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From: Lei Yu <yulei.sh@bytedance.com>
Date: Wed, 16 Sep 2020 20:13:18 +0800
Message-ID: <CAGm54UEwmNNvx-aCud2S46Aa+A051PDK4KuYUvL=Doqd=nnU9Q@mail.gmail.com>
Subject: Re: Design proposal for dual BMC flash with "golden image"
To: Ivan Mikhaylov <i.mikhaylov@yadro.com>
Cc: Alexander Amelkin <a.amelkin@yadro.com>, openbmc <openbmc@lists.ozlabs.org>
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On Wed, Sep 16, 2020 at 8:02 PM Ivan Mikhaylov <i.mikhaylov@yadro.com> wrote:
> > 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?

In that case, we could manually trigger watchdog by:
1. Enable devmem by appending mem.devmem in bootargs in u-boot, and reboot
2. Now devmem could be used, manually trigger wdt2

Be noted that such case should be rare in the field.
In the lab, we could enable devmem by default and just use it.