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

[Kishon Vijay Abraham I <kishon@ti.com>]

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?

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);
>
>