Date:   Wed, 22 Aug 2018 18:53:21 -0400
From:   "George G. Davis" <ggdavisiv@...il.com>
To:     Nick Dyer <nick@...anahar.org>
Cc:     Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>,
        mark.rutland@....com, devicetree@...r.kernel.org,
        alexandre.belloni@...tlin.com, dmitry.torokhov@...il.com,
        linux-kernel@...r.kernel.org, robh+dt@...nel.org,
        linux-input@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] Input: atmel_mxt_ts: Add support for  optional
 regulators.

Hello Nick,

On Tue, Jul 17, 2018 at 10:00:05PM +0100, 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@...il.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 )

I'm actually quite interested in your work and notice that it has
languished for some time now. If you have rebased any of your earlier
work to more recent kernel versions, I'd be happy to assist with testing
and review.

--
Regards,
George

> 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.
> 
> 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);
> > -- 
> > 2.7.4
> > 
> 
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