[PATCH] ARM: /proc/atags: Export also for DT

[Nicolas Pitre]

On Wed, 28 Jan 2015, Pali Rohár wrote:

> On Wednesday 28 January 2015 01:50:33 Tony Lindgren wrote:
> > On omaps, the bootrom passes the bootreason in r1 to the
> > bootloader that can do whatever it wants with it. We could
> > maybe pass it in the kernel cmdline to the watchdog driver
> > for user space?
> > 
> 
> Not truth for N900. Bootreason depends on PRM_RSTST omap 
> register, state of vbat charger pins, time how long was power key 
> pressed, R&D data stored in CAL partition and other undocumented 
> registers for omap HS devices. I already tried to implement at 
> least some subset of it in userspace (or kernel), but it is 
> impossible because NOLO bootloader clear status of PRM_RSTST 
> register.
> 
> There is also copy of PRM_RSTST register stored at address 
> 0x4020FFB8 (tracing data) but that address is rewritten (probably 
> by kernel), so we really cannot implement reading bootreason in 
> kernel.
> 
> But in early stage in uboot it is possible to read 0x4020FFB8 
> address and get some part of bootreason. But still PRM_RSTST is 
> not enough!
> 
> I would be happy if DT kernel can export /proc/atags file with 
> ATAGs passed by bootloader. It would be enough for me. In 
> userspace I can parse content and do what is needed.

What about defining a DT boot reason property instead?
Maybe it already exists?  If not, it's something that could certainly be 
generically used on other platforms too.

Converting the special ATAG into its standard DT equivalent would then 
be trivial and much cleaner overall.


Nicolas