AM +0200, Alexander Stein wrote:
> This is unsafe, as the runtime PM callbacks are called from the PM
> workqueue, so this may deadlock when handling an i2c attached clock,
> which may already hold the clk_prepare mutex from another context.
> 
> Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>

Applied to for-current, thanks!


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