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

From: Christophe Leroy
Date: Fri Jun 14 2019 - 06:11:38 EST

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_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:
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.