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Date: Thu, 28 Sep 2023 15:07:25 +0800
From: Tzung-Bi Shih <tzungbi@kernel.org>
To: Rob Barnes <robbarnes@google.com>
Cc: chrome-platform@lists.linux.dev, gwendal@chromium.org,
	groeck@chromium.org
Subject: Re: [PATCH] drivers/cros_ec: Reduce log polling period to 2s
Message-ID: <ZRUmLWf6COwE8gtv@google.com>
References: <20230921141935.3973069-1-robbarnes@google.com>
 <ZQ6k1K//086Ptqg0@google.com>
 <CA+Dqm30KGiSVnJ+z=ToT_i3xS6dN5+opCHbp-9tfd+ZqxdgJQA@mail.gmail.com>
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In-Reply-To: <CA+Dqm30KGiSVnJ+z=ToT_i3xS6dN5+opCHbp-9tfd+ZqxdgJQA@mail.gmail.com>

On Tue, Sep 26, 2023 at 12:57:22PM -0600, Rob Barnes wrote:
> On Sat, Sep 23, 2023 at 2:42 AM Tzung-Bi Shih <tzungbi@kernel.org> wrote:
> >
> > On Thu, Sep 21, 2023 at 02:19:35PM +0000, Rob Barnes wrote:
> > > 2. Yields more recent logs prior to a crash, facilitating easier debugging.
> >
> > The approach depends on multiple parties before a system reboot: EC reports
> > on panic, AP sends EC commands for reading the logs, userland programs
> > (e.g. timberslide) write the logs to filesystem, and filesystem
> > synchronization.  If anyone in the path didn't work in time, the logs
> > disappear.
> 
> This change is just affecting the continuous polling period of the
> cros_ec driver.
> Syncing the log immediately after a panic is a separate path and will only work
> when EC supports system safe mode recovery, most don't.

I guess I misunderstood.  Is the understanding "EC can't respond to further
host commands from AP after EC crashed unless some more special supports
(e.g. system safe mode)" correct?

If yes, how about after EC reported a panic but before EC crashed?  Can EC
respond to host commands during the period?

> The hope with shortening the period is that cros_ec.previous will contain more
> relevant logs after a crash, even when safe mode isn't enabled.

What is current approach for getting EC crash dumps/logs from AP?  If the
system didn't save them before system reset, are they available after next
boot?