On Wed 2015-01-28 09:57:18, Rob Herring wrote:

On Wed, Jan 28, 2015 at 8:33 AM, Nicolas Pitre [off-list ref] wrote:

quoted

On Wed, 28 Jan 2015, Pali Roh?r wrote:

quoted

On Wednesday 28 January 2015 01:50:33 Tony Lindgren wrote:

quoted

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.

I'm fine with that, but we just need to have a standard kernel
userspace interface in addition to something like
/proc/device-tree/bootreason. Perhaps this can be the default
implementation for the watchdog dev. Someday when we decide DT is crap
and have a new boot interface, we'll have people relying on
/proc/device-tree. I hope to be retired when that happens...

Huh. Who thought putting device-tree into /proc was good idea? That
should have gone to /sys, as it is not process related...

Anyway, bootreason does not depend on device-tree, so it should not be
in device-tree specific subdirectory.
									Pavel
-- 
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