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

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Date:	Thu, 17 Mar 2016 09:56:22 +0200
From:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:	Sebastian Reichel <sre@...nel.org>
Cc:	Grygorii Strashko <grygorii.strashko@...com>,
	Pali Rohár <pali.rohar@...il.com>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	Jarkko Nikula <jarkko.nikula@...mer.com>,
	Tony Lindgren <tony@...mide.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 02:49, Sebastian Reichel wrote:
>
> mh both, the power gpio is turned off in tpa6130a2_power(0). I guess
> if you don't see the problem during probe() everything works?
>
> I have another idea though: In opposit to the gpio, the regulator
> may also be referenced by something else/already enabled. I guess
> adding a sleep after the regulator_enable() is worth a try.
>
> Also I wonder if the same happens, if you avoid having the module
> available during boot and instead load it once everything has
> settled. That would rule out any side-effects of other modules
> being probed on the same i2c bus.


Well, I think I've figured it out - input pullups are not enabled
on i2c bus pins, in stock kernel we have:

./devmem2 0x480021BC
Value at address 0x480021BC (0x4001f1bc): 0x1180118

./devmem2 0x480021C0
Value at address 0x480021C0 (0x4001f1c0): 0x1180118

in mainline

./devmem2 0x480021BC
Value at address 0x480021BC (0xb6ff01bc): 0x1000100

./devmem2 0x480021C0
Value at address 0x480021C0 (0xb6f6d1c0): 0x1000100

I wonder how i2c devices work at all :)

Will fix the board DTS file later on an will report

Regards,
Ivo