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authorLinus Walleij <linus.walleij@linaro.org>2015-03-03 09:52:20 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-11-09 14:33:39 -0800
commitd35e462164987724e4a1d20a55351e52181464aa (patch)
tree12e8f8d424094b3ef6ebe6a6f83b2d0cf47a3af6
parente12243dc14b81bc5c4e6e82b0b9ff9911a060a30 (diff)
downloadlinux-linaro-stable-d35e462164987724e4a1d20a55351e52181464aa.tar.gz
MFD/OF: document MFD devices and handle simple-mfd
commit 22869a9eca4ea5b534538d160b68c7aef44e378a upstream. This defines a new compatible option for MFD devices "simple-mfd" that will make the OF core spawn child devices for all subnodes of that MFD device. It is optional but handy for things like syscon and possibly other simpler MFD devices. Since there was no file to put the documentation in, I took this opportunity to make a small writeup on MFD devices and add the compatible definition there. Suggested-by: Lee Jones <lee.jones@linaro.org> Acked-by: Lee Jones <lee.jones@linaro.org> Acked-by: Antoine Tenart <antoine.tenart@free-electrons.com> Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Devicetree <devicetree@vger.kernel.org> Cc: Rob Herring <robh+dt@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Grant Likely <grant.likely@linaro.org> Cc: Pawel Moll <pawel.moll@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Ian Campbell <ijc+devicetree@hellion.org.uk> Cc: Kumar Gala <galak@codeaurora.org> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Cc: Henrik Juul Pedersen <hjp@liab.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--Documentation/devicetree/bindings/mfd/mfd.txt41
-rw-r--r--drivers/of/platform.c1
2 files changed, 42 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/mfd/mfd.txt b/Documentation/devicetree/bindings/mfd/mfd.txt
new file mode 100644
index 000000000000..af9d6931a1a2
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/mfd.txt
@@ -0,0 +1,41 @@
+Multi-Function Devices (MFD)
+
+These devices comprise a nexus for heterogeneous hardware blocks containing
+more than one non-unique yet varying hardware functionality.
+
+A typical MFD can be:
+
+- A mixed signal ASIC on an external bus, sometimes a PMIC (Power Management
+ Integrated Circuit) that is manufactured in a lower technology node (rough
+ silicon) that handles analog drivers for things like audio amplifiers, LED
+ drivers, level shifters, PHY (physical interfaces to things like USB or
+ ethernet), regulators etc.
+
+- A range of memory registers containing "miscellaneous system registers" also
+ known as a system controller "syscon" or any other memory range containing a
+ mix of unrelated hardware devices.
+
+Optional properties:
+
+- compatible : "simple-mfd" - this signifies that the operating system should
+ consider all subnodes of the MFD device as separate devices akin to how
+ "simple-bus" inidicates when to see subnodes as children for a simple
+ memory-mapped bus. For more complex devices, when the nexus driver has to
+ probe registers to figure out what child devices exist etc, this should not
+ be used. In the latter case the child devices will be determined by the
+ operating system.
+
+Example:
+
+foo@1000 {
+ compatible = "syscon", "simple-mfd";
+ reg = <0x01000 0x1000>;
+
+ led@08.0 {
+ compatible = "register-bit-led";
+ offset = <0x08>;
+ mask = <0x01>;
+ label = "myled";
+ default-state = "on";
+ };
+};
diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index a01f57c9e34e..ddf8e42c9367 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -25,6 +25,7 @@
const struct of_device_id of_default_bus_match_table[] = {
{ .compatible = "simple-bus", },
+ { .compatible = "simple-mfd", },
#ifdef CONFIG_ARM_AMBA
{ .compatible = "arm,amba-bus", },
#endif /* CONFIG_ARM_AMBA */