linux-kernel - Re: [PATCH v5 6/7] Input: matrix_keypad - add settle time after enable all columns

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Message-ID: <Z7YLPRfOMzeTj9UU@mt.com>
Date: Wed, 19 Feb 2025 17:47:57 +0100
From: Manuel Traut <manuel.traut@...com>
To: Markus Burri <markus.burri@...com>
Cc: linux-kernel@...r.kernel.org,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Marek Vasut <marek.vasut@...il.com>, linux-input@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v5 6/7] Input: matrix_keypad - add settle time after
 enable all columns

On Fri, Jan 10, 2025 at 06:49:05AM +0100, Markus Burri wrote:
> Matrix_keypad with high capacity need a longer settle time after enable

matrix keypads with a high capacity need a longer settle time after enable

> all columns and re-enabling interrupts.

> This to give time stable the system and not generate interrupts.
It avoids spurios interrupts by giving the system time to stable.
 
> Add a new optional device-tree property to configure the time before
> enabling interrupts after disable all columns.
> The default is no delay.

The delay for re-enabling the interrupts can be configured by a
device-tree property. The default is no delay.

> Signed-off-by: Markus Burri <markus.burri@...com>

Reviewed-by: Manuel Traut <manuel.traut@...com>

> ---
>  drivers/input/keyboard/matrix_keypad.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/input/keyboard/matrix_keypad.c b/drivers/input/keyboard/matrix_keypad.c
> index 90148d3..fdb3499 100644
> --- a/drivers/input/keyboard/matrix_keypad.c
> +++ b/drivers/input/keyboard/matrix_keypad.c
> @@ -26,6 +26,7 @@ struct matrix_keypad {
>  	unsigned int row_shift;
>  
>  	unsigned int col_scan_delay_us;
> +	unsigned int all_cols_on_delay_us;
>  	/* key debounce interval in milli-second */
>  	unsigned int debounce_ms;
>  	bool drive_inactive_cols;
> @@ -77,6 +78,9 @@ static void activate_all_cols(struct matrix_keypad *keypad, bool on)
>  
>  	for (col = 0; col < keypad->num_col_gpios; col++)
>  		__activate_col(keypad, col, on);
> +
> +	if (on && keypad->all_cols_on_delay_us)
> +		fsleep(keypad->all_cols_on_delay_us);
>  }
>  
>  static bool row_asserted(struct matrix_keypad *keypad, int row)
> @@ -400,6 +404,8 @@ static int matrix_keypad_probe(struct platform_device *pdev)
>  				 &keypad->debounce_ms);
>  	device_property_read_u32(&pdev->dev, "col-scan-delay-us",
>  				 &keypad->col_scan_delay_us);
> +	device_property_read_u32(&pdev->dev, "all-cols-on-delay-us",
> +				 &keypad->all_cols_on_delay_us);
>  
>  	err = matrix_keypad_init_gpio(pdev, keypad);
>  	if (err)
> -- 
> 2.39.5
>