Re: [PATCH 9/9] usb: {ohci,ehci}-platform: Use new OF big-endian helper function

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On Wed, 26 Nov 2014, Kevin Cernekee wrote:

> On Wed, Nov 26, 2014 at 7:14 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> >> diff --git a/Documentation/devicetree/bindings/usb/usb-ehci.txt b/Documentation/devicetree/bindings/usb/usb-ehci.txt
> >> index 43c1a4e..9505c31 100644
> >> --- a/Documentation/devicetree/bindings/usb/usb-ehci.txt
> >> +++ b/Documentation/devicetree/bindings/usb/usb-ehci.txt
> >> @@ -12,6 +12,8 @@ Optional properties:
> >>   - big-endian-regs : boolean, set this for hcds with big-endian registers
> >>   - big-endian-desc : boolean, set this for hcds with big-endian descriptors
> >>   - big-endian : boolean, for hcds with big-endian-regs + big-endian-desc
> >> + - native-endian : boolean, enables big-endian-regs + big-endian-desc
> >> +   iff the kernel was compiled for big endian
> >
> > Is this really a property of the hardware?  It appears to depend on the
> > kernel configuration.  As such, is it appropriate for DT?
> 
> Yes, the peripheral registers automatically adjust their endianness to
> match the CPU.  So if the CPU is running an LE kernel, the peripheral
> needs to be accessed in LE mode; if the CPU is running a BE kernel,
> the peripheral needs to be accessed in BE mode.

Okay, then:

Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>

But you might want to update the description slightly to say:

 - native-endian : boolean, enables big-endian-regs + big-endian-desc
   iff the CPU is running in big-endian mode

It's a very minor distinction, since you can't run a kernel that was 
compiled for little endian if the CPU is running in big-endian mode, 
but this makes it clear that you're talking about the hardware rather 
than the software.

Alan Stern

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