Re: [PATCH v3] phy: Renesas R-Car Gen2 PHY driver

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Hello.

On 04/23/2014 02:02 PM, Kishon Vijay Abraham I wrote:

>>>> This PHY, though formally being a part of Renesas USBHS controller, contains
>>>> the
>>>> UGCTRL2 register that controls multiplexing of the USB ports (Renesas calls
>>>> them
>>>> channels) to the different USB controllers: channel 0 can be connected to
>>>> either
>>>> PCI EHCI/OHCI or USBHS controllers, channel 2 can be connected to PCI EHCI/OHCI
>>>> or xHCI controllers.

>>>> This is a new driver for this USB PHY currently already supported under
>>>> drivers/
>>>> usb/phy/. The reason for writing the new driver was the requirement that the
>>>> multiplexing of USB channels to the controller be dynamic, depending on what
>>>> USB drivers are loaded,  rather than static as provided by the old driver.
>>>> The infrastructure provided by drivers/phy/phy-core.c seems to fit that purpose
>>>> ideally. The new driver only supports device tree probing for now.

>>>> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>

>> [...]

>>>> Index: linux-phy/drivers/phy/phy-rcar-gen2.c
>>>> ===================================================================
>>>> --- /dev/null
>>>> +++ linux-phy/drivers/phy/phy-rcar-gen2.c
>>>> @@ -0,0 +1,283 @@

>> [...]

>>>> +static int rcar_gen2_phy_probe(struct platform_device *pdev)
>>>> +{

>> [...]

>>>> +    drv->phys[0][0].select_mask  = USBHS_UGCTRL2_USB0SEL;
>>>> +    drv->phys[0][0].select_value = USBHS_UGCTRL2_USB0SEL_PCI;
>>>> +    drv->phys[0][1].select_mask  = USBHS_UGCTRL2_USB0SEL;
>>>> +    drv->phys[0][1].select_value = USBHS_UGCTRL2_USB0SEL_HS_USB;
>>>> +    drv->phys[2][0].select_mask  = USBHS_UGCTRL2_USB2SEL;
>>>> +    drv->phys[2][0].select_value = USBHS_UGCTRL2_USB2SEL_PCI;
>>>> +    drv->phys[2][1].select_mask  = USBHS_UGCTRL2_USB2SEL;
>>>> +    drv->phys[2][1].select_value = USBHS_UGCTRL2_USB2SEL_USB30;
>>>> +
>>>> +    for (i = 0; i < NUM_USB_CHANNELS; i++) {

>>> Instead of hard coding the number of channels,

>>     It's hard coded in the hardware. We can even decrease that number to 2 as

> right, that's why thought dt should have that information.

    So you want a dedicated property for that or you meant something else?

>> for the channel #1 we have nothing to do, regardless of whether it's present or
>> not...

>>> we can model the channels (PHYs) as sub-nodes of the main PHY

>>     Hm, I don't think such representation would be adequate: the channels
>> themselves do not usually correspond to any particular PHY, that's why I used
>> #phy-cells = <2>.

>>> in dt and use it to create individual PHYs.

>>     Well, we probably can... however, I fail to see any immediate gain from
>> it here...
>>     I have to ask why you've selected this particular driver for such DT
>> representation experiments, despite it not being the first one supporting
>> multiple PHYs?

> just that it didn't strike before.. but I think all multiple PHYs should be
> modelled this way.

    I've basically reimplemented the driver to parse the info from the 
subnodes and it's now became larger in size, not smaller. :-/ Overall, I'm not 
content with the changes, nor do I think such a change in the DT 
representation was a great idea...

> Thanks
> Kishon

WBR, Sergei