linux-kernel - Re: [PATCH v4 1/4] Input: atmel_mxt_ts - add power off and power on functions

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Message-ID: <ZnRMxONryyi5uZ8a@google.com>
Date: Thu, 20 Jun 2024 08:37:40 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Stefan Eichenberger <eichest@...il.com>
Cc: nick@...anahar.org, robh@...nel.org, krzysztof.kozlowski+dt@...aro.org,
	conor+dt@...nel.org, nicolas.ferre@...rochip.com,
	alexandre.belloni@...tlin.com, claudiu.beznea@...on.dev,
	linus.walleij@...aro.org, linux-input@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Stefan Eichenberger <stefan.eichenberger@...adex.com>
Subject: Re: [PATCH v4 1/4] Input: atmel_mxt_ts - add power off and power on
 functions

Hi Stefan,

On Wed, Apr 17, 2024 at 11:05:24AM +0200, Stefan Eichenberger wrote:
> From: Stefan Eichenberger <stefan.eichenberger@...adex.com>
> 
> Add a separate function for power off and power on instead of calling
> regulator_bulk_enable and regulator_bulk_disable directly.
> 
> Signed-off-by: Stefan Eichenberger <stefan.eichenberger@...adex.com>
> ---
>  drivers/input/touchscreen/atmel_mxt_ts.c | 59 +++++++++++++++---------
>  1 file changed, 37 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> index 542a31448c8f..52867ce3b9b6 100644
> --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> @@ -1307,6 +1307,38 @@ static int mxt_soft_reset(struct mxt_data *data)
>  	return 0;
>  }
>  
> +static int mxt_power_on(struct mxt_data *data)
> +{
> +	int error;
> +
> +	error = regulator_bulk_enable(ARRAY_SIZE(data->regulators),
> +				      data->regulators);
> +	if (error) {
> +		dev_err(&data->client->dev, "failed to enable regulators: %d\n",
> +			error);
> +		return error;
> +	}
> +
> +	msleep(MXT_BACKUP_TIME);
> +
> +	if (data->reset_gpio) {
> +		/* Wait a while and then de-assert the RESET GPIO line */
> +		msleep(MXT_RESET_GPIO_TIME);
> +		gpiod_set_value(data->reset_gpio, 0);
> +		msleep(MXT_RESET_INVALID_CHG);
> +	}
> +
> +	return 0;
> +}
> +
> +static void mxt_power_off(struct mxt_data *data)
> +{
> +	if (data->reset_gpio)
> +		gpiod_set_value(data->reset_gpio, 1);
> +
> +	regulator_bulk_disable(ARRAY_SIZE(data->regulators), data->regulators);
> +}
> +
>  static void mxt_update_crc(struct mxt_data *data, u8 cmd, u8 value)
>  {
>  	/*
> @@ -3305,25 +3337,9 @@ static int mxt_probe(struct i2c_client *client)
>  		return error;
>  	}
>  
> -	error = regulator_bulk_enable(ARRAY_SIZE(data->regulators),
> -				      data->regulators);
> -	if (error) {
> -		dev_err(&client->dev, "failed to enable regulators: %d\n",
> -			error);
> +	error = mxt_power_on(data);
> +	if (error)
>  		return error;
> -	}
> -	/*
> -	 * The device takes 40ms to come up after power-on according
> -	 * to the mXT224 datasheet, page 13.
> -	 */
> -	msleep(MXT_BACKUP_TIME);
> -
> -	if (data->reset_gpio) {
> -		/* Wait a while and then de-assert the RESET GPIO line */
> -		msleep(MXT_RESET_GPIO_TIME);
> -		gpiod_set_value(data->reset_gpio, 0);
> -		msleep(MXT_RESET_INVALID_CHG);
> -	}
>  
>  	/*
>  	 * Controllers like mXT1386 have a dedicated WAKE line that could be
> @@ -3361,8 +3377,8 @@ static int mxt_probe(struct i2c_client *client)
>  	mxt_free_input_device(data);
>  	mxt_free_object_table(data);
>  err_disable_regulators:
> -	regulator_bulk_disable(ARRAY_SIZE(data->regulators),
> -			       data->regulators);
> +	mxt_power_off(data);
> +
>  	return error;
>  }
>  
> @@ -3374,8 +3390,7 @@ static void mxt_remove(struct i2c_client *client)
>  	sysfs_remove_group(&client->dev.kobj, &mxt_attr_group);
>  	mxt_free_input_device(data);
>  	mxt_free_object_table(data);
> -	regulator_bulk_disable(ARRAY_SIZE(data->regulators),
> -			       data->regulators);
> +	mxt_power_off(data);

This change means that on unbind we will leave with GPIO line asserted.
Won't this potentially cause some current leakage? Why do we need to
have reset asserted here?

Thanks.

-- 
Dmitry