linux-kernel - Re: [PATCH v4 4/4] Input: atmel_mxt_ts

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Date: Fri, 21 Jun 2024 16:31:29 +0200
From: Stefan Eichenberger <eichest@...il.com>
To: Dmitry Torokhov <dmitry.torokhov@...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 4/4] Input: atmel_mxt_ts - add support for
 poweroff-sleep

Hi Dimitry,

On Wed, Jun 19, 2024 at 06:12:45PM -0700, Dmitry Torokhov wrote:
> Hi Stefan,
> 
> On Wed, Apr 17, 2024 at 11:05:27AM +0200, Stefan Eichenberger wrote:
> > From: Stefan Eichenberger <stefan.eichenberger@...adex.com>
> > 
> > Add support for poweroff-sleep to the Atmel maXTouch driver. This allows
> > us to power off the input device entirely and only power it on when it
> > is opened. This will also automatically power it off when we suspend the
> > system.
> > 
> > Signed-off-by: Stefan Eichenberger <stefan.eichenberger@...adex.com>
> > ---
> >  drivers/input/touchscreen/atmel_mxt_ts.c | 71 +++++++++++++++++++-----
> >  1 file changed, 57 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
> > index 7c807d1f1f9b..f92808be3f5b 100644
> > --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> > +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> > @@ -317,6 +317,7 @@ struct mxt_data {
> >  	struct gpio_desc *reset_gpio;
> >  	struct gpio_desc *wake_gpio;
> >  	bool use_retrigen_workaround;
> > +	bool poweroff_sleep;
> 
> Why is this separate from "enum mxt_suspend_mode suspend_mode"? Can we
> make MXT_SUSPEND_POWEROFF and use it in mxt_start() and others? It still
> can be driven by the "atmel,poweroff-sleep" device property. 

I agree and will change this in the next version.

> >  
> >  	/* Cached parameters from object table */
> >  	u16 T5_address;
> > @@ -2277,6 +2278,19 @@ static void mxt_config_cb(const struct firmware *cfg, void *ctx)
> >  	release_firmware(cfg);
> >  }
> >  
> > +static int mxt_initialize_after_resume(struct mxt_data *data)
> > +{
> > +	const struct firmware *fw;
> > +
> > +	mxt_acquire_irq(data);
> > +
> > +	firmware_request_nowarn(&fw, MXT_CFG_NAME, &data->client->dev);
> > +
> > +	mxt_config_cb(fw, data);
> 
> Is this really required? As far as I know all maXTouch controllers have
> NVRAM for their configs and should not lose configuration even if power
> is cut off. In fact, the whole automatic request of firmware/config upon
> probe I think was a mistake and I would like to get rid of it. In fact,
> on Chrome OS the version of the driver in use does not do that and
> instead relies on userspace to check if firmware update is needed.
> 
> If this is actually required you need to add error handling.

You are right, and the configuration goes to non-volatile memory, so
this is not needed. I will remove the firmware loading here and improve
the error handling. I will keep the firmware loading in the initial
probe for now, to be consistent with the non poweroff-sleep version.

Regards,
Stefan