linux-kernel - Re: [PATCH 08/18] staging: typec: fusb302: Add support for USB2 charger detection through extcon

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Date:   Sun, 6 Aug 2017 07:58:57 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Hans de Goede <hdegoede@...hat.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Sebastian Reichel <sre@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org, Liam Breck <liam@...workimprov.net>,
        Tony Lindgren <tony@...mide.com>, linux-pm@...r.kernel.org,
        devel@...verdev.osuosl.org
Subject: Re: [PATCH 08/18] staging: typec: fusb302: Add support for USB2
 charger detection through extcon

On 08/06/2017 07:36 AM, Hans de Goede wrote:
> Hi,
> 
> On 06-08-17 16:22, Guenter Roeck wrote:
>> On 08/06/2017 05:35 AM, Hans de Goede wrote:
>>> The fusb302 port-controller relies on an external device doing USB2
>>> charger-type detection.
>>>
>>> The Intel Whiskey Cove PMIC with which the fusb302 is combined on some
>>> X86/ACPI platforms already has a charger-type detection driver which
>>> uses extcon to communicate the detected charger-type.
>>>
>>> This commit uses the tcpm_get_usb2_current_limit_extcon helper to enable
>>> USB2 charger detection on these systems. Note that the "fcs,extcon-name"
>>> property name is only for kernel internal use by X86/ACPI platform code
>>> and as such is NOT documented in the devicetree bindings.
>>>
>>> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
>>> ---
>>>   drivers/staging/typec/fusb302/fusb302.c | 16 ++++++++++++++++
>>>   1 file changed, 16 insertions(+)
>>>
>>> diff --git a/drivers/staging/typec/fusb302/fusb302.c b/drivers/staging/typec/fusb302/fusb302.c
>>> index be454b5ff6c7..1d8c9b66df2f 100644
>>> --- a/drivers/staging/typec/fusb302/fusb302.c
>>> +++ b/drivers/staging/typec/fusb302/fusb302.c
>>> @@ -1201,6 +1201,8 @@ static void init_tcpc_dev(struct tcpc_dev *fusb302_tcpc_dev)
>>>   {
>>>       fusb302_tcpc_dev->init = tcpm_init;
>>>       fusb302_tcpc_dev->get_vbus = tcpm_get_vbus;
>>> +    fusb302_tcpc_dev->get_usb2_current_limit =
>>> +        tcpm_get_usb2_current_limit_extcon;
>>>       fusb302_tcpc_dev->set_cc = tcpm_set_cc;
>>>       fusb302_tcpc_dev->get_cc = tcpm_get_cc;
>>>       fusb302_tcpc_dev->set_polarity = tcpm_set_polarity;
>>> @@ -1685,6 +1687,7 @@ static int fusb302_probe(struct i2c_client *client,
>>>       struct fusb302_chip *chip;
>>>       struct i2c_adapter *adapter;
>>>       struct device *dev = &client->dev;
>>> +    const char *name;
>>>       int ret = 0;
>>>       u32 val;
>>> @@ -1717,6 +1720,19 @@ static int fusb302_probe(struct i2c_client *client,
>>>       if (device_property_read_u32(dev, "fcs,operating-snk-mw", &val) == 0)
>>>           chip->tcpc_config.operating_snk_mw = val;
>>> +    /*
>>> +     * Devicetree platforms should get extcon via phandle (not yet
>>> +     * supported). On ACPI platforms, we get the name from a device prop.
>>> +     * This device prop is for kernel internal use only and is expected
>>> +     * to be set by the platform code which also registers the i2c client
>>> +     * for the fusb302.
>>> +     */
>>> +    if (device_property_read_string(dev, "fcs,extcon-name", &name) == 0) {
>>
>> Those new devicetree properties need to be documented and approved by dt maintainers.
> 
> As indicated by the comment, this property should not be used in the devicetree
> case, notice this is a device-property and not an of property and since it is
> not intended to be used with devicetree at all (in devicetree a phandle rather
> then a name would be used), it has no place under Documentation/devicetree at all.
> 

Ok. I thought device properties were supposed to unify dt and non-dt situations,
but apparently not. Oh well :-(.

> Also there is no current binding documentation for the "fcs,fusb302" compatible
> and the weird "fcs,int_n" gpio which really is an irq which it already uses.
> 

Yes, one of those TODO items for moving the code out of staging. "fcs," should
possibly be "fusb302,", and int_n _is_ weird.

> 
>>
>>> +        chip->tcpc_dev.usb2_extcon = extcon_get_extcon_dev(name);
>>> +        if (!chip->tcpc_dev.usb2_extcon)
>>
>> extcon_get_extcon_dev() can also return an ERR_PTR.
>>
>> As before, I am not really happy typing this into tcpm via tcpc_dev.
>> Until we have a better solution, I would prefer for that code to stay with the fusb302
>> code.
> 
> Ok, I tried to make this all re-usable since I think other port-controller drivers
> will need something similar, but I can kill the entire tcpm-helpers.c file in v2
> and then put everything in fusb302.c. I take it that that is what you want ?
> 
Yes, please.

Also, please copy Yueyao Zhu for the fusb302 changes in v2.

Thanks,
Guenter