[PATCH] ARM: OMAP2+: Warn about deprecated legacy booting mode

Pali Rohár pali.rohar at gmail.com
Thu Nov 27 03:32:47 PST 2014

On Thursday 27 November 2014 02:12:04 Tony Lindgren wrote:
> * Pali Rohár <pali.rohar at gmail.com> [141126 15:40]:
> > With enabled CONFIG_ARM_APPENDED_DTB=y file /proc/atags is
> > missing.
> OK I guess it should not be needed for DT based booting.

If I do not enable CONFIG_ARM_APPENDED_DTB=y then kernel is 
booting in legacy mode (not in DT).

> > > The build_tag_list() should parse ATAG_REVISION and then
> > > parse_tag_revision() should copy it to system_rev. Maybe
> > > try adding some printks to see if those functions get
> > > called?
> > 
> > Now I see... Problem is that build_tag_list() is called from
> > convert_to_tag_list() which is called from
> > setup_machine_tags() which is called from setup_arch() only
> > if setup_machine_fdt() call fails. And it fails for *non*
> > DT boot. You can check this chain too.
> Thinking about this probably the best long term solution is
> to pass optional board_revision in the kernel cmdline that
> can be parsed early and copied to system_rev variable.

Not possible. Our bootloader is closed & proprietary. I tried to 
replace it with u-boot I was not able to do that. So we will use 
that Nokia closed bootloader forever and it can provide data only 
in ATAG structure.

> Or if you can think of some other way to get it, we can set
> system_rev in pdata-quirks.c.
> Or maybe add some code to copy the ATAGs somewhere where
> they are out of the way and don't conflict with the device
> tree data? Then we can query ATAG_REVISION from pdata-quirks.c
> and set system_rev.
> Regards,
> Tony

If we are able to read ATAG from pdata-quirks, then we can parse 
it there and fix problems... But I do not know if address of ATAG 
structure is available there...

Pali Rohár
pali.rohar at gmail.com
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