linux-kernel - Re: [PATCH] Input: matrix_keypad

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Date:   Sun, 4 Feb 2018 00:31:29 +0800 (CST)
From:   "Zhang Bo" <zbsdta@....com>
To:     "Marcus Folkesson" <marcus.folkesson@...il.com>
Cc:     dmitry.torokhov@...il.com, DRivshin@...worx.com, robh@...nel.org,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        zhang.bo19@....com.cn
Subject: Re: [PATCH] Input: matrix_keypad - fix keypad does not response

At 2018-02-03 21:44:50, "Marcus Folkesson" <marcus.folkesson@...il.com> wrote:
>> diff --git a/drivers/input/keyboard/matrix_keypad.c b/drivers/input/keyboard/matrix_keypad.c
>> index 1f316d66e6f7..13fe51824637 100644
>> --- a/drivers/input/keyboard/matrix_keypad.c
>> +++ b/drivers/input/keyboard/matrix_keypad.c
>> @@ -169,7 +169,8 @@ static void matrix_keypad_scan(struct work_struct *work)
>>  	/* Enable IRQs again */
>>  	spin_lock_irq(&keypad->lock);
>>  	keypad->scan_pending = false;
>> -	enable_row_irqs(keypad);
>> +	if (keypad->stopped == false)
>> +		enable_row_irqs(keypad);
>>  	spin_unlock_irq(&keypad->lock);
>>  }
>>  
>> @@ -202,14 +203,16 @@ static int matrix_keypad_start(struct input_dev *dev)
>>  {
>>  	struct matrix_keypad *keypad = input_get_drvdata(dev);
>>  
>> +	spin_lock_irq(&keypad->lock);
>>  	keypad->stopped = false;
>> -	mb();
>>  
>>  	/*
>>  	 * Schedule an immediate key scan to capture current key state;
>>  	 * columns will be activated and IRQs be enabled after the scan.
>>  	 */
>> -	schedule_delayed_work(&keypad->work, 0);
>> +	if (keypad->scan_pending == false)
>> +		schedule_delayed_work(&keypad->work, 0);
>> +	spin_unlock_irq(&keypad->lock);
>>  
>>  	return 0;
>>  }
>> @@ -218,14 +221,17 @@ static void matrix_keypad_stop(struct input_dev *dev)
>>  {
>>  	struct matrix_keypad *keypad = input_get_drvdata(dev);
>>  
>> +	spin_lock_irq(&keypad->lock);
>>  	keypad->stopped = true;
>> -	mb();
>> -	flush_work(&keypad->work.work);
>>  	/*
>>  	 * matrix_keypad_scan() will leave IRQs enabled;
>>  	 * we should disable them now.
>>  	 */
>> -	disable_row_irqs(keypad);
>> +	if (keypad->scan_pending == false)
>> +		disable_row_irqs(keypad);
>> +	spin_unlock_irq(&keypad->lock);
>> +
>> +	flush_work(&keypad->work.work);
>>  }
>
>
>Hum, I think we should use spin_lock_irqsave/spin_lock_irqrestore
>instead to be on the safe side. 
>I don't see how we could guarantee that irqs is allways enabled when
>calling spin_lock_irq().

spin_lock_irq and  spin_unlock_irq are called in matrix_keypad_stop and matrix_keypad_start
which are in suspend and resume,  they run in process context, matrix_keypad_scan runs in
worker which is in process context also.