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

    On Tuesday 02 June 2015 03:07 AM, NeilBrown wrote:
    > 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 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?

    ABI can never be removed or modified later. So should be really careful before
    adding it.

    Thanks
    Kishon

    >
    > 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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