[POWERPC] cpm: Describe multi-user ram in its own device node.

The way the current CPM binding describes available multi-user (a.k.a.
dual-ported) RAM doesn't work well when there are multiple free regions,
and it doesn't work at all if the region doesn't begin at the start of
the muram area (as the hardware needs to be programmed with offsets into
this area).  The latter situation can happen with SMC UARTs on CPM2, as its
parameter RAM is relocatable, u-boot puts it at zero, and the kernel doesn't
support moving it.

It is now described with a muram node, similar to QE.  The current CPM
binding is sufficiently recent (i.e. never appeared in an official release)
that compatibility with existing device trees is not an issue.

The code supporting the new binding is shared between cpm1 and cpm2, rather
than remain separated.  QE should be able to use this code as well, once
minor fixes are made to its device trees.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

1 files changed, 36 insertions, 4 deletions

diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt
index c36dcd2fbdc4..ce5d67f5cb5c 100644
--- a/Documentation/powerpc/booting-without-of.txt
+++ b/Documentation/powerpc/booting-without-of.txt
@@ -1861,9 +1861,7 @@ platforms are moved over to use the flattened-device-tree model.
 
    Properties:
    - compatible : "fsl,cpm1", "fsl,cpm2", or "fsl,qe".
-   - reg : The first resource is a 48-byte region beginning with
-           CPCR.  The second is the available general-purpose
-           DPRAM.
+   - reg : A 48-byte region beginning with CPCR.
 
    Example:
         cpm@119c0 {
@@ -1871,7 +1869,7 @@ platforms are moved over to use the flattened-device-tree model.
                 #size-cells = <1>;
                 #interrupt-cells = <2>;
                 compatible = "fsl,mpc8272-cpm", "fsl,cpm2";
-                reg = <119c0 30 0 2000>;
+                reg = <119c0 30>;
         }
 
    ii) Properties common to mulitple CPM/QE devices
@@ -2017,6 +2015,40 @@ platforms are moved over to use the flattened-device-tree model.
                 fsl,cpm-command = <2e600000>;
         };
 
+   viii) Multi-User RAM (MURAM)
+
+   The multi-user/dual-ported RAM is expressed as a bus under the CPM node.
+
+   Ranges must be set up subject to the following restrictions:
+
+   - Children's reg nodes must be offsets from the start of all muram, even
+     if the user-data area does not begin at zero.
+   - If multiple range entries are used, the difference between the parent
+     address and the child address must be the same in all, so that a single
+     mapping can cover them all while maintaining the ability to determine
+     CPM-side offsets with pointer subtraction.  It is recommended that
+     multiple range entries not be used.
+   - A child address of zero must be translatable, even if no reg resources
+     contain it.
+
+   A child "data" node must exist, compatible with "fsl,cpm-muram-data", to
+   indicate the portion of muram that is usable by the OS for arbitrary
+   purposes.  The data node may have an arbitrary number of reg resources,
+   all of which contribute to the allocatable muram pool.
+
+   Example, based on mpc8272:
+
+        muram@0 {
+                #address-cells = <1>;
+                #size-cells = <1>;
+                ranges = <0 0 10000>;
+
+                data@0 {
+                        compatible = "fsl,cpm-muram-data";
+                        reg = <0 2000 9800 800>;
+                };
+        };
+
    m) Chipselect/Local Bus
 
    Properties: