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-rw-r--r--Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt32
1 files changed, 27 insertions, 5 deletions
diff --git a/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt b/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
index 653c90c..1ee3bc0 100644
--- 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
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