On Tue, 03 Mar 2015, Rob Herring wrote: > On Tue, Mar 3, 2015 at 3:32 AM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > > 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@xxxxxxxxxx> > > Cc: Arnd Bergmann <arnd@xxxxxxxx> > > Cc: Devicetree <devicetree@xxxxxxxxxxxxxxx> > > Cc: Rob Herring <robh+dt@xxxxxxxxxx> > > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > > Cc: Grant Likely <grant.likely@xxxxxxxxxx> > > Cc: Pawel Moll <pawel.moll@xxxxxxx> > > Cc: Mark Rutland <mark.rutland@xxxxxxx> > > Cc: Ian Campbell <ijc+devicetree@xxxxxxxxxxxxxx> > > Cc: Kumar Gala <galak@xxxxxxxxxxxxxx> > > Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx> > > --- > > I make the patch to the OF core in this one, it makes much more sense since > > it's a oneliner > > > > Lee: this is a (tested!) implementation of your suggestion for simple-mfd. > > If you can eventually ACK this from the MFD side, I think it should be > > funneled through the ARM SoC tree. > > > > Grant/Rob: if either of you can ACK the change to the OF core likewise it can > > be taken through ARM SoC. > > > > DT binings maintainers: there is some background discussion on this here: > > http://marc.info/?l=linux-arm-kernel&m=142486676603889&w=2 > > http://marc.info/?l=devicetree&m=142166313621469&w=2 > > --- > > Documentation/devicetree/bindings/mfd/mfd.txt | 40 +++++++++++++++++++++++++++ > > drivers/of/platform.c | 1 + > > 2 files changed, 41 insertions(+) > > create mode 100644 Documentation/devicetree/bindings/mfd/mfd.txt > > > > diff --git a/Documentation/devicetree/bindings/mfd/mfd.txt b/Documentation/devicetree/bindings/mfd/mfd.txt > > new file mode 100644 > > index 000000000000..cc057438abe8 > > --- /dev/null > > +++ b/Documentation/devicetree/bindings/mfd/mfd.txt > > @@ -0,0 +1,40 @@ > > +Multi-Function Devices (MFD) > > + > > +These devices comprise a nexus for heterogeneous hardware blocks spawning > > +multiple child devices. > > + > > +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 registers. > > + > > +Optional properties: > > + > > +- compatible : "simple-mfd" - this signifies that the operating system should > > + spawn child devices for all the subnodes of the MFD device akin to how > > + "simple-bus" inidicates when to spawn children for a simple memory-mapped > > + bus. For more complex devices, when the nexus driver has to probe registers > > + to figure out what children exist etc, this should not be used. In the latter > > + case the child devices will be instantiated by the operating system. > > If you point of_platform_populate to the parent node, it should > instantiate all children regardless of "simple-bus" or any other > match. The match is to probe the grandchildren. I could be mistaken, > but that's how it works at the root level. You don't have a driver > probe for the parent, so you want the top level of_platform_populate > call to instantiate these devices? > > Why does simple-bus not work for you? After all, it is not > "simple-memory-map-bus." simple-bus does 'work'. There are even some (3 I think) platforms actively making use of it. However, there was some controversy over using it, as syscon isn't really a bus. -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
