summaryrefslogtreecommitdiff
path: root/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt')
-rw-r--r--Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt156
1 files changed, 156 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt b/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
new file mode 100644
index 000000000000..653c90c34a71
--- /dev/null
+++ b/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
@@ -0,0 +1,156 @@
+Device tree bindings for MVEBU Device Bus controllers
+
+The Device Bus controller available in some Marvell's SoC allows to control
+different types of standard memory and I/O devices such as NOR, NAND, and FPGA.
+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:
+
+ marvell,mvebu-devbus
+
+ - reg: A resource specifier for the register space.
+ This is the base address of a chip select within
+ the controller's register space.
+ (see the example below)
+
+ - #address-cells: Must be set to 1
+ - #size-cells: Must be set to 1
+ - ranges: Must be set up to reflect the memory layout with four
+ integer values for each chip-select line in use:
+ 0 <physical address of mapping> <size>
+
+Mandatory timing properties for child nodes:
+
+Read parameters:
+
+ - devbus,turn-off-ps: Defines the time during which the controller does not
+ 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.
+
+ - devbus,bus-width: Defines the bus width (e.g. <16>)
+
+ - 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.
+
+ - 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.
+
+ - 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).
+
+ - devbus,rd-setup-ps: Defines the time delay between DEV_CSn assertion to
+ DEV_OEn assertion. If set to 0 (default),
+ DEV_OEn and DEV_CSn are asserted at the same cycle.
+ 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>.
+
+ - devbus,rd-hold-ps: Defines the time between the last data sample to the
+ de-assertion of DEV_CSn. If set to 0 (default),
+ DEV_OEn and DEV_CSn are de-asserted at the same cycle
+ (the cycle of the last data sample).
+ This parameter has no affect on DEV_OEn de-assertion.
+ DEV_OEn is always de-asserted the next cycle after
+ 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>.
+
+Write parameters:
+
+ - devbus,ale-wr-ps: Defines the time delay from the ALE[0] negation cycle
+ to the DEV_WEn assertion.
+
+ - 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.
+
+ - devbus,wr-high-ps: Defines the time during which DEV_WEn is kept
+ inactive (high) between data beats of a burst write.
+ DEV_A[2:0] and Data are kept valid (do not toggle) for
+ <wr-high-ps> - <tick> ps.
+ This parameter defines the hold time of address and
+ data after DEV_WEn rise.
+
+ - devbus,sync-enable: Synchronous device enable.
+ 1: True
+ 0: False
+
+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
+the mbus address decoding window for each of its child devices.
+The window is created using the chip select specified in the child
+device node together with the base address and size specified in the ranges
+property. For instance, in the example below the allocated decoding window
+will start at base address 0xf0000000, with a size 0x1000000 (16 MiB)
+for chip select 0 (a.k.a DEV_BOOTCS).
+
+This address window handling is done in this mvebu-devbus only as a temporary
+solution. It will be removed when the support for mbus device tree binding is
+added.
+
+The reg property implicitly specifies the chip select as this:
+
+ 0x10400: DEV_BOOTCS
+ 0x10408: DEV_CS0
+ 0x10410: DEV_CS1
+ 0x10418: DEV_CS2
+ 0x10420: DEV_CS3
+
+Example:
+
+ devbus-bootcs@d0010400 {
+ status = "okay";
+ ranges = <0 0xf0000000 0x1000000>; /* @addr 0xf0000000, size 0x1000000 */
+ #address-cells = <1>;
+ #size-cells = <1>;
+
+ /* Device Bus parameters are required */
+
+ /* Read parameters */
+ devbus,bus-width = <8>;
+ devbus,turn-off-ps = <60000>;
+ devbus,badr-skew-ps = <0>;
+ devbus,acc-first-ps = <124000>;
+ devbus,acc-next-ps = <248000>;
+ devbus,rd-setup-ps = <0>;
+ devbus,rd-hold-ps = <0>;
+
+ /* Write parameters */
+ devbus,sync-enable = <0>;
+ devbus,wr-high-ps = <60000>;
+ devbus,wr-low-ps = <60000>;
+ devbus,ale-wr-ps = <60000>;
+
+ flash@0 {
+ compatible = "cfi-flash";
+
+ /* 16 MiB */
+ reg = <0 0x1000000>;
+ bank-width = <2>;
+ #address-cells = <1>;
+ #size-cells = <1>;
+
+ /*
+ * We split the 16 MiB in two partitions,
+ * just as an example.
+ */
+ partition@0 {
+ label = "First";
+ reg = <0 0x800000>;
+ };
+
+ partition@800000 {
+ label = "Second";
+ reg = <0x800000 0x800000>;
+ };
+ };
+ };