Hi Rob, On 05/02/2014 09:58 AM, Rob Herring wrote: > On Wed, Apr 30, 2014 at 7:34 PM, Suman Anna <s-anna@xxxxxx> wrote: >> This patch adds the generic common bindings used to represent >> a hwlock device and use/request locks in a device-tree build. >> >> All the platform-specific hwlock driver implementations need the >> number of locks and associated base id for registering the locks >> present within the device with the driver core. The number of locks >> is represented by 'hwlock-num-locks' property in DT bindings. A >> property for base id is not needed in DT binding, as it can be >> satisfied using a phandle + args specifier. The args specifier >> length is dependent on each vendor-specific implementation and >> is represented through the '#hwlock-cells' property. >> >> Note that the document is named hwlock.txt deliberately to keep it >> a bit more generic. >> >> Cc: Rob Herring <robh+dt@xxxxxxxxxx> >> Signed-off-by: Suman Anna <s-anna@xxxxxx> >> --- >> .../devicetree/bindings/hwlock/hwlock.txt | 52 ++++++++++++++++++++++ >> 1 file changed, 52 insertions(+) >> create mode 100644 Documentation/devicetree/bindings/hwlock/hwlock.txt >> >> diff --git a/Documentation/devicetree/bindings/hwlock/hwlock.txt b/Documentation/devicetree/bindings/hwlock/hwlock.txt >> new file mode 100644 >> index 0000000..32381cc >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/hwlock/hwlock.txt >> @@ -0,0 +1,52 @@ >> +Generic hwlock bindings >> +======================= >> + >> +Generic bindings that are common to all the hwlock platform specific driver >> +implementations, the retrieved values are used for registering the device >> +specific parameters with the hwspinlock core. >> + >> +The validity and need of these common properties may vary from one platform >> +implementation to another. The platform specific bindings should explicitly >> +state if a property is mandatory or optional. Please look through the >> +individual platform specific hwlock binding documentations for identifying >> +the applicable properties. >> + >> +Common properties: >> +- #hwlock-cells: Specifies the number of cells needed to represent a >> + specific lock. > > This should never be optional. Thanks for reviewing this. I can add a statement here to make this clear. > >> +- hwlock-num-locks: Number of locks present in a hwlock device. This >> + property is needed on hwlock devices, where the number >> + of supported locks within a hwlock device cannot be >> + read from a register. > > Do you have any users of this? The omap binding doesn't use it. > Wouldn't you typically know this based on the IP block? Similarly you > typically don't have to list how many irqs an interrupt controller > has. The MSM Spinlock driver [1] would be using this, it is waiting on this series to get finalized. It currently defines a custom property, and the number of locks is a generic property that the hwspinlock core uses and is common to different platform implementations, so created the generic property. OMAP doesn't use this because the number is read directly off a IP register. can you also take a look at patches 8 and 12 as they add additional properties based on discussion in [2]. The hwspinlocks are used for arbitration between different initiators on an SoC, and typically would need a SoC-level identifier for each lock. All these properties allow a hwlock to be statically identified and be assigned to a user and its peer user on a different initiator, and not allowing them to be run-time assigned. regards Suman [1] https://lkml.org/lkml/2013/8/14/528 [2] http://marc.info/?l=linux-omap&m=139510004009415&w=2 > > >> + >> +Hwlock Users: >> +============= >> + >> +Nodes that require specific hwlock(s) should specify them using one or more >> +properties, each containing a phandle to the hwlock node and an args specifier >> +value as indicated by #hwlock-cells. Multiple hwlocks can be requested using >> +an array of the phandle and hwlock number specifier tuple. >> + >> +1. Example of a node using a single specific hwlock: >> + >> +The following example has a node requesting a hwlock in the bank defined by >> +the node hwlock1. hwlock1 is a hwlock provider with an argument specifier >> +of length 1. >> + >> + node { >> + ... >> + hwlocks = <&hwlock1 2>; >> + ... >> + }; >> + >> +2. Example of a node using multiple specific hwlocks: >> + >> +The following example has a node requesting two hwlocks, a hwlock within >> +the hwlock device node 'hwlock1' with #hwlock-cells value of 1, and another >> +hwlock within the hwlock device node 'hwlock2' with #hwlock-cells value of 2. >> + >> + node { >> + ... >> + hwlocks = <&hwlock1 2>, <&hwlock2 0 3>; >> + ... >> + }; >> -- >> 1.9.2 >> -- 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
