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

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Date:	Tue, 4 Aug 2015 10:02:39 +0300
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Jarkko Nikula <jarkko.nikula@...mer.com>,
	Pali Rohár <pali.rohar@...il.com>
CC:	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>
Subject: Re: Nokia N900 - audio TPA6130A2 problems

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?

-- 
Péter
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