Re: [PATCH v2 1/2] Input: atmel_mxt_ts: Add support for optional regulators.

["Paweł Chmiel" <pawel.mikolaj.chmiel@gmail.com>]

On Tuesday, July 17, 2018 10:00:05 PM CEST Nick Dyer wrote:
> On Tue, Jul 17, 2018 at 08:16:25PM +0200, Paweł 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.
> > 
> > It was tested on Samsung Galaxy i9000 (based on Samsung S5PV210 SOC).
> > 
> > Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
> > ---
> > Changes from v1:
> >   - Enable regulators only if reset_gpio is present.
> >   - Switch from devm_regulator_get_optional to devm_regulator_get
> > ---
> >  drivers/input/touchscreen/atmel_mxt_ts.c | 46 ++++++++++++++++++++++++++++++--
> >  1 file changed, 44 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> > index 54fe190fd4bc..005f0fee9fc8 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>
> > @@ -194,10 +195,10 @@ enum t100_type {
> >  
> >  /* Delay times */
> >  #define MXT_BACKUP_TIME		50	/* msec */
> > -#define MXT_RESET_GPIO_TIME	20	/* msec */
> >  #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 +311,8 @@ 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;
> >  
> >  	/* Cached parameters from object table */
> >  	u16 T5_address;
> > @@ -3076,6 +3079,22 @@ static int mxt_probe(struct i2c_client *client, const struct i2c_device_id *id)
> >  		return error;
> >  	}
> >  
> > +	data->vdd_reg = devm_regulator_get(&client->dev, "vdd");
> > +	if (IS_ERR(data->vdd_reg)) {
> > +		error = PTR_ERR(data->vdd_reg);
> > +		dev_err(&client->dev, "Failed to get vdd regulator: %d\n",
> > +			error);
> > +		return error;
> > +	}
> > +
> > +	data->avdd_reg = devm_regulator_get(&client->dev, "avdd");
> > +	if (IS_ERR(data->avdd_reg)) {
> > +		error = PTR_ERR(data->avdd_reg);
> > +		dev_err(&client->dev, "Failed to get avdd regulator: %d\n",
> > +			error);
> > +		return error;
> > +	}
> > +
> >  	error = devm_request_threaded_irq(&client->dev, client->irq,
> >  					  NULL, mxt_interrupt, IRQF_ONESHOT,
> >  					  client->name, data);
> > @@ -3087,7 +3106,26 @@ static int mxt_probe(struct i2c_client *client, const struct i2c_device_id *id)
> >  	disable_irq(client->irq);
> >  
> >  	if (data->reset_gpio) {
> > -		msleep(MXT_RESET_GPIO_TIME);
> > +		error = regulator_enable(data->vdd_reg);
> > +		if (error) {
> > +			dev_err(&client->dev, "Failed to enable vdd regulator: %d\n",
> > +				error);
> > +			return error;
> > +		}
> > +
> > +		error = regulator_enable(data->avdd_reg);
> > +		if (error) {
> > +			dev_err(&client->dev, "Failed to enable avdd regulator: %d\n",
> > +				error);
> > +			return error;
> > +		}
> > +
> > +		/*
> > +		 * According to maXTouch power sequencing specification, RESET line
> > +		 * must be kept low until some time after regulators come up to
> > +		 * voltage
> > +		 */
> > +		msleep(MXT_REGULATOR_DELAY);
> >  		gpiod_set_value(data->reset_gpio, 1);
> >  		msleep(MXT_RESET_INVALID_CHG);
> 
> Hi Pawel-
> 
> I see you've borrowed some of the logic from the patch I wrote a while
> back (see https://github.com/ndyer/linux/commit/8e9687e41ed062 )
Actually, i was looking at https://github.com/atmel-maxtouch/linux/blob/maxtouch-v3.14/drivers/input/touchscreen/atmel_mxt_ts.c (and didn't saw Your patch till now).
Are You going to submit it? (it has more functionalities - for example suspend mode read from device tree).
> 
> The correct behaviour according to Atmel should be:
> 
> * Make RESET zero
> * Bring up regulators
> * Wait for a period to settle (150 msec)
> * Release RESET
> * Wait for 100 msec whilst device gets through bootloader
> * Wait for CHG line assert before reading info block
> 
> I can't see the first and last steps in your patch at present.
About first step - reset_gpio is readed by using devm_gpiod_get_optional with GPIOD_OUT_LOW flag, so i think (but might be wrong)  that we don't need to set this gpio value again to 0 before enabling regulators,
since currently only place where reset_gpio is used is in driver probe (in Your patch it is used in other cases/places - for example in mxt_start/stop, when we enable regulators).
About missing wait after releasing reset, shouldn't this be separate patch (since currently driver is not doing it)? I can prepare it and send with other in next version.

Thanks for feedback
> 
> The only downside with this approach is that there are a lot of
> delays during driver probe, but I believe the asynchronous probe stuff
> that's landed since I wrote the original patch should address that.
> 
> cheers
> 
> Nick
> 
> >  	}
> > @@ -3116,6 +3154,10 @@ static int mxt_remove(struct i2c_client *client)
> >  	struct mxt_data *data = i2c_get_clientdata(client);
> >  
> >  	disable_irq(data->irq);
> > +	if (data->reset_gpio) {
> > +		regulator_disable(data->avdd_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);
>