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

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Message-Id: <201603121342.33099@pali>
Date:	Sat, 12 Mar 2016 13:42:33 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	Sebastian Reichel <sre@...nel.org>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	Jarkko Nikula <jarkko.nikula@...mer.com>,
	Tony Lindgren <tony@...mide.com>
Cc:	"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>,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	merlijn@...zup.org
Subject: Re: Nokia N900 - audio TPA6130A2 problems

On Sunday 06 March 2016 16:23:39 Sebastian Reichel wrote:
> Hi Pali,
> 
> On Tue, Jan 05, 2016 at 12:34:12AM +0100, Pali Rohár wrote:
> > On Tuesday 04 August 2015 09:02:39 Peter Ujfalusi wrote:
> > > 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?
> > 
> > Hi Peter and Jarkko! Do you have some code samples for testing? Or
> > something else which I can test? This problem is still reproducible
> > on more N900 devices and I would like to see it fixed.
> 
> I have not seen your error with N900, but while working on N950 I
> noticed similar problems when I added lp5523. I think the lp5523
> reset routine locks up the omap i2c controller, since the lp5523
> will stop responding in the middle of an ongoing communication:
> 
> static void lp55xx_reset_device(struct lp55xx_chip *chip)
> {
> 	struct lp55xx_device_config *cfg = chip->cfg;
> 	u8 addr = cfg->reset.addr;
> 	u8 val  = cfg->reset.val;
> 
> 	/* no error checking here because no ACK from the device after reset
> */ lp55xx_write(chip, addr, val);
> }
> 
> Since tpa6130a2 is on the same i2c bus, it would be affected by
> this. You can check this by just commenting out the call to
> lp55xx_reset_device() in the probe function, since it's not
> needed on N900 (chip reset is done via enable gpio anyways).
> 
> I'm pretty sure, there were no bus lock problems when I added
> lp5523 to N900 dts, so this having problems with this is probably
> a regression in the omap-i2c driver.
> 
> -- Sebastian

Hi Sebastian! Commenting calling lp55xx_reset_device function did not 
helped. Still getting that error.

Tony, Peter, Jarkko: can you reproduce this problem? I'm really stucked 
here... do not know where is problem or how to fix it. What we know that 
it happens when rebooting from stock Nokia kernel (2.6.28) to upstream.

-- 
Pali Rohár
pali.rohar@...il.com

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