Re: [Gta04-owner] [PATCH 5/6] phy: twl4030-usb: add support for reading resistor on ID pin.

["Dr. H. Nikolaus Schaller" <hns@goldelico.com>]

Hi Neil,

Am 01.06.2015 um 23:37 schrieb NeilBrown <neilb@suse.de>:

> On Mon, 1 Jun 2015 19:06:52 +0530 Kishon Vijay Abraham I <kishon@ti.com>
> wrote:
> 
>> Hi,
>> 
>> On Thursday 16 April 2015 01:33 PM, NeilBrown wrote:
>>> From: NeilBrown <neilb@suse.de>
>>> 
>>> The twl4030 phy can measure, with low precision, the
>>> resistance-to-ground of the ID pin.
>>> 
>>> Add a function to read the value, and export the result
>>> via sysfs.
>> 
>> Little sceptical about adding new sysfs entries. Do you have a good reason to 
>> add this?
> 
> The hardware can report the value, so why not present it to user-space?

I just had another idea how to present the value to user space.

The TWL6030 has connected the USB ID pin to one of the GPADC channels:

	http://lxr.free-electrons.com/source/drivers/iio/adc/twl6030-gpadc.c#L235

And therefore automatically presents the ID pin voltage through iio.

Would it be possible and useful to provide an iio interface for the resistance-to-ground
of the tw4030 ID pin as well?

This would resemble a 6 or 7 level ADC with non-linear scale, but better than nothing.

And to avoid the “floating” issue, it could also present some voltage value (assuming
a defined current).

So that “floating” is reported as some maximum voltage (e.g. 3.3V) and “ground” as 0V.

What do you think?

BR,
Nikolaus

> 
> I originally used this with a udev rule which would configure the maximum
> current based on the resistance measure - to work with the particular charger
> hardware I have.
> 
> More recent patches try to do all of the max-current configuration in the
> kernel, so I could live without exporting the value via sysfs if that is a
> show-stopper.
> 
> I can't see where the scepticism comes from though.  It is a well defined
> and cleary documented feature of the hardware.  Why not expose it?
> 
> Thanks,
> NeilBrown
> 
> 
>> 
>> Thanks
>> Kishon
>>> 
>>> If the read fails, which it does sometimes, try again in 50msec.
>>> 
>>> Acked-by: Pavel Machek <pavel@ucw.cz>
>>> Signed-off-by: NeilBrown <neilb@suse.de>
>>> ---
>>>  .../ABI/testing/sysfs-platform-twl4030-usb         |   22 +++++++
>>>  drivers/phy/phy-twl4030-usb.c                      |   63 ++++++++++++++++++++
>>>  2 files changed, 85 insertions(+)
>>> 
>>> diff --git a/Documentation/ABI/testing/sysfs-platform-twl4030-usb b/Documentation/ABI/testing/sysfs-platform-twl4030-usb
>>> index 512c51be64ae..425d23676f8a 100644
>>> --- a/Documentation/ABI/testing/sysfs-platform-twl4030-usb
>>> +++ b/Documentation/ABI/testing/sysfs-platform-twl4030-usb
>>> @@ -6,3 +6,25 @@ Description:
>>>  	Possible values: "on", "off".
>>> 
>>>  	Changes are notified via select/poll.
>>> +
>>> +What: /sys/bus/platform/devices/*twl4030-usb/id
>>> +Description:
>>> +	Read-only report on measurement of USB-OTG ID pin.
>>> +
>>> +	The ID pin may be floating, grounded, or pulled to
>>> +	ground by a resistor.
>>> +
>>> +	A very course grained reading of the resistance is
>>> +	available.  The numbers given in kilo-ohms are roughly
>>> +	the center-point of the detected range.
>>> +
>>> +	Possible values are:
>>> +		ground
>>> +		102k
>>> +		200k
>>> +		440k
>>> +		floating
>>> +		unknown
>>> +
>>> +	"unknown" indicates a problem with trying to detect
>>> +	the resistance.
>>> diff --git a/drivers/phy/phy-twl4030-usb.c b/drivers/phy/phy-twl4030-usb.c
>>> index 3a707dd14238..1d6f3e70193e 100644
>>> --- a/drivers/phy/phy-twl4030-usb.c
>>> +++ b/drivers/phy/phy-twl4030-usb.c
>>> @@ -379,6 +379,56 @@ static void twl4030_i2c_access(struct twl4030_usb *twl, int on)
>>>  	}
>>>  }
>>> 
>>> +enum twl4030_id_status {
>>> +	TWL4030_GROUND,
>>> +	TWL4030_102K,
>>> +	TWL4030_200K,
>>> +	TWL4030_440K,
>>> +	TWL4030_FLOATING,
>>> +	TWL4030_ID_UNKNOWN,
>>> +};
>>> +static char *twl4030_id_names[] = {
>>> +	"ground",
>>> +	"102k",
>>> +	"200k",
>>> +	"440k",
>>> +	"floating",
>>> +	"unknown"
>>> +};
>>> +
>>> +enum twl4030_id_status twl4030_get_id(struct twl4030_usb *twl)
>>> +{
>>> +	int ret;
>>> +
>>> +	pm_runtime_get_sync(twl->dev);
>>> +	if (twl->usb_mode == T2_USB_MODE_ULPI)
>>> +		twl4030_i2c_access(twl, 1);
>>> +	ret = twl4030_usb_read(twl, ULPI_OTG_CTRL);
>>> +	if (ret < 0 || !(ret & ULPI_OTG_ID_PULLUP)) {
>>> +		/* Need pull-up to read ID */
>>> +		twl4030_usb_set_bits(twl, ULPI_OTG_CTRL,
>>> +				     ULPI_OTG_ID_PULLUP);
>>> +		mdelay(50);
>>> +	}
>>> +	ret = twl4030_usb_read(twl, ID_STATUS);
>>> +	if (ret < 0 || (ret & 0x1f) == 0) {
>>> +		mdelay(50);
>>> +		ret = twl4030_usb_read(twl, ID_STATUS);
>>> +	}
>>> +
>>> +	if (twl->usb_mode == T2_USB_MODE_ULPI)
>>> +		twl4030_i2c_access(twl, 0);
>>> +	pm_runtime_put_autosuspend(twl->dev);
>>> +
>>> +	if (ret < 0)
>>> +		return TWL4030_ID_UNKNOWN;
>>> +	ret = ffs(ret) - 1;
>>> +	if (ret < TWL4030_GROUND || ret > TWL4030_FLOATING)
>>> +		return TWL4030_ID_UNKNOWN;
>>> +
>>> +	return ret;
>>> +}
>>> +
>>>  static void __twl4030_phy_power(struct twl4030_usb *twl, int on)
>>>  {
>>>  	u8 pwr = twl4030_usb_read(twl, PHY_PWR_CTRL);
>>> @@ -532,6 +582,16 @@ static ssize_t twl4030_usb_vbus_show(struct device *dev,
>>>  }
>>>  static DEVICE_ATTR(vbus, 0444, twl4030_usb_vbus_show, NULL);
>>> 
>>> +static ssize_t twl4030_usb_id_show(struct device *dev,
>>> +				   struct device_attribute *attr,
>>> +				   char *buf)
>>> +{
>>> +	struct twl4030_usb *twl = dev_get_drvdata(dev);
>>> +	return scnprintf(buf, PAGE_SIZE, "%s\n",
>>> +			 twl4030_id_names[twl4030_get_id(twl)]);
>>> +}
>>> +static DEVICE_ATTR(id, 0444, twl4030_usb_id_show, NULL);
>>> +
>>>  static irqreturn_t twl4030_usb_irq(int irq, void *_twl)
>>>  {
>>>  	struct twl4030_usb *twl = _twl;
>>> @@ -709,6 +769,8 @@ static int twl4030_usb_probe(struct platform_device *pdev)
>>>  	platform_set_drvdata(pdev, twl);
>>>  	if (device_create_file(&pdev->dev, &dev_attr_vbus))
>>>  		dev_warn(&pdev->dev, "could not create sysfs file\n");
>>> +	if (device_create_file(&pdev->dev, &dev_attr_id))
>>> +		dev_warn(&pdev->dev, "could not create sysfs file\n");
>>> 
>>>  	ATOMIC_INIT_NOTIFIER_HEAD(&twl->phy.notifier);
>>> 
>>> @@ -753,6 +815,7 @@ static int twl4030_usb_remove(struct platform_device *pdev)
>>>  	pm_runtime_get_sync(twl->dev);
>>>  	cancel_delayed_work(&twl->id_workaround_work);
>>>  	device_remove_file(twl->dev, &dev_attr_vbus);
>>> +	device_remove_file(twl->dev, &dev_attr_id);
>>> 
>>>  	/* set transceiver mode to power on defaults */
>>>  	twl4030_usb_set_mode(twl, -1);
>>> 
>>> 
> 
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