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

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Message-ID: <56EAC62E.7020302@gmail.com>
Date:	Thu, 17 Mar 2016 16:58:54 +0200
From:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	Sebastian Reichel <sre@...nel.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	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>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Nishanth Menon <nm@...com>, merlijn@...zup.org
Subject: Re: Nokia N900 - audio TPA6130A2 problems

Hi,

On 17.03.2016 16:32, Tony Lindgren wrote:
>
> Seems like a bug to me. My bets are on the deferred probe related
> Peter posted.
>

I will test Peter's patch as well, however I really doubt internal 
pull-ups enabled by Nokia to be a bug - keep in mind there are (or at 
least were) enough devices on the field for such a bug to not remain 
unnoticed, esp if it directly affects the signal quality over the i2c bus.

>
> You can calculate the parallel resistor value of the weak internal
> pull with the 1k external pull :)

Sure :)

> If the i2c line pulls are wrong
> the signal quality won't match the spec and you will be getting
> i2c bus errors. If you can read and write to the i2c chip, this
> is not the issue.
>

And it seems stock kernel can read/write without problems with those 
pull-ups enabled.

However, lets continue the discussion after I have tested both the 
Peter's patch and internal pull-ups enabled.

Thanks,
Ivo