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Re: [PATCH v2 1/5] phy: Add a driver for simple phy

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  Re: [PATCH v2 1/5] phy: Add a driver for simple phy Arnd Bergmann <arnd@arndb.de> - 2016-04-16 22:00 +0200
    Re: [PATCH v2 1/5] phy: Add a driver for simple phy Kishon Vijay Abraham I <kishon@ti.com> - 2016-04-18 14:40 +0200
      Re: [PATCH v2 1/5] phy: Add a driver for simple phy Arnd Bergmann <arnd@arndb.de> - 2016-04-18 16:50 +0200

#1380605 — Re: [PATCH v2 1/5] phy: Add a driver for simple phy

On Thursday 14 April 2016 11:22:58 Kishon Vijay Abraham I wrote:
> 
> IMO simple-phy driver should be an independent driver and shouldn't export
> symbols. The dt binding for the simple phy device should be something like
> below where all the properties of the simple phy device should be in the
> binding documentation.
> usbphy {
>         compatible = "simple-phy";
>         phy-supply = <&supply>;
>         clocks = <&clock>;
>         reset = <&reset>;
> };
> 
> Anything that needs more than this shouldn't be a simple phy.

I think there are two aspects here:

a) I agree that a driver that matches "simple-phy" should only call
   the generic functions and not use any other properties.

b) Independent of that, I think that it makes a lot of sense to export
   those functions from the generic PHY subsystems so they can be
   called from drivers that are a little less generic, or that already
   have an established binding but need no other code.

	Arnd

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#1381663

Hi Arnd,

On Sunday 17 April 2016 01:20 AM, Arnd Bergmann wrote:
> On Thursday 14 April 2016 11:22:58 Kishon Vijay Abraham I wrote:
>>
>> IMO simple-phy driver should be an independent driver and shouldn't export
>> symbols. The dt binding for the simple phy device should be something like
>> below where all the properties of the simple phy device should be in the
>> binding documentation.
>> usbphy {
>>         compatible = "simple-phy";
>>         phy-supply = <&supply>;
>>         clocks = <&clock>;
>>         reset = <&reset>;
>> };
>>
>> Anything that needs more than this shouldn't be a simple phy.
> 
> I think there are two aspects here:
> 
> a) I agree that a driver that matches "simple-phy" should only call
>    the generic functions and not use any other properties.
> 
> b) Independent of that, I think that it makes a lot of sense to export
>    those functions from the generic PHY subsystems so they can be
>    called from drivers that are a little less generic, or that already
>    have an established binding but need no other code.

These export functions can be abused and called directly from the controller
driver bypassing the phy core.

Actually lot of generic PHY programming are done in the phy-core itself. (For
example, the generic PHY regulator binding "phy-supply" can be used for the phy
core to enable the regulator during power on and disable during power off, phy
core also invokes pm_runtime API's during power_on and power_off which can be
used to enable/disable clocks). So drivers which are less generic can just
populate their specific handling part in their phy ops and leave the rest to be
done in phy core.
"simple-phy" should be used to avoid adding new PHY drivers that does simple
PHY ops.

Thanks
Kishon

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#1381774

On Monday 18 April 2016 18:00:19 Kishon Vijay Abraham I wrote:
> Hi Arnd,
> 
> On Sunday 17 April 2016 01:20 AM, Arnd Bergmann wrote:
> > On Thursday 14 April 2016 11:22:58 Kishon Vijay Abraham I wrote:
> >>
> >> IMO simple-phy driver should be an independent driver and shouldn't export
> >> symbols. The dt binding for the simple phy device should be something like
> >> below where all the properties of the simple phy device should be in the
> >> binding documentation.
> >> usbphy {
> >>         compatible = "simple-phy";
> >>         phy-supply = <&supply>;
> >>         clocks = <&clock>;
> >>         reset = <&reset>;
> >> };
> >>
> >> Anything that needs more than this shouldn't be a simple phy.
> > 
> > I think there are two aspects here:
> > 
> > a) I agree that a driver that matches "simple-phy" should only call
> >    the generic functions and not use any other properties.
> > 
> > b) Independent of that, I think that it makes a lot of sense to export
> >    those functions from the generic PHY subsystems so they can be
> >    called from drivers that are a little less generic, or that already
> >    have an established binding but need no other code.
> 
> These export functions can be abused and called directly from the controller
> driver bypassing the phy core.
> 
> Actually lot of generic PHY programming are done in the phy-core itself. (For
> example, the generic PHY regulator binding "phy-supply" can be used for the phy
> core to enable the regulator during power on and disable during power off, phy
> core also invokes pm_runtime API's during power_on and power_off which can be
> used to enable/disable clocks). So drivers which are less generic can just
> populate their specific handling part in their phy ops and leave the rest to be
> done in phy core.
> "simple-phy" should be used to avoid adding new PHY drivers that does simple
> PHY ops.

Having the phy core do everything automatically indeed sounds superior here,
the simple-phy driver can then become a trivial stub without any calls
into the regulator/clk/reset subsystems. If that works (or can be made to
work), that's great.

	Arnd

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