linux-kernel - Re: [PATCH 1/2] i2c: sprd: Prevent i2c accesses after suspend is called

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Date:   Mon, 9 Apr 2018 15:56:52 -0500
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Baolin Wang <baolin.wang@...aro.org>, <wsa@...-dreams.de>
CC:     <broonie@...nel.org>, <linux-i2c@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] i2c: sprd: Prevent i2c accesses after suspend is
 called



On 04/09/2018 01:40 AM, Baolin Wang wrote:
> Add one flag to indicate if the i2c controller has been in suspend state,
> which can prevent i2c accesses after i2c controller is suspended following
> system suspend.

This usually indicates some bigger problem - there should be no i2c access to
 the I2C driver once it's suspended. But if happens - 
it means suspend dependencies between drivers are broken or there some 
scheduling primitives are not disabled properly.
(possible sources - kthreads, delayed works, timers or even threaded irqs)

> 
> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
> ---
>   drivers/i2c/busses/i2c-sprd.c |   16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-sprd.c b/drivers/i2c/busses/i2c-sprd.c
> index 25fcc3c..2fdad63 100644
> --- a/drivers/i2c/busses/i2c-sprd.c
> +++ b/drivers/i2c/busses/i2c-sprd.c
> @@ -86,6 +86,7 @@ struct sprd_i2c {
>   	u32 count;
>   	int irq;
>   	int err;
> +	bool is_suspended;
>   };
>   
>   static void sprd_i2c_set_count(struct sprd_i2c *i2c_dev, u32 count)
> @@ -283,6 +284,9 @@ static int sprd_i2c_master_xfer(struct i2c_adapter *i2c_adap,
>   	struct sprd_i2c *i2c_dev = i2c_adap->algo_data;
>   	int im, ret;
>   
> +	if (i2c_dev->is_suspended)
> +		return -EBUSY;
> +
>   	ret = pm_runtime_get_sync(i2c_dev->dev);
>   	if (ret < 0)
>   		return ret;
> @@ -586,11 +590,23 @@ static int sprd_i2c_remove(struct platform_device *pdev)
>   
>   static int __maybe_unused sprd_i2c_suspend_noirq(struct device *pdev)
>   {
> +	struct sprd_i2c *i2c_dev = dev_get_drvdata(pdev);
> +
> +	i2c_lock_adapter(&i2c_dev->adap);
> +	i2c_dev->is_suspended = true;
> +	i2c_unlock_adapter(&i2c_dev->adap);
> +
>   	return pm_runtime_force_suspend(pdev);
>   }
>   
>   static int __maybe_unused sprd_i2c_resume_noirq(struct device *pdev)
>   {
> +	struct sprd_i2c *i2c_dev = dev_get_drvdata(pdev);
> +
> +	i2c_lock_adapter(&i2c_dev->adap);
> +	i2c_dev->is_suspended = false;
> +	i2c_unlock_adapter(&i2c_dev->adap);
> +
>   	return pm_runtime_force_resume(pdev);
>   }
>   
> 

-- 
regards,
-grygorii