[PATCH 5/6] powerpc/boot: add xz support to the wrapper script

[Michael Ellerman]

Oliver O'Halloran <oohall at gmail.com> writes:

> This modifies the script so that the -Z option takes an argument to
> specify the compression type. It can either be 'gz', 'xz' or 'none'.
> The legazy --no-gzip and -z options are still supported and will set
> the compression to none and gzip respectively, but they are not
> documented.
>
> Only xz -6 is used for compression rather than xz -9. Using compression
> levels higher than 6 requires the decompressor to build a large (64MB)
> dictionary when decompressing and some environments cannot satisfy large
> allocations (e.g. POWER 6 LPAR partition firmware).

This isn't working for me on machines that use uImage.

That's the "uboot" case in wrapper, where we do:

    ${MKIMAGE} -A ppc -O linux -T kernel -C gzip -a $membase -e $membase \
	$uboot_version -d "$vmz" "$ofile"

ie. we tell mkimage that we're using gzip compression, regardless of
whether we actually are.

That leads to something like:

  ## Booting kernel from Legacy Image at 01000000 ...
     Image Name:   Linux-4.8.0-rc5-compiler_gcc-6.2
     Image Type:   PowerPC Linux Kernel Image (gzip compressed)
     Data Size:    3381044 Bytes = 3.2 MiB
     Load Address: 00000000
     Entry Point:  00000000
     Verifying Checksum ... OK
  ## Flattened Device Tree blob at 0c000000
     Booting using the fdt blob at 0xc000000
     Uncompressing Kernel Image ... Error: Bad gzipped data
  gzip compressed: uncompress error -1
  Must RESET board to recover


So you'll need to do some juggling so you can pass the right argument
for -C to mkimage.

cheers