linux-kernel - sdmmc controllers without vmmc regulator

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Date:	Fri, 24 Feb 2012 13:35:08 -0800
From:	Stephen Warren <swarren@...dia.com>
To:	"Mark Brown (broonie@...nsource.wolfsonmicro.com)" 
	<broonie@...nsource.wolfsonmicro.com>,
	"Liam Girdwood (lrg@...com)" <lrg@...com>,
	Chris Ball <cjb@...top.org>
CC:	Marek Szyprowski <m.szyprowski@...sung.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: sdmmc controllers without vmmc regulator

sdhci_add_host() calls regulator_get(..., "vmmc"), which under device-
tree calls of_get_regulator(), which contains:

	regnode = of_parse_phandle(dev->of_node, prop_name, 0);

	if (!regnode) {
		dev_warn(dev, "%s property in node %s references invalid phandle",
				prop_name, dev->of_node->full_name);
		return NULL;
	}

Thus if the vmmc-supply property is missing, because a board has no
regulator for a particular SD controller (power is always on), then
the warning is printed.

Can we eliminate this warning in of_get_regulator(), and let clients
Control whether they warn when a regulator isn't found, if they think
one is mandatory? I think I'd prefer this option; it's consistent with
the non-DT path in regulator_dev_lookup().

Or, should I set up dummy regulators in device tree to cover this case,
such that an SD controller's vmmc-supply always points at a valid phandle.
In which case, I'd have to add DT support to the dummy regulator.

Thanks.

-- 
nvpublic

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