On Thu, Jan 15, 2015 at 02:42:23PM +0000, Rob Herring wrote:

On Thu, Jan 15, 2015 at 7:55 AM, Mark Rutland [off-list ref] wrote:

quoted

On Thu, Jan 15, 2015 at 01:52:01PM +0000, Mark Rutland wrote:

quoted

On Wed, Jan 14, 2015 at 08:58:18PM +0000, Suman Anna wrote:

quoted

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. This base id
needs to be unique across multiple IP instances of a hwspinlock
device, so that each hwlock can be represented uniquely in a
system.

The number of locks is represented by 'hwlock-num-locks' property,
and the base id is represented by the 'hwlock-base-id' property.
The args specifier length is dependent on each vendor-specific
implementation and is represented through the '#hwlock-cells'
property. Client users need to use the property 'hwlocks' for
requesting specific lock(s).

Note that the document is named hwlock.txt deliberately to keep
it a bit more generic.

Cc: Rob Herring <robh+dt@kernel.org>
Signed-off-by: Suman Anna <redacted>
---
v7: Revised binding info for hwlock-base-id, it is mandatory now

 .../devicetree/bindings/hwlock/hwlock.txt          | 55 ++++++++++++++++++++++
 1 file changed, 55 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 000000000000..8de7aaf878f9
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwlock/hwlock.txt

@@ -0,0 +1,55 @@
+Generic hwlock bindings
+=======================
+
+Generic bindings that are common to all the hwlock platform specific driver
+implementations.
+
+The validity and need of these common properties may vary from one platform
+implementation to another. The platform specific bindings should explicitly
+state if an optional property is used. Please also 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 property is mandatory for all
+                   platform implementations.
+- 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.
+- hwlock-base-id:  An unique base Id for the locks for a particular hwlock
+                   device. This property is mandatory for all platform
+                   implementations.

This property makes no sense. The ID encoded in the hwlock cells is
relative to the instance (identified by phandle), not global. So the DT
has no global ID space.

Why do you think you need this?

Having looked at the way this proeprty is used, NAK.

If you need to carve up a Linux-internal ID space, do that dynamically.
There is no need for this property.

Better yet, don't create a Linux ID space for this. Everywhere we have
one, we want to get rid of it.

Agreed. A completely opaque token / desc structure would prevent a lot
of potential abuse and save us from painful breakage.

Mark