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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160321145347.GA19391@earth>
Date:	Mon, 21 Mar 2016 15:53:47 +0100
From:	Sebastian Reichel <sre@...nel.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Pali Rohár <pali.rohar@...il.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 Mark,

On Mon, Mar 21, 2016 at 01:45:15PM +0000, Mark Brown wrote:
> On Mon, Mar 21, 2016 at 03:39:15PM +0200, Ivaylo Dimitrov wrote:
> > On 21.03.2016 13:45, Mark Brown wrote:
> 
> > >No, if the voltage is variable we can't tell what the current
> > >constraints are without something telling us so we just don't vary the
> > >voltage until we're told to do this.  If we immediately lower the
> > >voltage to the minimum supported voltage that's going to break things.
> 
> > There are constraints set by the board DTS. Isn't it reasonable the
> > framework to set the voltage to minimum voltage from the dts if the current
> > set one is bellow it?
> 
> Yes, if it's out of bounds for the constraints we should bring it
> up/down to the minimum/maximum (when copying people into a thread it's a
> good idea to explain what the problem you are trying to solve is,
> especially if you're throwing around bodges).

We have this regulator definition in omap3-n900.dts:

&vmmc2 {
	regulator-name = "V28_A";
	regulator-min-microvolt = <2800000>;
	regulator-max-microvolt = <3000000>;
	regulator-always-on; /* due VIO leak to AIC34 VDDs */
};

The regulator is enabled during probe, but the voltage is not
configured. The default reset voltage of the regulator is 2.6V.
So basically when the regulator is enabled, it uses a voltage,
which is out of the DT specified range.

We also have a second problem: If the system has been rebooted from
Nokia's stock kernel the regulator is left in STANDBY mode. Since
the mode is not configured during probe, it results in different
problems. According to my understanding it can be fixed trivially
by adding

&vmmc2 {
    regulator-initial-mode = <2>;
};

-- Sebastian

Download attachment "signature.asc" of type "application/pgp-signature" (820 bytes)