linux-kernel - RE: [PATCH/RFC] phy: renesas: rcar-gen3-usb2-clksel: Add R-Car Gen3 USB 2.0 clock selector PHY

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Date:   Mon, 26 Jun 2017 07:52:52 +0000
From:   Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
To:     Rob Herring <robh@...nel.org>
CC:     "kishon@...com" <kishon@...com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>
Subject: RE: [PATCH/RFC] phy: renesas: rcar-gen3-usb2-clksel: Add R-Car Gen3
 USB 2.0 clock selector PHY

Hi,

> -----Original Message-----
> From: Rob Herring
> Sent: Saturday, June 24, 2017 3:21 AM
> 
> On Thu, Jun 15, 2017 at 08:34:22PM +0900, Yoshihiro Shimoda wrote:
> > USB 2.0 PHY of R-Car Gen3 can change the clock source from an oscillator
> > to an external clock via a register. So, this patch adds support
> > the clock source selector as a generic PHY driver.
> >
> > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
> > ---
> >  This patch is based on the latest linux-phy.git / next branch
> >  (commit id = 787f24543c4a599e5d9d311a3fce839ce87bbff0)
> >
> >  I'm not sure this driver ss OK or not as a generic phy driver.
> >  So, I send this patch as RFC.
> >
> >  .../bindings/phy/rcar-gen3-phy-usb2-clksel.txt     |  58 +++++++++
> >  drivers/phy/renesas/Kconfig                        |   8 ++
> >  drivers/phy/renesas/Makefile                       |   1 +
> >  drivers/phy/renesas/phy-rcar-gen3-usb2-clksel.c    | 129 +++++++++++++++++++++
> >  4 files changed, 196 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/phy/rcar-gen3-phy-usb2-clksel.txt
> >  create mode 100644 drivers/phy/renesas/phy-rcar-gen3-usb2-clksel.c
> >
> > diff --git a/Documentation/devicetree/bindings/phy/rcar-gen3-phy-usb2-clksel.txt
> b/Documentation/devicetree/bindings/phy/rcar-gen3-phy-usb2-clksel.txt
> > new file mode 100644
> > index 0000000..71b2f1b
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/phy/rcar-gen3-phy-usb2-clksel.txt
> > @@ -0,0 +1,58 @@
> > +* Renesas R-Car generation 3 USB 2.0 clock selector PHY
> > +
> > +This file provides information on what the device node for the R-Car generation
> > +3 USB 2.0 clock selector PHY contains.
> 
> Is this a phy or just a clock selector and nothing else? It sounds more
> like the latter and you should use the clock binding. Whether this is a
> phy driver in the kernel is a separate question really.

Thank you for the comment. This is just a clock selector.
So, I will try to make a clock driver for this.

Best regards,
Yoshihiro Shimoda

> > +
> > +If you connect an external clock to the USB_EXTAL pin, you can use the
> > +"renesas,usb_extal_only" property for it.
> > +If you connect an oscillator to both the USB_XTAL and USB_EXTAL, this module
> > +is not needed because this is default setting.
> > +
> > +Case 1: An external clock connects to R-Car SoC
> > +	+----------+   +--- R-Car ---------------------+
> > +	|External  |---|USB_EXTAL ---> all usb channels|
> > +	|clock     |   |USB_XTAL                       |
> > +	+----------+   +-------------------------------+
> > +In this case, we need this driver with "usb-extal-only" property.
> > +
> > +Case 2: An oscillator connects to R-Car SoC
> > +	+----------+   +--- R-Car ---------------------+
> > +	|Oscillator|---|USB_EXTAL -+-> all usb channels|
> > +	|          |---|USB_XTAL --+                   |
> > +	+----------+   +-------------------------------+
> > +In this case, we don't need this selector.