linux-kernel - Re: [PATCH v2] Input: atmel_mxt_ts

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Date:   Fri, 27 Sep 2019 17:16:26 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Evan Green <evgreen@...omium.org>
Cc:     Nick Dyer <nick@...anahar.org>,
        Jongpil Jung <jongpil19.jung@...sung.com>,
        Furquan Shaikh <furquan@...omium.org>,
        Rajat Jain <rajatja@...omium.org>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH v2] Input: atmel_mxt_ts - Disable IRQ across suspend

Hi Evan,

On Tue, Sep 24, 2019 at 02:52:38PM -0700, Evan Green wrote:
> Across suspend and resume, we are seeing error messages like the following:
> 
> atmel_mxt_ts i2c-PRP0001:00: __mxt_read_reg: i2c transfer failed (-121)
> atmel_mxt_ts i2c-PRP0001:00: Failed to read T44 and T5 (-121)
> 
> This occurs because the driver leaves its IRQ enabled. Upon resume, there
> is an IRQ pending, but the interrupt is serviced before both the driver and
> the underlying I2C bus have been resumed. This causes EREMOTEIO errors.
> 
> Disable the IRQ in suspend, and re-enable it on resume. If there are cases
> where the driver enters suspend with interrupts disabled, that's a bug we
> should fix separately.
> 
> Signed-off-by: Evan Green <evgreen@...omium.org>
> ---
> 
> Changes in v2:
>  - Enable and disable unconditionally (Dmitry)
> 
>  drivers/input/touchscreen/atmel_mxt_ts.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> index 24c4b691b1c9..a58092488679 100644
> --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> @@ -3155,6 +3155,7 @@ static int __maybe_unused mxt_suspend(struct device *dev)
>  		mxt_stop(data);
>  
>  	mutex_unlock(&input_dev->mutex);
> +	disable_irq(data->irq);
>  
>  	return 0;
>  }
> @@ -3174,6 +3175,7 @@ static int __maybe_unused mxt_resume(struct device *dev)
>  		mxt_start(data);
>  
>  	mutex_unlock(&input_dev->mutex);
> +	enable_irq(data->irq);

At least for older devices that do soft reset on resume we need
interrupts to already work when we call mxt_start().

In general, order of resume steps should mirror suspend.

Thanks.

-- 
Dmitry