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

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Date:	Mon, 3 Aug 2015 20:55:34 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Jarkko Nikula <jarkko.nikula@...mer.com>
Cc:	"Lars-Peter Clausen" <lars@...afoo.de>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	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 Monday 03 August 2015 20:48:28 Jarkko Nikula wrote:
> On 08/03/2015 09:17 PM, Pali Rohár wrote:
> > On Monday 03 August 2015 20:03:16 Jarkko Nikula wrote:
> >> Hi
> >> 
> >> On 08/01/2015 01:18 PM, Pali Rohár wrote:
> >>> On Saturday 25 July 2015 15:17:13 Lars-Peter Clausen wrote:
> >>> Hello, your patch did not helped. Problem is still there...
> >> 
> >> For me v4.2-rc5 works, i.e. TPA6130A2 can still play loudly to
> >> headphones. Don't know were there any i2c etc regression before it
> >> or how easy it would be to reproduce.
> > 
> > Did you tested it on Nokia N900? Or other device?
> 
> N900. Seems to be only user of TPA6130A2 in mainline :-)
> 

Great, can you do more tests? I get this error often after I reboot N900 
(without power off) more times. But no idea if this is just "sometimes".

> >> Logs below made me thinking can it be a HW issue? Although if it
> >> is an HW issue it shouldn't work sometimes I guess. Do you have
> >> any earlier well known configuration you could try is it an SW
> >> regression or something else?
> > 
> > Stock Nokia's 2.6.28 kernel works always. With that kernel I have
> > never seen this problem. So I do not think this is HW problem.
> > 
> > This problem is there in more kernel versions, maybe in some older
> > (like v3.5) is was there not so often. But do not remember
> > correctly...
> 
> 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.
> 

Do you still have these pre 3.x kernels? This could be good starting 
point as 2.6.28 kernel is tooo old and heavily patches...

> > Maybe some power management problem? Something is not always
> > initialized correctly?
> > 
> > I remember that there is some problem (maybe in NoLo - Nokia
> > bootloader) that sometimes chainloaded U-Boot (booted via NoLo) is
> > not able to initialize mmc chip (all read operation fails). In
> > U-Boot I added some code to enable some parts in twl4030 regulator
> > and after that mmc is working always...
> > 
> > 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.

We should know which devices are connected to which i2c bus. So maybe 
detecting which i2c device is incorrectly initialized?

-- 
Pali Rohár
pali.rohar@...il.com

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