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Message-ID: <556DB481.3080906@ti.com>
Date: Tue, 2 Jun 2015 19:19:53 +0530
From: Kishon Vijay Abraham I <kishon@...com>
To: NeilBrown <neilb@...e.de>
CC: NeilBrown <neil@...wn.name>, <linux-kernel@...r.kernel.org>,
GTA04 owners <gta04-owner@...delico.com>,
Tony Lindgren <tony@...mide.com>, Pavel Machek <pavel@....cz>,
<linux-omap@...r.kernel.org>
Subject: Re: [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@...com>
> wrote:
>
>> Hi,
>>
>> On Thursday 16 April 2015 01:33 PM, NeilBrown wrote:
>>> From: NeilBrown <neilb@...e.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@....cz>
>>> Signed-off-by: NeilBrown <neilb@...e.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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