Re: [PATCH] powerpc: Enable kernel XZ compression option on PPC_85xx

[Christophe Leroy]

Le 13/06/2019 Ã 13:42, Michael Ellerman a ÃcritÂ:
> Daniel Axtens <dja@xxxxxxxxxx> writes:
> > Pawel Dembicki <paweldembicki@xxxxxxxxx> writes:
> >
> > > Enable kernel XZ compression option on PPC_85xx. Tested with
> > > simpleImage on TP-Link TL-WDR4900 (Freescale P1014 processor).
> > >
> > > Suggested-by: Christian Lamparter <chunkeey@xxxxxxxxx>
> > > Signed-off-by: Pawel Dembicki <paweldembicki@xxxxxxxxx>
> > > ---
> > >   arch/powerpc/Kconfig | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > > index 8c1c636308c8..daf4cb968922 100644
> > > --- a/arch/powerpc/Kconfig
> > > +++ b/arch/powerpc/Kconfig
> > > @@ -196,7 +196,7 @@ config PPC
> > >   	select HAVE_IOREMAP_PROT
> > >   	select HAVE_IRQ_EXIT_ON_IRQ_STACK
> > >   	select HAVE_KERNEL_GZIP
> > > -	select HAVE_KERNEL_XZ			if PPC_BOOK3S || 44x
> > > +	select HAVE_KERNEL_XZ			if PPC_BOOK3S || 44x || PPC_85xx
> >
> > (I'm not super well versed in the compression stuff, so apologies if
> > this is a dumb question.) If it's this simple, is there any reason we
> > can't turn it on generally, or convert it to a blacklist of platforms
> > known not to work?
>
> For some platforms enabling XZ requires that your u-boot has XZ support,
> and I'm not very clear on when that support landed in u-boot and what
> boards have it. And there are boards out there with old/custom u-boots
> that effectively can't be updated.

I don't think that it has anything to do with u-boot.
AFAIK, today's mainline U-boot only supports GZIP (by default) and the 
following optional ones: LZO, LZMA, LZ4.

If we want to set additional compression types for u-boot, it is not 
enough to select HAVE_KERNEL_XXXX, we also have to update uImage 
generation scripts.

See the series I sent some time ago: 
https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=104153
I'll resent it without bzip2 as today's uboot doesn't support bzip2 anymore.

> But as a server guy I don't really know the details of all that very
> well. So if someone tells me that we should enable XZ for everything, or
> as you say just black list some platforms, then that's fine by me.

I guess we first need to understand how this is used.

Christophe