linux-kernel - Re: [RFC PATCH 1/2] usb: doc: Add bindings for ULPI platform driver

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Date:	Wed, 30 Sep 2015 11:18:03 -0500
From:	Felipe Balbi <balbi@...com>
To:	Rob Herring <robh@...nel.org>
CC:	Subbaraya Sundeep Bhatta <subbaraya.sundeep.bhatta@...inx.com>,
	Peter Chen <peter.chen@...escale.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"balbi@...com" <balbi@...com>, "kishon@...com" <kishon@...com>,
	Punnaiah Choudary Kalluri <punnaia@...inx.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH 1/2] usb: doc: Add bindings for ULPI platform driver

On Thu, Sep 24, 2015 at 11:18:01AM -0500, Rob Herring wrote:
> On Thu, Sep 24, 2015 at 4:26 AM, Subbaraya Sundeep Bhatta
> <subbaraya.sundeep.bhatta@...inx.com> wrote:
> > Hi Peter,
> >
> >> -----Original Message-----
> >> From: Peter Chen [mailto:peter.chen@...escale.com]
> >> Sent: Thursday, September 24, 2015 2:41 PM
> >> To: Subbaraya Sundeep Bhatta
> >> Cc: balbi@...com; devicetree@...r.kernel.org; kishon@...com;
> >> gregkh@...uxfoundation.org; linux-usb@...r.kernel.org; linux-
> >> kernel@...r.kernel.org; Punnaiah Choudary Kalluri; Subbaraya Sundeep Bhatta;
> >> linux-arm-kernel@...ts.infradead.org
> >> Subject: Re: [RFC PATCH 1/2] usb: doc: Add bindings for ULPI platform driver
> >>
> >> On Wed, Sep 23, 2015 at 06:24:01PM +0530, Subbaraya Sundeep Bhatta
> >> wrote:
> >> > This patch adds binding doc info for generic ULPI PHYs platform
> >> > driver.
> >> >
> >> > Signed-off-by: Subbaraya Sundeep Bhatta <sbhatta@...inx.com>
> >> > ---
> >> >  .../devicetree/bindings/usb/ulpi-platform-phy.txt  |   34
> >> ++++++++++++++++++++
> >> >  1 files changed, 34 insertions(+), 0 deletions(-)  create mode 100644
> >> > Documentation/devicetree/bindings/usb/ulpi-platform-phy.txt
> >> >
> >> > diff --git
> >> > a/Documentation/devicetree/bindings/usb/ulpi-platform-phy.txt
> >> > b/Documentation/devicetree/bindings/usb/ulpi-platform-phy.txt
> >> > new file mode 100644
> >> > index 0000000..7b8cbb4
> >> > --- /dev/null
> >> > +++ b/Documentation/devicetree/bindings/usb/ulpi-platform-phy.txt
> >> > @@ -0,0 +1,34 @@
> >> > +Platform driver for generic ULPI PHYs
> >> > +
> >> > +Required properties:
> >> > +- compatible               : Should be "ulpi-phy"
> >> > +- reg                      : Physical base address and size of the USB
> >> > +                     controller registers map to which this PHY
> >> > +                     is connected.
> >> > +- view-port                : Should contain viewport register offset of the
> >> > +                     USB controller to which this PHY is connected Optional
> >> > +properties:
> >> > +- drv-vbus         : required if turning VBUS on/off has to be driven
> >> > +                     by writing to PHY. This feature depends on board
> >> > +                     design.
> >> > +
> >> > +Example:
> >> > +Below example shows the PHY binding for Chipidea USB controller which
> >> > +has ulpi viewport register at 0x0170
> >> > +
> >> > +           usb_phy0: phy0 {
> >> > +                   compatible = "ulpi-phy";
> >> > +                   reg = <0xe0002000 0x1000>;
> >> > +                   view-port = <0x0170>;
> >> > +                   drv-vbus;
> >> > +           };
> >> > +
> >> > +           usb0: usb@...02000 {
> >> > +                        compatible = "chipidea,usb2";
> >> > +                        interrupt-parent = <&intc>;
> >> > +                        interrupts = <0 21 4>;
> >> > +                        reg = <0xe0002000 0x1000>;
> >>
> >> Although just call devm_ioremap twice for the same register region does not
> >> cause any errors, I am not sure if it will has other potential problems. Cc: arm
> >> list.
> >
> > Yes Peter I was also in doubt to call devm_ioremap twice for same register region.
> > devm_ioremap_resource complained hence modified to devm_ioremap. Thanks for
> > adding arm-list.
> 
> Don't put overlapping resources in the DT. Having 2 drivers accessing
> the same registers is not a clean or safe design.

thanks, saves me the trouble of saying the same thing.

Bottom line, if devm_ioremap_resource() fails, you're wrong. Just fix
your driver and move on.

-- 
balbi

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