[PATCH] usb: dwc3-meson-g12a: add power-on/off of the PHYs

[Marek Vasut]

On 4/20/20 4:47 PM, Neil Armstrong wrote:
> On 20/04/2020 16:10, Marek Vasut wrote:
>> On 4/20/20 4:07 PM, Neil Armstrong wrote:
>> [...]
>>
>>>>>>>> Doesn't checkpatch complain about this extra space before semicolon ?
>>>>>>>
>>>>>>> Nop, even in --strict
>>>>>>
>>>>>> Shouldn't it though ? I thought this extra space was forbidden.
>>>>>
>>>>> No idea, this line is copied from the for loop doing the phy init,
>>>>> itself copied from the Linux code passing all checkpatch checks.
>>>>
>>>> Could you change it to for (i = 0; i < PHY_COUNT; i++) please ?
>>>
>>> Sure
>>
>> Thank you.
>>
>> ( I'm still surprised checkpatch doesn't warn about it, I was quite sure
>> it was one of the checks at some point, hmmmmm. )
>>
>>>>>>>>
>>>>>>>>> +		if (!priv->phys[i].dev)
>>>>>>>>> +			continue;
>>>>>>>>> +
>>>>>>>>> +		ret = generic_phy_power_on(&priv->phys[i]);
>>>>>>>>
>>>>>>>> Do we really need to turn on all the PHYs ?
>>>>>>>>
>>>>>>>
>>>>>>> Yes
>>>>>>
>>>>>> Then should we have something like clk_bulk_*(), but for phys ?
>>>>>>
>>>>>
>>>>> Eventually, yes, but this goes beyond a fix.
>>>>
>>>> The merge window is open for quite a bit longer, so doing this in a
>>>> generic way would be appreciated.
>>>>
>>>> btw while you're at it, shouldn't the PHY_COUNT be replaced with some
>>>> PHY count detection by reading the DT ? ( I don't have the hardware and
>>>> I don't know the amlogic SoCs though )
>>>>
>>>
>>> Hmm, the PHYs list can have some holes (i.e only the second PHY could be used on 3),
>>> and the name of the PHY determines it's type and position (PHY1 is a special OTG phy)
>>> this is why we loop over a fixed array and check if the PHY pointer exists.
>>
>> Um, that sounds like a vaguely familiar problem. Is that an issue with
>> mapping between controller and a USB PHY ? Is that mapping fixed or is
>> it configured from DT ? 
> 
> Mapping is done via DT, all PHYs are optional depending on the board layout.
> 
>> And then, should all PHYs really be powered on,
>> or should only the PHY matching the currently used controller be powered
>> on ?
> 
> All PHYs are connected to a glue that muxes 1 PHY between DWC2 and DWC3, and
> the other USB2 PHYs (for now 1, but previous SoCs had 2) to DWC3, the USB3 PHY
> is muxed between PCIe to dw-pcie and DWC3.
> 
> So we power-on only the PHYs specified in DT, thus the:
> 	if (!priv->phys[i].dev)
> 		continue;
> 
> I attached the USB complex diagram if you need it.

OK, thanks for clarifying. Now, can you document this in the commit
message, so we have this information stored somewhere for future
reference ? This would be real useful.