memory: mvebu-devbus: add a devbus, keep-config property

[firefly-linux-kernel-4.4.55.git] / Documentation / devicetree / bindings / memory-controllers / mvebu-devbus.txt

diff --git a/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt b/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
index 653c90c34a71bdeae7f6029a4c4e0106300a98c8..1ee3bc09f31982d3bf554e22972e4a6768920501 100644 (file)
--- a/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
+++ b/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
@@ -6,10 +6,11 @@ The actual devices are instantiated from the child nodes of a Device Bus node.
 
 Required properties:
 
- - compatible:          Currently only Armada 370/XP SoC are supported,
-                        with this compatible string:
+ - compatible:          Armada 370/XP SoC are supported using the
+                        "marvell,mvebu-devbus" compatible string.
 
-                        marvell,mvebu-devbus
+                        Orion5x SoC are supported using the
+                        "marvell,orion-devbus" compatible string.
 
  - reg:                 A resource specifier for the register space.
                         This is the base address of a chip select within
@@ -22,7 +23,14 @@ Required properties:
                         integer values for each chip-select line in use:
                         0 <physical address of mapping> <size>
 
-Mandatory timing properties for child nodes:
+Optional properties:
+
+ - devbus,keep-config   This property can optionally be used to keep
+                        using the timing parameters set by the
+                        bootloader. It makes all the timing properties
+                        described below unused.
+
+Timing properties for child nodes:
 
 Read parameters:
 
@@ -30,21 +38,26 @@ Read parameters:
                         drive the AD bus after the completion of a device read.
                         This prevents contentions on the Device Bus after a read
                         cycle from a slow device.
+                        Mandatory, except if devbus,keep-config is used.
 
- - devbus,bus-width:    Defines the bus width (e.g. <16>)
+ - devbus,bus-width:    Defines the bus width, in bits (e.g. <16>).
+                        Mandatory, except if devbus,keep-config is used.
 
  - devbus,badr-skew-ps: Defines the time delay from from A[2:0] toggle,
                         to read data sample. This parameter is useful for
                         synchronous pipelined devices, where the address
                         precedes the read data by one or two cycles.
+                        Mandatory, except if devbus,keep-config is used.
 
  - devbus,acc-first-ps: Defines the time delay from the negation of
                         ALE[0] to the cycle that the first read data is sampled
                         by the controller.
+                        Mandatory, except if devbus,keep-config is used.
 
  - devbus,acc-next-ps:  Defines the time delay between the cycle that
                         samples data N and the cycle that samples data N+1
                         (in burst accesses).
+                        Mandatory, except if devbus,keep-config is used.
 
  - devbus,rd-setup-ps:  Defines the time delay between DEV_CSn assertion to
                        DEV_OEn assertion. If set to 0 (default),
@@ -52,6 +65,8 @@ Read parameters:
                         This parameter has no affect on <acc-first-ps> parameter
                         (no affect on first data sample). Set <rd-setup-ps>
                         to a value smaller than <acc-first-ps>.
+                        Mandatory for "marvell,mvebu-devbus" compatible string,
+                        except if devbus,keep-config is used.
 
  - devbus,rd-hold-ps:   Defines the time between the last data sample to the
                        de-assertion of DEV_CSn. If set to 0 (default),
@@ -62,16 +77,20 @@ Read parameters:
                         last data sampled. Also this parameter has no
                         affect on <turn-off-ps> parameter.
                         Set <rd-hold-ps> to a value smaller than <turn-off-ps>.
+                        Mandatory for "marvell,mvebu-devbus" compatible string,
+                        except if devbus,keep-config is used.
 
 Write parameters:
 
  - devbus,ale-wr-ps:    Defines the time delay from the ALE[0] negation cycle
                        to the DEV_WEn assertion.
+                        Mandatory.
 
  - devbus,wr-low-ps:    Defines the time during which DEV_WEn is active.
                         A[2:0] and Data are kept valid as long as DEV_WEn
                         is active. This parameter defines the setup time of
                         address and data to DEV_WEn rise.
+                        Mandatory.
 
  - devbus,wr-high-ps:   Defines the time during which DEV_WEn is kept
                         inactive (high) between data beats of a burst write.
@@ -79,10 +98,13 @@ Write parameters:
                         <wr-high-ps> - <tick> ps.
                        This parameter defines the hold time of address and
                        data after DEV_WEn rise.
+                        Mandatory.
 
  - devbus,sync-enable: Synchronous device enable.
                        1: True
                        0: False
+                       Mandatory for "marvell,mvebu-devbus" compatible string,
+                       except if devbus,keep-config is used.
 
 An example for an Armada XP GP board, with a 16 MiB NOR device as child
 is showed below. Note that the Device Bus driver is in charge of allocating