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From:   =?utf-8?B?UGF3ZcWC?= Chmiel <pawel.mikolaj.chmiel@gmail.com>
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc:     nick@shmanahar.org, robh+dt@kernel.org, mark.rutland@arm.com,
        nicolas.ferre@microchip.com, alexandre.belloni@bootlin.com,
        linux-input@vger.kernel.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] Input: atmel_mxt_ts: Add support for optional regulators.
Date:   Tue, 17 Jul 2018 18:08:09 +0200
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On Sunday, July 15, 2018 10:25:47 AM CEST Dmitry Torokhov wrote:
> Hi Pawe=C5=82,
>=20
> On Fri, Jul 13, 2018 at 08:30:07PM +0200, Pawe=C5=82 Chmiel wrote:
> > This patch adds optional regulators, which can be used to power
> > up touchscreen. After enabling regulators, we need to wait 150msec.
> > This value is taken from official driver.
> >=20
> > It was tested on Samsung Galaxy i9000 (based on Samsung S5PV210 SOC).
> >=20
> > Signed-off-by: Pawe=C5=82 Chmiel <pawel.mikolaj.chmiel@gmail.com>
> > ---
> >  drivers/input/touchscreen/atmel_mxt_ts.c | 45 ++++++++++++++++++++++++=
++++++++
> >  1 file changed, 45 insertions(+)
> >=20
> > diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/t=
ouchscreen/atmel_mxt_ts.c
> > index 54fe190fd4bc..a7625ec8fb9f 100644
> > --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> > +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> > @@ -27,6 +27,7 @@
> >  #include <linux/interrupt.h>
> >  #include <linux/of.h>
> >  #include <linux/property.h>
> > +#include <linux/regulator/consumer.h>
> >  #include <linux/slab.h>
> >  #include <linux/gpio/consumer.h>
> >  #include <linux/property.h>
> > @@ -198,6 +199,7 @@ enum t100_type {
> >  #define MXT_RESET_INVALID_CHG	100	/* msec */
> >  #define MXT_RESET_TIME		200	/* msec */
> >  #define MXT_RESET_TIMEOUT	3000	/* msec */
> > +#define MXT_REGULATOR_DELAY	150	/* msec */
> >  #define MXT_CRC_TIMEOUT		1000	/* msec */
> >  #define MXT_FW_RESET_TIME	3000	/* msec */
> >  #define MXT_FW_CHG_TIMEOUT	300	/* msec */
> > @@ -310,6 +312,8 @@ struct mxt_data {
> >  	struct t7_config t7_cfg;
> >  	struct mxt_dbg dbg;
> >  	struct gpio_desc *reset_gpio;
> > +	struct regulator *vdd_reg;
> > +	struct regulator *avdd_reg;
> > =20
> >  	/* Cached parameters from object table */
> >  	u16 T5_address;
> > @@ -3076,6 +3080,40 @@ static int mxt_probe(struct i2c_client *client, =
const struct i2c_device_id *id)
> >  		return error;
> >  	}
> > =20
> > +	data->vdd_reg =3D devm_regulator_get_optional(&client->dev, "vdd");
> > +	if (IS_ERR(data->vdd_reg)) {
> > +		error =3D PTR_ERR(data->vdd_reg);
> > +		dev_err(&client->dev, "Failed to get vdd regulator: %d\n",
> > +			error);
> > +		return error;
> > +	}
> > +
> > +	if (data->vdd_reg) {
> > +		error =3D regulator_enable(data->vdd_reg);
> > +		if (error) {
> > +			dev_err(&client->dev, "Failed to enable vdd regulator: %d\n",
> > +				error);
> > +			return error;
> > +		}
> > +	}
> > +
> > +	data->avdd_reg =3D devm_regulator_get_optional(&client->dev, "avdd");
> > +	if (IS_ERR(data->avdd_reg)) {
> > +		error =3D PTR_ERR(data->avdd_reg);
> > +		dev_err(&client->dev, "Failed to get avdd regulator: %d\n",
> > +			error);
> > +		return error;
> > +	}
> > +
> > +	if (data->avdd_reg) {
>=20
> devm_regulator_get_optional() does not return NULL for regulators
> not present in device tree, but rather -ENOENT, so this code is not
> correct; neither is the simple IS_ERR() check above.
>=20
> Moreover, the optional regulators should be used when there is a part of
> IP block that can be optionally powered up, but the device can work
> (with limited functionality) even when it is powered down. They should
> not be used in cases when supplies are mandatory (such as vdd/avdd) but
> may not be exposed to the kernel by the firmware.
>=20
> Simply use devm_regulator_get() and rely on the fact that on fully
> constrained system you will get a dummy regulator.
>=20
> > +		error =3D regulator_enable(data->avdd_reg);
> > +		if (error) {
> > +			dev_err(&client->dev, "Failed to enable avdd regulator: %d\n",
> > +				error);
> > +			return error;
> > +		}
> > +	}
> > +
> >  	error =3D devm_request_threaded_irq(&client->dev, client->irq,
> >  					  NULL, mxt_interrupt, IRQF_ONESHOT,
> >  					  client->name, data);
> > @@ -3086,6 +3124,9 @@ static int mxt_probe(struct i2c_client *client, c=
onst struct i2c_device_id *id)
> > =20
> >  	disable_irq(client->irq);
> > =20
> > +	if (!IS_ERR(data->vdd_reg) || !IS_ERR(data->avdd_reg))
> > +		msleep(MXT_REGULATOR_DELAY);
> > +
> >  	if (data->reset_gpio) {
>=20
> I think you should require that if regulators are exposed then reset
> gpio should also be present to ensure proper power up timings.

Thanks for comments. I'll prepare v2 version with those changes applied.
>=20
> >  		msleep(MXT_RESET_GPIO_TIME);
> >  		gpiod_set_value(data->reset_gpio, 1);
> > @@ -3116,6 +3157,10 @@ static int mxt_remove(struct i2c_client *client)
> >  	struct mxt_data *data =3D i2c_get_clientdata(client);
> > =20
> >  	disable_irq(data->irq);
> > +	if (!IS_ERR(data->avdd_reg))
> > +		regulator_disable(data->avdd_reg);
> > +	if (!IS_ERR(data->vdd_reg))
> > +		regulator_disable(data->vdd_reg);
> >  	sysfs_remove_group(&client->dev.kobj, &mxt_attr_group);
> >  	mxt_free_input_device(data);
> >  	mxt_free_object_table(data);
>=20
> Thanks.
>=20
>=20