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

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Date:	Thu, 24 Sep 2015 11:18:01 -0500
From:	Rob Herring <robh@...nel.org>
To:	Subbaraya Sundeep Bhatta <subbaraya.sundeep.bhatta@...inx.com>
Cc:	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 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.

Rob
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