[PATCH v3 1/2] devicetree: i2c-hid: Add regulator support

[PATCH v3 1/2] devicetree: i2c-hid: Add regulator support

[Brian Norris]

From: Caesar Wang <wxt-TNX95d0MmH7DzftRWevZcw@public.gmane.org>

Document a "vdd-supply" and an initialization delay. Can be used for
powering on/off a HID.

Signed-off-by: Caesar Wang <wxt-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
Cc: Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Jiri Kosina <jikos-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: linux-input-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Signed-off-by: Brian Norris <briannorris-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
---
v2:
 * add compatible property for wacom, per Rob's request
 * name the regulator property specifically (VDD)

v3:
 * remove wacom property, per Benjamin's request
 * add delay property

 Documentation/devicetree/bindings/input/hid-over-i2c.txt | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/hid-over-i2c.txt b/Documentation/devicetree/bindings/input/hid-over-i2c.txt
index 488edcb264c4..1ea290167652 100644
--- a/Documentation/devicetree/bindings/input/hid-over-i2c.txt
+++ b/Documentation/devicetree/bindings/input/hid-over-i2c.txt
@@ -17,6 +17,11 @@ Required properties:
 - interrupt-parent: the phandle for the interrupt controller
 - interrupts: interrupt line
 
+Optional properties:
+- vdd-supply: phandle of the regulator that provides the supply voltage.
+- init-delay-ms: time required by the device after power-on before it is ready
+  for communication.
+
 Example:
 
 	i2c-hid-dev@2c {
-- 
2.8.0.rc3.226.g39d4020

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

[Brian Norris]

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@chromium.org>
Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: linux-input@vger.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");
+	if (IS_ERR(pdata->supply)) {
+		ret = PTR_ERR(pdata->supply);
+		pdata->supply = NULL;
+		if (ret == -EPROBE_DEFER)
+			return ret;
+		if (ret == -ENODEV)
+			return 0;
+		dev_err(dev, "Failed to get regulator: %d\n", ret);
+		return ret;
+	}
+
 	return 0;
 }
 
@@ -983,6 +1001,17 @@ static int i2c_hid_probe(struct i2c_client *client,
 		ihid->pdata = *platform_data;
 	}
 
+	if (ihid->pdata.supply) {
+		ret = regulator_enable(ihid->pdata.supply);
+		if (ret < 0) {
+			dev_err(&client->dev, "Failed to enable regulator: %d\n",
+				ret);
+			return ret;
+		}
+		if (ihid->pdata.init_delay_ms)
+			msleep(ihid->pdata.init_delay_ms);
+	}
+
 	if (client->irq > 0) {
 		ihid->irq = client->irq;
 	} else if (ACPI_COMPANION(&client->dev)) {
@@ -1100,6 +1129,9 @@ static int i2c_hid_remove(struct i2c_client *client)
 	if (ihid->desc)
 		gpiod_put(ihid->desc);
 
+	if (ihid->pdata.supply)
+		regulator_disable(ihid->pdata.supply);
+
 	kfree(ihid);
 
 	acpi_dev_remove_driver_gpios(ACPI_COMPANION(&client->dev));
@@ -1152,6 +1184,11 @@ static int i2c_hid_suspend(struct device *dev)
 		else
 			hid_warn(hid, "Failed to enable irq wake: %d\n",
 				wake_status);
+	} else if (ihid->pdata.supply) {
+		ret = regulator_disable(ihid->pdata.supply);
+		if (ret < 0)
+			hid_warn(hid, "Failed to disable supply: %d\n",
+				 ret);
 	}
 
 	return 0;
@@ -1165,7 +1202,16 @@ static int i2c_hid_resume(struct device *dev)
 	struct hid_device *hid = ihid->hid;
 	int wake_status;
 
-	if (device_may_wakeup(&client->dev) && ihid->irq_wake_enabled) {
+	if (!device_may_wakeup(&client->dev)) {
+		if (ihid->pdata.supply) {
+			ret = regulator_enable(ihid->pdata.supply);
+			if (ret < 0)
+				hid_warn(hid, "Failed to enable supply: %d\n",
+					 ret);
+			if (ihid->pdata.init_delay_ms)
+				msleep(ihid->pdata.init_delay_ms);
+		}
+	} else if (ihid->irq_wake_enabled) {
 		wake_status = disable_irq_wake(ihid->irq);
 		if (!wake_status)
 			ihid->irq_wake_enabled = false;
diff --git a/include/linux/i2c/i2c-hid.h b/include/linux/i2c/i2c-hid.h
index 7aa901d92058..97688cde4a91 100644
--- a/include/linux/i2c/i2c-hid.h
+++ b/include/linux/i2c/i2c-hid.h
@@ -14,9 +14,13 @@
 
 #include <linux/types.h>
 
+struct regulator;
+
 /**
  * struct i2chid_platform_data - used by hid over i2c implementation.
  * @hid_descriptor_address: i2c register where the HID descriptor is stored.
+ * @supply: regulator for powering on the device.
+ * @init_delay_ms: delay after powering on before device is usable.
  *
  * Note that it is the responsibility of the platform driver (or the acpi 5.0
  * driver, or the flattened device tree) to setup the irq related to the gpio in
@@ -31,6 +35,8 @@
  */
 struct i2c_hid_platform_data {
 	u16 hid_descriptor_address;
+	struct regulator *supply;
+	int init_delay_ms;
 };
 
 #endif /* __LINUX_I2C_HID_H */
-- 
2.8.0.rc3.226.g39d4020

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

[Dmitry Torokhov]

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@chromium.org>
> Signed-off-by: Caesar Wang <wxt@rock-chips.com>
> Cc: Jiri Kosina <jikos@kernel.org>
> Cc: linux-input@vger.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;
	}

Thanks.

> +	if (IS_ERR(pdata->supply)) {
> +		ret = PTR_ERR(pdata->supply);
> +		pdata->supply = NULL;
> +		if (ret == -EPROBE_DEFER)
> +			return ret;
> +		if (ret == -ENODEV)
> +			return 0;
> +		dev_err(dev, "Failed to get regulator: %d\n", ret);
> +		return ret;
> +	}
> +
>  	return 0;
>  }
>  
> @@ -983,6 +1001,17 @@ static int i2c_hid_probe(struct i2c_client *client,
>  		ihid->pdata = *platform_data;
>  	}
>  
> +	if (ihid->pdata.supply) {
> +		ret = regulator_enable(ihid->pdata.supply);
> +		if (ret < 0) {
> +			dev_err(&client->dev, "Failed to enable regulator: %d\n",
> +				ret);
> +			return ret;
> +		}
> +		if (ihid->pdata.init_delay_ms)
> +			msleep(ihid->pdata.init_delay_ms);
> +	}
> +
>  	if (client->irq > 0) {
>  		ihid->irq = client->irq;
>  	} else if (ACPI_COMPANION(&client->dev)) {
> @@ -1100,6 +1129,9 @@ static int i2c_hid_remove(struct i2c_client *client)
>  	if (ihid->desc)
>  		gpiod_put(ihid->desc);
>  
> +	if (ihid->pdata.supply)
> +		regulator_disable(ihid->pdata.supply);
> +
>  	kfree(ihid);
>  
>  	acpi_dev_remove_driver_gpios(ACPI_COMPANION(&client->dev));
> @@ -1152,6 +1184,11 @@ static int i2c_hid_suspend(struct device *dev)
>  		else
>  			hid_warn(hid, "Failed to enable irq wake: %d\n",
>  				wake_status);
> +	} else if (ihid->pdata.supply) {
> +		ret = regulator_disable(ihid->pdata.supply);
> +		if (ret < 0)
> +			hid_warn(hid, "Failed to disable supply: %d\n",
> +				 ret);
>  	}
>  
>  	return 0;
> @@ -1165,7 +1202,16 @@ static int i2c_hid_resume(struct device *dev)
>  	struct hid_device *hid = ihid->hid;
>  	int wake_status;
>  
> -	if (device_may_wakeup(&client->dev) && ihid->irq_wake_enabled) {
> +	if (!device_may_wakeup(&client->dev)) {
> +		if (ihid->pdata.supply) {
> +			ret = regulator_enable(ihid->pdata.supply);
> +			if (ret < 0)
> +				hid_warn(hid, "Failed to enable supply: %d\n",
> +					 ret);
> +			if (ihid->pdata.init_delay_ms)
> +				msleep(ihid->pdata.init_delay_ms);
> +		}
> +	} else if (ihid->irq_wake_enabled) {
>  		wake_status = disable_irq_wake(ihid->irq);
>  		if (!wake_status)
>  			ihid->irq_wake_enabled = false;
> diff --git a/include/linux/i2c/i2c-hid.h b/include/linux/i2c/i2c-hid.h
> index 7aa901d92058..97688cde4a91 100644
> --- a/include/linux/i2c/i2c-hid.h
> +++ b/include/linux/i2c/i2c-hid.h
> @@ -14,9 +14,13 @@
>  
>  #include <linux/types.h>
>  
> +struct regulator;
> +
>  /**
>   * struct i2chid_platform_data - used by hid over i2c implementation.
>   * @hid_descriptor_address: i2c register where the HID descriptor is stored.
> + * @supply: regulator for powering on the device.
> + * @init_delay_ms: delay after powering on before device is usable.
>   *
>   * Note that it is the responsibility of the platform driver (or the acpi 5.0
>   * driver, or the flattened device tree) to setup the irq related to the gpio in
> @@ -31,6 +35,8 @@
>   */
>  struct i2c_hid_platform_data {
>  	u16 hid_descriptor_address;
> +	struct regulator *supply;
> +	int init_delay_ms;
>  };
>  
>  #endif /* __LINUX_I2C_HID_H */
> -- 
> 2.8.0.rc3.226.g39d4020
> 

-- 
Dmitry

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

[Brian Norris]

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@chromium.org>
> > Signed-off-by: Caesar Wang <wxt@rock-chips.com>
> > Cc: Jiri Kosina <jikos@kernel.org>
> > Cc: linux-input@vger.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.

Brian

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

[Dmitry Torokhov]

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-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> > > Signed-off-by: Caesar Wang <wxt-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
> > > Cc: Jiri Kosina <jikos-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> > > Cc: linux-input-u79uwXL29TY76Z2rM5mHXA@public.gmane.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
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Re: [PATCH v3 2/2] HID: i2c-hid: support regulator power on/off

[Brian Norris]

On Thu, Dec 01, 2016 at 05:16:15PM -0800, Dmitry Torokhov wrote:
> On Thu, Dec 01, 2016 at 04:42:15PM -0800, Brian Norris wrote:
> > 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-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> > > > Signed-off-by: Caesar Wang <wxt-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
> > > > Cc: Jiri Kosina <jikos-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> > > > Cc: linux-input-u79uwXL29TY76Z2rM5mHXA@public.gmane.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

...

> > > > @@ -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.

I suppose that's a fair assumption... the difference being that you
assumed it, and I enforced it :)

Anyway, I can respin without the _optional(). I'll wait at least a day
or so, as the DT binding could use some review (it's the more
controversial piece).

Brian