linux-kernel - Re: Turris Omnia firmware possibilities [Was: Re: led: hw-trigger, global brightness and multi-colored leds]

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Message-ID: <20180525185007.GA29954@amd>
Date:   Fri, 25 May 2018 20:50:07 +0200
From:   Pavel Machek <pavel@....cz>
To:     Tomas Hlavacek <tomas.hlavacek@....cz>
Cc:     Uwe Kleine-König <uwe@...ine-koenig.org>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: Turris Omnia firmware possibilities [Was: Re: led: hw-trigger,
 global brightness and multi-colored leds]

Hi!

> > On 05/25/2018 12:08 AM, Tomas Hlavacek wrote:
> >> But I also have good news: The FW of the MCU is also OSS (see the repo
> >> in the link (1)). There is a method for flashing the MCU over I2C from
> >> Linux and there is JTAG connector for the MCU, in case un-bricking is
> >> needed. Therefore the LED protocol can be changed to be more sensible
> >> and/or it is even possible to emulate some existing HW LED driver chip
> >> in Omnia MCU and reuse OSS driver for that chip.
> >
> > Yeah, I noticed, but when we start replacing the firmware, we'd need to
> > detect somehow when a machine has an old (or only different) firmware.
> > That would imply a versioning scheme and a generic way to read out the
> > firmware version. (CMD_GET_FW_VERSION_BOOT is already a start, but this
> > doesn't help me if I find an unknown hash.) So a CMD_GET_FW_SOMETHING
> > that yields a version string that is similar to the soname of a library
> > would be great.
> 
> Oh yes, I was actually trying to push rewrite of the FW before the
> production started, but it looked like a redundant work and I rather
> implemented the mentioned rule-breaking LED driver. Another good news
> is that all the produced boards had the same FW image and there were
> no (official and automated) updates so far. I think that in this
> situation it is possible to re-write the firmware it if proves to be
> the best solution for LED driver and fixing other glitches perhaps.
> The only thing we need regarding versions we need is to either check
> that we are upgrading the original version and/or consent from the
> user to rewrite any other version that we might encounter. (If there
> are some user-customized boards around.)

Actually, I believe you should try to write the driver for existing
firmware, and only if you find that performance is not good enough,
change the protocol.

> > Talking about firmware, I wonder if there is firmware supported needed
> > to solve
> > https://wiki.debian.org/InstallingDebianOn/TurrisOmnia#Power_Management
> > . Didn't look into that deeply yet and probably not high prio given that
> > normally the Turris Omnia will just run 7x24h.
> 
> That's right, there is no power-down signalization from the CPU right
> now. Btw. is there any mechanism in kernel to signal over arbitrary
> bus (like I2C) that the host is shutting down and the power can/should
> be cut to CPU in N seconds?

I'm pretty sure kernel can ask the hardware to cut its power. This
sounds like it: drivers/power/reset/gpio-poweroff.c

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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