linux-kernel - Re: [PATCH v3 2/2] HID: i2c-hid: support regulator power on/off

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Date:   Thu, 1 Dec 2016 17:16:15 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Caesar Wang <wxt@...k-chips.com>,
        linux-rockchip@...ts.infradead.org,
        Rob Herring <robh+dt@...nel.org>, linux-input@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Doug Anderson <dianders@...omium.org>
Subject: Re: [PATCH v3 2/2] HID: i2c-hid: support regulator power on/off

On Thu, Dec 01, 2016 at 04:42:15PM -0800, Brian Norris wrote:
> Hi Dmitry,
> 
> On Thu, Dec 01, 2016 at 04:37:37PM -0800, Dmitry Torokhov wrote:
> > On Thu, Dec 01, 2016 at 04:31:10PM -0800, Brian Norris wrote:
> > > On some boards, we need to enable a regulator before using the HID, and
> > > it's also nice to save power in suspend by disabling it. Support an
> > > optional "vdd-supply" and a companion initialization delay.
> > > 
> > > Signed-off-by: Brian Norris <briannorris@...omium.org>
> > > Signed-off-by: Caesar Wang <wxt@...k-chips.com>
> > > Cc: Jiri Kosina <jikos@...nel.org>
> > > Cc: linux-input@...r.kernel.org
> > > ---
> > > v2:
> > >  * support compatible property for wacom, with specific "vdd-supply" name
> > >  * support the 100ms delay needed for this digitizer
> > >  * target regulator support only at specific device
> > > 
> > > v3:
> > >  * drop Wacom specifics and allow this to be used generically
> > >  * add "init-delay-ms" property support
> > > 
> > >  drivers/hid/i2c-hid/i2c-hid.c | 48 ++++++++++++++++++++++++++++++++++++++++++-
> > >  include/linux/i2c/i2c-hid.h   |  6 ++++++
> > >  2 files changed, 53 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
> > > index b3ec4f2de875..4cb523133d13 100644
> > > --- a/drivers/hid/i2c-hid/i2c-hid.c
> > > +++ b/drivers/hid/i2c-hid/i2c-hid.c
> > > @@ -37,7 +37,9 @@
> > >  #include <linux/mutex.h>
> > >  #include <linux/acpi.h>
> > >  #include <linux/of.h>
> > > +#include <linux/of_device.h>
> > >  #include <linux/gpio/consumer.h>
> > > +#include <linux/regulator/consumer.h>
> > >  
> > >  #include <linux/i2c/i2c-hid.h>
> > >  
> > > @@ -937,6 +939,22 @@ static int i2c_hid_of_probe(struct i2c_client *client,
> > >  	}
> > >  	pdata->hid_descriptor_address = val;
> > >  
> > > +	ret = of_property_read_u32(dev->of_node, "init-delay-ms", &val);
> > > +	if (!ret)
> > > +		pdata->init_delay_ms = ret;
> > > +
> > > +	pdata->supply = devm_regulator_get_optional(dev, "vdd");
> > 
> > Make it devm_regulator_get(), it's cleaner (you'll get a dummy regulator
> > that you can enable/disbale and not check if it is null or not).
> > 
> > 	pdata->supply = devm_regulator_get_optional(dev, "vdd");
> > 	if (IS_ERR(pdata->supply)) {
> > 		ret = PTR_ERR(pdata->supply);
> > 		if (ret != -EPROBE_DEFER)
> > 			dev_err(...);
> > 		return ret;
> > 	}
> 
> I had it as devm_regulator_get() in v1, but at that time, I was faking
> the firmware init delay using a regulator property. Now that I want to
> delay in this driver after enabling the regulator, I'd like to know the
> difference between a dummy and a real regulator. There's no need to wait
> after messing with the dummy regulator.

If there is no regulator in ACPI/DT there would not be "init-delay-ms"
property either.

Thanks.

-- 
Dmitry