linux-kernel - Re: [PATCH] i2c: stm32f7: Fix runtime PM imbalance in stm32f7_i2c_reg

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Date:   Tue, 26 May 2020 10:34:00 +0200
From:   Alain Volmat <alain.volmat@...com>
To:     Dinghao Liu <dinghao.liu@....edu.cn>
CC:     <kjlu@....edu>, Pierre-Yves MORDRET <pierre-yves.mordret@...com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        <linux-i2c@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: stm32f7: Fix runtime PM imbalance in
 stm32f7_i2c_reg_slave

Hi Dinghao,

Thanks for the patch. Indeed, this should be fixed.

Overall, there are several other calls to pm_runtime_get_sync within this
driver, would you like to fix them all at once ?

On Thu, May 21, 2020 at 03:05:07PM +0800, Dinghao Liu wrote:
> pm_runtime_get_sync() increments the runtime PM usage counter even
> the call returns an error code. Thus a pairing decrement is needed
> on the error handling path to keep the counter balanced.
> 
> Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> ---
>  drivers/i2c/busses/i2c-stm32f7.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
> index 330ffed011e0..602cf35649c8 100644
> --- a/drivers/i2c/busses/i2c-stm32f7.c
> +++ b/drivers/i2c/busses/i2c-stm32f7.c
> @@ -1767,8 +1767,10 @@ static int stm32f7_i2c_reg_slave(struct i2c_client *slave)
>  		return ret;
>  
>  	ret = pm_runtime_get_sync(dev);
> -	if (ret < 0)
> +	if (ret < 0) {
> +		pm_runtime_put_autosuspend(dev);

Considering that if we fail here there is a very good chance that this is due
to the resume failing, pm_runtime_put_noidle would probably make more sense
since pm_runtime_put_autosuspend will most probably fail as well.

>  		return ret;
> +	}
>  
>  	if (!stm32f7_i2c_is_slave_registered(i2c_dev))
>  		stm32f7_i2c_enable_wakeup(i2c_dev, true);
> -- 
> 2.17.1
>