[POWERPC] add U-Boot bootcount driver.

[Vitaly Bordug]

В Thu, 17 Dec 2009 09:16:07 +0100
Wolfgang Denk <wd at denx.de> пишет:

> Dear Vitaly Bordug,
> 
> 
> repl: bad addresses:
> 	linuxppc-dev at ozlabs.org <linuxppc-dev at ozlabs.org> -- junk
> after local at domain (<) In message <20091216024730.455b90fd at vitb-lp>
> you wrote:
> > 
> > From: Heiko Schocher <hs at denx.de>
> > 
> > This driver provides (read/write) access to the
> > U-Boot bootcounter via PROC FS or sysFS.
> > 
> > in u-boot, it uses a 8 byte mem area (it must hold the value over a
> > soft reset of course), for storing a bootcounter (it counts many
> > soft resets are done, on hard reset it starts with 0). If the
> > bootcountvalue exceeds the value in the env variable "bootlimit",
> > and alternative bootcmd stored in the env variable "altbootcmd" is
> > run.
> > 
> > The bootcountregister gets configured via DTS.
> > for example on the mgsuvd board:
> > 
> > bootcount at 0x3eb0 {
> >                   device_type = "bootcount";
> >                   compatible = "uboot,bootcount";
> >                   reg = <0x3eb0 0x08>;
> >                  };
> > 
> > This driver is tested on the mgcoge(82xx) and mgsuvd(8xx) board.
> > 
> > Signed-off-by: Heiko Schocher <hs at denx.de>
> > Signed-off-by: Wolfgang Denk <wd at denx.de>
> > Signed-off-by: Vitaly Bordyug <vitb at kernel.crashing.org>
> 
> I think it would be good if the text of the commit message could be
> reworked by a native English speaker.
> 
OK. 

> Regarding the subject: it is probably important to point out that this
> driver implements the Linux kernel half of the boot count feature -
> the boot counter can only be reset after it is clear that the
> application has been started and is running correctly, which usually
> can only be determined by the application code itself. Thus the reset
> of the boot counter must be done by application code, which thus needs
> an appropriate driver.
> 
I'll rework the commit message to make it more clear, thanks for the
details!

-Vitaly

> > I think there is no reason not to have this in mainline. Thoughts?
> > And I'm not sure what is right direction to push this - it's
> > representation of u-boot feature in fact, pretty useful tho.
> 
> It's not only useful, it's actually a required feature by the Carrier
> Grade Linux Requirements Definition; see for example document "Carrier
> Grade Linux Requirements Definition Overview V3.0" at
> https://www.linux-foundation.org/images/1/1a/Cgl_req_def_overview_30.pdf
> Page 49:
> 
> 	ID PLT.4.0 (2.3 in v1.1)	Boot Cycle Detection
> 
>         Description: OSDL CGL specifies that carrier grade Linux
>         shall provide support for detecting a repeating reboot cycle
>         due to recurring failures and going to an offline state if
>         this occurs.
> 
> 
> 
> 
> Best regards,
> 
> Wolfgang Denk
>