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

From: Rob Herring
Date: Thu Sep 24 2015 - 12:18:26 EST


On Thu, Sep 24, 2015 at 4:26 AM, Subbaraya Sundeep Bhatta
<subbaraya.sundeep.bhatta@xxxxxxxxxx> wrote:
> Hi Peter,
>
>> -----Original Message-----
>> From: Peter Chen [mailto:peter.chen@xxxxxxxxxxxxx]
>> Sent: Thursday, September 24, 2015 2:41 PM
>> To: Subbaraya Sundeep Bhatta
>> Cc: balbi@xxxxxx; devicetree@xxxxxxxxxxxxxxx; kishon@xxxxxx;
>> gregkh@xxxxxxxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx; linux-
>> kernel@xxxxxxxxxxxxxxx; Punnaiah Choudary Kalluri; Subbaraya Sundeep Bhatta;
>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>> 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@xxxxxxxxxx>
>> > ---
>> > .../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@e0002000 {
>> > + 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/