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

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Date:	Wed, 16 Mar 2016 20:21:31 +0200
From:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:	Sebastian Reichel <sre@...nel.org>,
	Pali Rohár <pali.rohar@...il.com>
Cc:	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 16.03.2016 16:47, Sebastian Reichel wrote:
> Hi,
>
> On Wed, Mar 16, 2016 at 02:33:19PM +0100, Pali Rohár wrote:
>> Hi! We found out that tpa6130a2 device is being initialized before
>> i2c_2 bus is initialized. So that is reason why tpa6130a2 fails...
>
> What do you mean by initialize? A call to tpa6130a2_probe()? In that
> case I wonder about client->adapter. Is it NULL?
>

This is (a part of) the log when tpa6130a2 fails to initialize:

Jan  1 08:03:07 Nokia-N900 kernel: [    1.928344] twl 1-0048: PIH (irq 23) chaining IRQs 340..348
Jan  1 08:03:07 Nokia-N900 kernel: [    1.934326] twl 1-0048: power (irq 345) chaining IRQs 348..355
Jan  1 08:03:07 Nokia-N900 kernel: [    2.498504] twl4030_gpio twl4030-gpio: gpio (irq 340) chaining IRQs 356..373
Jan  1 08:03:07 Nokia-N900 kernel: [    2.858215] twl4030_usb 48070000.i2c:twl@48:twl4030-usb: Initialized TWL4030 USB module
Jan  1 08:03:07 Nokia-N900 kernel: [    2.888702] input: twl4030_pwrbutton as /devices/platform/68000000.ocp/48070000.i2c/i2c-1/1-0048/48070000.i2c:twl@48:pwrbutton/input/input0
Jan  1 08:03:07 Nokia-N900 kernel: [    2.903594] input: TWL4030 Keypad as /devices/platform/68000000.ocp/48070000.i2c/i2c-1/1-0048/48070000.i2c:twl@48:keypad/input/input1
Jan  1 08:03:07 Nokia-N900 kernel: [    3.148040] 48070000.i2c:twl@48:madc supply vusb3v1 not found, using dummy regulator
Jan  1 08:03:07 Nokia-N900 kernel: [    6.997985] omap_i2c 48070000.i2c: bus 1 rev3.3 at 2200 kHz
Jan  1 08:03:07 Nokia-N900 kernel: [    7.010528] tpa6130a2 2-0060: Write failed
Jan  1 08:03:07 Nokia-N900 kernel: [    7.015563] omap_i2c 48072000.i2c: bus 2 rev3.3 at 100 kHz
Jan  1 08:03:07 Nokia-N900 kernel: [    7.023742] omap_i2c 48060000.i2c: bus 3 rev3.3 at 400 kHz

Now, it is either tpa6130a2 probe() is called before i2c-2 is
initialized or i2c driver first probes devices on the bus and only then
logs successful probe ("omap_i2c 48072000.i2c: bus 2 rev3.3 at 100 kHz")
in our case.

> ---------------
>
> I just had another look at the driver and I think there is a race
> condition for tpa6130a2_add_controls() and tpa6130a2_stereo_enable().
>
> As far as I can see both functions check for "tpa6130a2_client !=
> NULL". tpa6130a2_client is set before the probe function has finished,
> though. Simplified probe:
>
> ...
> tpa6130a2_client = client;
> set_default_regs();
> acquire_power_gpio();
> acquire_regulator();
> tpa6130a2_power(1); // needs tpa6130a2_client
> check_device();
> tpa6130a2_power(0); // needs tpa6130a2_client
> ...
>
> If tpa6130a2_add_controls() or tpa6130a2_stereo_enable() is called
> after tpa6130a2 probe has started, but before probe has completed,
> tpa6130a2_client is set, but not yet initialized. The race condition
> can be fixed easily by moving the tpa6130a2_client assignment directly
> after the regulator acquisition.
>

I'll try that, thanks.

Regards,
Ivo