summaryrefslogtreecommitdiff
path: root/Documentation/devicetree/bindings/memory-controllers
diff options
context:
space:
mode:
authorThomas Petazzoni <thomas.petazzoni@free-electrons.com>2014-04-22 23:26:13 +0200
committerJason Cooper <jason@lakedaemon.net>2014-04-29 13:17:10 +0000
commit0456d3300edba52e47c6b5582cfe9d87756f5590 (patch)
tree1ee7546cebd4f327e73d7e9c48332692b3402573 /Documentation/devicetree/bindings/memory-controllers
parentc4ec7430c30a4012a04aa5535919845f543f075d (diff)
memory: mvebu-devbus: add a devbus, keep-config property
Currently, the mvebu-devbus Device Tree binding makes defining the timing parameters mandatory. However, in practice, when converting Orion5x platforms to the Device Tree, we may not necessarily have easy access to the hardware platforms to fetch those values which were not defined in old-style board files: all these platforms rely on the bootloader setting the timing parameters correctly. In order to facilitate the migration to the Device Tree of this platform, this commit relaxes the mvebu-devbus Device Tree binding by introducing a 'devbus,keep-config' boolean property, which, if defined, will ignore all timing parameters passed in the Device Tree, and simply rely on the timing values already defined by the bootloader. Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com> Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com> Link: https://lkml.kernel.org/r/1398202002-28530-10-git-send-email-thomas.petazzoni@free-electrons.com Signed-off-by: Jason Cooper <jason@lakedaemon.net>
Diffstat (limited to 'Documentation/devicetree/bindings/memory-controllers')
-rw-r--r--Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt29
1 files changed, 18 insertions, 11 deletions
diff --git a/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt b/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
index 55adde214627..1ee3bc09f319 100644
--- a/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
+++ b/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
@@ -23,6 +23,13 @@ Required properties:
integer values for each chip-select line in use:
0 <physical address of mapping> <size>
+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:
@@ -31,26 +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.
+ Mandatory, except if devbus,keep-config is used.
- devbus,bus-width: Defines the bus width, in bits (e.g. <16>).
- Mandatory.
+ 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.
+ 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.
+ 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.
+ 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),
@@ -58,8 +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, ignored otherwise.
+ 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),
@@ -70,8 +77,8 @@ 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, ignored otherwise.
+ Mandatory for "marvell,mvebu-devbus" compatible string,
+ except if devbus,keep-config is used.
Write parameters:
@@ -96,8 +103,8 @@ Write parameters:
- devbus,sync-enable: Synchronous device enable.
1: True
0: False
- Mandatory for "marvell,mvebu-devbus" compatible
- string, ignored otherwise.
+ 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