[U-Boot] [PATCH 1/3] dm: dts: ls2085a: Bring in ls2085a dts files from linux kernel

[Albert ARIBAUD]

Hello Sharma,

On Wed, 8 Jul 2015 10:31:45 +0000, Sharma Bhupesh
<bhupesh.sharma at freescale.com> wrote:
> Hi Albert
> 
> > -----Original Message-----
> > From: Albert ARIBAUD [mailto:albert.u.boot at aribaud.net]
> > Sent: Wednesday, July 08, 2015 2:50 PM
> > To: Sharma Bhupesh-B45370
> > Cc: Wang Haikun-B53464; Bin Meng; Russell King; Mark Rutland; Sun York-
> > R58495; Kushwaha Prabhakar-B32579; u-boot at lists.denx.de
> > Subject: Re: [U-Boot] [PATCH 1/3] dm: dts: ls2085a: Bring in ls2085a dts
> > files from linux kernel
> > 
> > Hello Sharma,
> > 
> > On Wed, 8 Jul 2015 07:31:47 +0000, Sharma Bhupesh
> > <bhupesh.sharma at freescale.com> wrote:
> > > > -----Original Message-----
> > > > From: U-Boot [mailto:u-boot-bounces at lists.denx.de] On Behalf Of Wang
> > > > Haikun On 7/8/2015 3:13 PM, Bin Meng wrote:
> > > > > Hi,
> > > > >
> > > > > On Wed, Jul 8, 2015 at 2:51 PM, Wang Haikun
> > > > > <Haikun.Wang at freescale.com>
> > > > wrote:
> > > > >> On 6/26/2015 7:53 PM, Haikun Wang wrote:
> > > > >>> From: Haikun Wang <Haikun.Wang at freescale.com>
> > > > >>>
> > > > >>> Bring in required device tree files for ls2085a from Linux.
> > > > >>> These are initially unchanged and have a number of pieces not
> > > > >>> needed
> > > > by U-Boot.
> > > > >> Hi Simon,
> > > > >>
> > > > >> I got below comment when review this patch internal.
> > > > >> Please help me confirm.
> > > > >>
> > > > >> "For new platforms like ARM64, it was discussed to not duplicate
> > > > >> the DTS in u-boot and Linux, simply because that will break
> > > > >> compatibility with other bootloaders like Linaro's BootMonitor
> > > > >> and UEFI bootloader, which do not place the DTS in the
> > > > >> bootloader. Also in near future, with DTS being replaced by ACPI
> > > > >> gradually for ARM64 platforms, it was discussed that in a longer
> > > > >> run it would be beneficial to move DTS out of both u-boot and
> > Linux and maintain it as a separate tree."
> > > > >>
> > > > >
> > > > > I think UEFI + ACPI is only required for ARMv8 servers, not for
> > > > > all
> > > > > ARMv8 processors. Is ls2085a a processor targeting the server
> > market?
> > > > No, at least it's not our major market.
> > > > I want to know whether we have made a conclusion that u-boot will
> > > > not add
> > > > Arm64 dts files?
> > >
> > > Adding Russell and Mark for their thoughts.
> > >
> > > AFAIK there were discussions to generate common DTS files for PPC and
> > > ARM platforms, where it was discussed that in a longer run it would be
> > > beneficial to move DTS out of both u-boot and Linux and maintain it as
> > a separate tree.
> > 
> > This might be what happens in the long term (and I pretty much agree with
> > having DTS common to, and separate from, any project that uses them even
> > though that means yet one more configuration item to manage at the full
> > project delivery level), but precisely because it is a long term goal, it
> > is not what's going on right now.
> > 
> > In the interim, and AFAIAC, I'm fine with DTS files living in U-Boot.
> > And I'd be finer yet with a simple way to specify where the DTS files can
> > be searched for at build time, using e.g. an env var, something
> > like:
> > 
> >   DTC_PATH = "/home/dev/linux/arch/arm/boot/dtc" tools/buildman/...
> > 
> > I believe this would be quite easy to implement in both U-Boot and Linux
> > with dtc_cpp_flags, by passing DTC_PATH as a -I option.
> > 
> > One could even specify a set of paths, which would produce several -I
> > options, for instance making dtc search first in U-Boot's own repo, then
> > in the standalone DTS files projects repo (once a standalone DTS files
> > project exists, that is). Looking in U-Boot first would allow using U-
> > boot as a staging area for new DTS files until the standalone DTS project
> > picks them up.
> > 
> 
> I am in agreement, with what you said above, but we must be careful to not introduce
> any dependencies in Linux dts assuming that the u-boot dts will fix them up or implement
> them. With Linaro BootMonitor and UEFI like bootloaders, which don't have the comprehensive
> DTS infrastructure, nor the dts fixup infrastructure, we should be pushing u-boot
> dts changes back to the Linux dts, to make sure that Linux boots fine with other
> ARM64 bootloaders like UEFI.

Agreed: DTS files should be designed to work with all projects that use
them, even DTS files temporarily provided within U-Boot.

> Regards,
> Bhupesh

Amicalement,
-- 
Albert.