linux-kernel - Re: Nokia N900 - audio TPA6130A2 problems

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Date:	Tue, 5 Jan 2016 00:34:12 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	Peter Ujfalusi <peter.ujfalusi@...com>
Cc:	Jarkko Nikula <jarkko.nikula@...mer.com>,
	"Lars-Peter Clausen" <lars@...afoo.de>,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	Pavel Machek <pavel@....cz>,
	Sebastian Reichel <sre@...nel.org>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Tony Lindgren <tony@...mide.com>, Nishanth Menon <nm@...com>,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	merlijn@...zup.org
Subject: Re: Nokia N900 - audio TPA6130A2 problems

On Tuesday 04 August 2015 09:02:39 Peter Ujfalusi wrote:
> On 08/03/2015 09:48 PM, Jarkko Nikula wrote:
> > It is well possible that some regression got introduced to
> > TPA6130A2 I2C communication over the years without nobody than you
> > now notices. We used to do QA back in Meego N900 days but that was
> > pre 3.x kernels.
> 
> No major changes has been done to the tpa driver during the past
> years... I wanted to do some updates, like moving it to regmap, but
> as you said, n900 is the only user (and n9) and I do not feel
> comfortable to hack on a device where I do not have serial
> console... And I'm using the n900 time to time also.
> 
> >> So maybe something similar? Kernel expects that some PM or
> >> regulator parts are initialized, but they are only sometimes?
> >> Just speculation...
> > 
> > I'm thinking the same. I could figure SCL could be stuck low if TPA
> > or some other chip connected to the same I2C bus is without power
> > and is pulling I2C signals down.
> 
> What would happen with the SCL stuck on i2c.2 bus if you remove the
> tpa driver from the kernel? If you remove the other drivers for the
> devices on i2c.2?

Hi Peter and Jarkko! Do you have some code samples for testing? Or 
something else which I can test? This problem is still reproducible on 
more N900 devices and I would like to see it fixed.

-- 
Pali Rohár
pali.rohar@...il.com

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