Re: [PATCH v2 0/2] usb: dwc2: Use clk bulk API for supporting multiple clocks

[Sascha Hauer <s.hauer@pengutronix.de>]

On Tue, Feb 09, 2021 at 10:54:24AM -0600, Rob Herring wrote:
> On Mon, Jan 25, 2021 at 10:38:23AM +0100, Sascha Hauer wrote:
> > Currently the dwc2 driver only supports a single clock. I have a board
> > here which has a dwc2 controller with a somewhat special clock routing
> > to the phy. Both the dwc2 controller and the ULPI phy get their phy
> > clock from a SI5351 clock generator. This clock generator has multiple
> > clock outputs which each is modelled as a separate clk in Linux.
> > Unfortunately the clock to the phy and the clock to the dwc2 core are on
> > two different output pins of the SI5351, so we have two clocks which
> > must be enabled.  The phy is driven by the usb-nop-xceiver driver which
> > supports a single clock. My first approach was to add support for a
> > second clock to that driver, but technically the other clock is
> > connected to the dwc2 core, so instead I added support for a second
> > clock to the dwc2 driver.  This can easily be archieved with the clk
> > bulk API as done in this series.
> 
> Where is the usb-nop-xceiver single clock coming from?

It's coming from the SI5351 clock generator

> 
> Maybe you shouldn't be using usb-nop-xceiver? There is a ULPI binding 
> though that alone doesn't really help you.

The clock that feeds the phy is handled by the usb-nop-xceiver just
fine, it's the clock that is fed to the DWC2 controller that I need
support for. I hope my other mail makes this clearer a bit.

Sascha

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