linux-kernel - Re: [PATCH 1/6] Revert "regulator: core: Handle full constraints systems when resolving supplies"

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Date:	Wed, 30 Sep 2015 20:48:12 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Mark Brown <broonie@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Liam Girdwood <lgirdwood@...il.com>,
	kernel@...gutronix.de, alkml@...gutronix.de
Subject: Re: [PATCH 1/6] Revert "regulator: core: Handle full constraints
 systems when resolving supplies"

On Wed, Sep 30, 2015 at 07:02:13PM +0100, Mark Brown wrote:
> On Wed, Sep 30, 2015 at 03:57:49PM +0200, Sascha Hauer wrote:
> > This reverts commit 9f7e25edb1575a6d2363dc003f9cc09d840657e2.
> > 
> > When a regulator A is registered and is supplied by regulator B which is
> > not yet registered then a regulator_get on regulator A will set the As
> > supply to the dummy regulator. This is not correct, we should return
> > -EPROBE_DEFER instead as done without this patch.
> 
> What makes you say this is not correct?  In a system with fully
> specified supplies if we fail to resolve the supply we know that no
> supply will ever appear and so substitute in the dummy on the assumption
> that there is a supply with no software control.

The situation I'm in is:

		gpc: gpc@...dc000 {
			compatible = "fsl,imx6q-gpc";
			pu-supply = <&reg_pu>;
		};

		reg_pu: regulator-vddpu@140 {
			compatible = "fsl,anatop-regulator";
			vin-supply = <&vddsoc_reg>;
		};

		...

		pmic@58 {
			compatible = "dlg,da9063";
			regulators {
				...
				vddsoc_reg: bcore2 {
					regulator-min-microvolt = <730000>;
					regulator-max-microvolt = <1380000>;
					regulator-always-on;
				};
			};
		};

During boot the fsl,imx6q-gpc is probed and tries to get its regulator.
fsl,anatop-regulator is already registered, the dlg,da9063 is not.  The
call to regulator_get tries to resolve the supply using
regulator_resolve_supply. regulator_resolve_supply then calls
regulator_dev_lookup which returns NULL because the supply (vddsoc_reg)
is specified in the device tree but not yet present. &ret is correctly
filled with -EPROBE_DEFER in this case, but this is ignored. Instead due
to 9f7e25edb157 the dummy regulator is used. This case worked before
9f7e25edb157.

Sascha

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