[U-Boot] [PATCH] tegra: trimslice: fix a couple typos

[Marek Vasut]

Dear Stephen Warren,

> On 06/01/2012 12:38 AM, Igor Grinberg wrote:
> > On 05/31/12 19:50, Stephen Warren wrote:
> >> On 05/31/2012 04:13 AM, Marek Vasut wrote:
> >>> Dear Igor Grinberg,
> >>> 
> >>>> On 05/30/12 19:45, Stephen Warren wrote:
> >>>>> From: Stephen Warren <swarren at nvidia.com>
> >>>>> 
> >>>>> Fix the .dts file USB unit addresses not to duplicate each-other.
> >>>>> 
> >>>>> Fix the board name string to indicate the vendor is Compulab not
> >>>>> NVIDIA.
> >>>>> 
> >>>>> Signed-off-by: Stephen Warren <swarren at nvidia.com>
> >>>> 
> >>>> Acked-by: Igor Grinberg <grinberg at compulab.co.il>
> >>> 
> >>> Do we have one copy of the dts files here and one in Linux kernel tree?
> >>> Are they the same?
> >> 
> >> Both U-Boot and the kernel have their own copies of the .dts files.
> >> 
> >> In general, the U-Boot copy would be identical to what's in the kernel,
> >> or a pure subset since mostly the kernel's driver support is more
> >> advanced, so we've added more nodes to the DT.
> >> 
> >> That said, there are unfortunately some bizarre quirks in the way the
> >> U-Boot parses the device tree, such as requiring the /aliases node in
> >> order to enumerate at least some devices, the use of the Tegra clock
> >> binding that hasn't been incorporated into the kernel yet and is used
> >> for both clock and module reset functionality even though it's really
> >> only intended for clock functionality, and various other small
> >> properties that are U-Boot specific (although I forget if we managed to
> >> eliminate these all or not). These all end up causing differences
> >> between the two device tree files:-(
> > 
> > Thanks for the information.
> > 
> > I don't see any problem with having differences between the .dts files
> 
> > in kernel and U-Boot, because the way I see it:
> The issue isn't so much the duplicate files, but differing content.
> 
> The whole point about DT is that it's a pure representation of the
> hardware; there should be no software-dependent design or data in it.
> Put another way, both U-Boot and the Linux kernel (and indeed anything
> else) should expect the DT to be written according to the same
> "bindings" design. This doesn't preclude the U-Boot DT file being a
> strict subset of the kernel file it it needs less information, but what
> is in both should match.

Thanks for clearing it up!

> 
> > Also, IIRC, the intension was to remove the kernel .dts files after
> > "all bootloaders" know to boot the DT kernel...
> 
> I don't believe it's anything to do with bootloaders. Bootloaders are
> already (in the main) expected to provide the DTB to the kernel as a
> separate entity, irrespective of whether the DTB is built by the kernel
> boot process or from some other repository. (Although there is
> CONFIG_APPENDED_DTB to support cases where this isn't possible, it's
> much preferred not to use this). Moving the .dts files out of the kernel
> is more purely about finding a place to put them I think.
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Best regards,
Marek Vasut