Design proposal for dual BMC flash with "golden image"

[Ivan Mikhaylov]

On Wed, 2020-09-16 at 18:18 +0800, Lei Yu wrote:
> On Wed, Sep 16, 2020 at 5:55 PM Ivan Mikhaylov <i.mikhaylov at yadro.com> wrote:
> > > For now, we use "devmem" to manipulate the registers for testing purpose.
> > > It's nice to have that driver, but in productions there will be no
> > > need to use devmem nor the ioctl on watchdog, so it's not a must for
> > > us to use the driver.
> > > 
> > 
> > And how you switch safely into golden side in this case?
> > 
> 
> The plan is:
> 1. When the primary flash is broken and u-boot could not be started,
> aspeed will switch to the golden side automatically.
> 2. When the primary flash's u-boot is OK, but the kernel/rofs fails a
> couple of times, the u-boot could detect this and switch to the golden
> side by setting the related registers. See example in
> https://github.com/openbmc/openbmc/blob/master/meta-phosphor/aspeed-layer/recipes-bsp/u-boot/files/0005-config-ast-common-Fall-back-to-secondary-flash-on-fa.patch

That's the standard procedure, I'm saying that you may need the access to the
golden side at any time for different purposes(support engineers, manufacturing
department, some problems in field) and how you can achieve that? With u-boot
env set or manual watchdog trigger?

Thanks.