linux-kernel - Re: Nokia N900 sound driver and ECI GPIOs

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Message-ID: <2036063.jAbaHqGlp2@saturn>
Date:   Mon, 02 Jan 2017 22:05:39 +0100
From:   joerg Reisenweber <joerg@...nmoko.org>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     Aaro Koskinen <aaro.koskinen@....fi>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Jarkko Nikula <jarkko.nikula@...mer.com>,
        Tony Lindgren <tony@...mide.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Nishanth Menon <nm@...com>, Sebastian Reichel <sre@...nel.org>,
        Pavel Machek <pavel@....cz>,
        Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Nokia N900 sound driver and ECI GPIOs

On Mon 02 January 2017 21:01:01 Pali Rohár wrote:
> On Monday 02 January 2017 19:49:45 Aaro Koskinen wrote:
> > The schematic shows ECI(5:0), but only 3 are connected/used. There
> > were 3 other GPIOs reserved but not used in the final product.
> 
> Are you sure that this is truth (maybe you have some information)? Or
> you just looked at schematic and deduced this observation (as other
> people too)?
> 
> Joerg already told us that RX51 schematic does not 100% match production
> N900 and e.g. there is missing UART3 pins...

We found this, see https://irclog.whitequark.org/neo900/2017-01-01 (has a lot 
of possibly useful references/links)
The question is if pin AA3 aka GPIO_178 is actually NotConnected in N900 or 
it's just an omission in schematics and there's actually some more 'stealth 
hardware' in N900 that doesn't show up in docs, just like the testpoint UART 
console http://wiki.maemo.org/N900_Hardware_Hacking#Debug_ports which also are 
missing in schematics.

> What we know that gpio 178 is *already* controlled and changed by
> production Nokia kernel running on production N900 devices (as I wrote
> in first email).

I could use one of the unpopulated N900 PCB and solder a wire to the OMAP AA3 
pad, then try to make sure it's not connected to anything, or if it is then 
find out about the details of this.
But I'm reluctant to do this, since it's an error prone and (in case of N/C) 
not verifiable procedure, so I'd appreciate any further info, whether from 
historical anecdote or from sourcecode review and conclusions, regarding that.

cheers
jOERG
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