Hi Marek,
thanks a lot for the patch.
On Sat, Sep 28, 2024 at 03:43:46AM +0200, Marek Vasut wrote:
> In case there is any sort of clock controller attached to this I2C bus
> controller, for example Versaclock or even an AIC32x4 I2C codec, then
> an I2C transfer triggered from the clock controller clk_ops .prepare
> callback may trigger a deadlock on drivers/clk/clk.c prepare_lock mutex.
>
> This is because the clock controller first grabs the prepare_lock mutex
> and then performs the prepare operation, including its I2C access. The
> I2C access resumes this I2C bus controller via .runtime_resume callback,
> which calls clk_prepare_enable(), which attempts to grab the prepare_lock
> mutex again and deadlocks.
>
> Since the clock are already prepared since probe() and unprepared in
> remove(), use simple clk_enable()/clk_disable() calls to enable and
> disable the clock on runtime suspend and resume, to avoid hitting the
> prepare_lock mutex.
>
> Signed-off-by: Marek Vasut <marex@xxxxxxx>
> ---
> Cc: Alain Volmat <alain.volmat@xxxxxxxxxxx>
> Cc: Alexandre Torgue <alexandre.torgue@xxxxxxxxxxx>
> Cc: Andi Shyti <andi.shyti@xxxxxxxxxx>
> Cc: Christoph Niedermaier <cniedermaier@xxxxxxxxxxxxxxxxxx>
> Cc: Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>
> Cc: Pierre-Yves MORDRET <pierre-yves.mordret@xxxxxxxxxxx>
> Cc: kernel@xxxxxxxxxxxxxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-i2c@xxxxxxxxxxxxxxx
> Cc: linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
> ---
> drivers/i2c/busses/i2c-stm32f7.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
> index cfee2d9c09de3..65c035728a4fa 100644
> --- a/drivers/i2c/busses/i2c-stm32f7.c
> +++ b/drivers/i2c/busses/i2c-stm32f7.c
> @@ -2395,7 +2395,7 @@ static int __maybe_unused stm32f7_i2c_runtime_suspend(struct device *dev)
> struct stm32f7_i2c_dev *i2c_dev = dev_get_drvdata(dev);
>
> if (!stm32f7_i2c_is_slave_registered(i2c_dev))
> - clk_disable_unprepare(i2c_dev->clk);
> + clk_disable(i2c_dev->clk);
>
> return 0;
> }
> @@ -2406,7 +2406,7 @@ static int __maybe_unused stm32f7_i2c_runtime_resume(struct device *dev)
> int ret;
>
> if (!stm32f7_i2c_is_slave_registered(i2c_dev)) {
> - ret = clk_prepare_enable(i2c_dev->clk);
> + ret = clk_enable(i2c_dev->clk);
> if (ret) {
> dev_err(dev, "failed to prepare_enable clock\n");
The call now being clk_enable, could you also change the error message
from prepare_enable to enable ?
With that done,
Acked-by: Alain Volmat <alain.volmat@xxxxxxxxxxx>
Regards,
Alain
> return ret;
> --
> 2.45.2
>
