Re: [PATCH v4 3/7] phy: Add set_mode callback

[David Lechner <david@lechnology.com>]

On 05/04/2016 01:10 PM, Bin Liu wrote:
> Hi,
>
> On Thu, Apr 14, 2016 at 01:35:14PM -0500, David Lechner wrote:
>> The initial use for this is for PHYs that have a mode related to USB OTG.
>> There are several SoCs (e.g. TI OMAP and DA8xx) that have a mode setting
>> in the USB PHY to override OTG VBUS and ID signals.
>>
>> Of course, the enum can be expaned in the future to include modes for
>> other types of PHYs as well.
>>
>> Suggested-by: Kishon Vijay Abraham I <kishon@ti.com>
>> Signed-off-by: David Lechner <david@lechnology.com>
>> ---
>>
>> v4 changes:
>>
>> * This is a new patch to avoid exporting a symbol from the phy-da8xx-usb driver.
>>
>>
>>   drivers/phy/phy-core.c  | 15 +++++++++++++++
>>   include/linux/phy/phy.h | 15 +++++++++++++++
>>   2 files changed, 30 insertions(+)
>>
>> diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
>> index e7e574d..fe0344c 100644
>> --- a/drivers/phy/phy-core.c
>> +++ b/drivers/phy/phy-core.c
>> @@ -342,6 +342,21 @@ int phy_power_off(struct phy *phy)
>>   }
>>   EXPORT_SYMBOL_GPL(phy_power_off);
>>
>> +int phy_set_mode(struct phy *phy, enum phy_mode mode)
>> +{
>> +	int ret;
>> +
>> +	if (!phy || !phy->ops->set_mode)
>> +		return 0;
>> +
>> +	mutex_lock(&phy->mutex);
>> +	ret = phy->ops->set_mode(phy, mode);
>> +	mutex_unlock(&phy->mutex);
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(phy_set_mode);
>
> Sorry for my late comments, have been busy on other things.
>
> As I commented in v2, isn't it a better idea to not adding this callback
> and let the da8xx phy driver set the mode register in _probe() based on
> DT dr_mode?
>
> musb core only calls the *optional* _set_mode() during init, so I don't
> see any problem if the phy set the mode in its probe.
>
> Regards,
> -Bin.
>

As was already discussed, the mode can be changed via sysfs as well as 
during probe, so this callback is needed for that case.

This is something I actually plan on using because the device I am using 
(LEGO MINDSTORMS EV3) is not wired for OTG, so the callback is needed to 
override the ID and VBUS signals when switching between host and 
peripheral mode.