xref: /linux/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt (revision ca55b2fef3a9373fcfc30f82fd26bc7fccbda732)
1Device tree bindings for MVEBU Device Bus controllers
2
3The Device Bus controller available in some Marvell's SoC allows to control
4different types of standard memory and I/O devices such as NOR, NAND, and FPGA.
5The actual devices are instantiated from the child nodes of a Device Bus node.
6
7Required properties:
8
9 - compatible:          Armada 370/XP SoC are supported using the
10                        "marvell,mvebu-devbus" compatible string.
11
12                        Orion5x SoC are supported using the
13                        "marvell,orion-devbus" compatible string.
14
15 - reg:                 A resource specifier for the register space.
16                        This is the base address of a chip select within
17			the controller's register space.
18                        (see the example below)
19
20 - #address-cells:      Must be set to 1
21 - #size-cells:         Must be set to 1
22 - ranges:              Must be set up to reflect the memory layout with four
23                        integer values for each chip-select line in use:
24                        0 <physical address of mapping> <size>
25
26Optional properties:
27
28 - devbus,keep-config   This property can optionally be used to keep
29                        using the timing parameters set by the
30                        bootloader. It makes all the timing properties
31                        described below unused.
32
33Timing properties for child nodes:
34
35Read parameters:
36
37 - devbus,turn-off-ps:  Defines the time during which the controller does not
38                        drive the AD bus after the completion of a device read.
39                        This prevents contentions on the Device Bus after a read
40                        cycle from a slow device.
41                        Mandatory, except if devbus,keep-config is used.
42
43 - devbus,bus-width:    Defines the bus width, in bits (e.g. <16>).
44                        Mandatory, except if devbus,keep-config is used.
45
46 - devbus,badr-skew-ps: Defines the time delay from from A[2:0] toggle,
47                        to read data sample. This parameter is useful for
48                        synchronous pipelined devices, where the address
49                        precedes the read data by one or two cycles.
50                        Mandatory, except if devbus,keep-config is used.
51
52 - devbus,acc-first-ps: Defines the time delay from the negation of
53                        ALE[0] to the cycle that the first read data is sampled
54                        by the controller.
55                        Mandatory, except if devbus,keep-config is used.
56
57 - devbus,acc-next-ps:  Defines the time delay between the cycle that
58                        samples data N and the cycle that samples data N+1
59                        (in burst accesses).
60                        Mandatory, except if devbus,keep-config is used.
61
62 - devbus,rd-setup-ps:  Defines the time delay between DEV_CSn assertion to
63			DEV_OEn assertion. If set to 0 (default),
64                        DEV_OEn and DEV_CSn are asserted at the same cycle.
65                        This parameter has no affect on <acc-first-ps> parameter
66                        (no affect on first data sample). Set <rd-setup-ps>
67                        to a value smaller than <acc-first-ps>.
68                        Mandatory for "marvell,mvebu-devbus" compatible string,
69                        except if devbus,keep-config is used.
70
71 - devbus,rd-hold-ps:   Defines the time between the last data sample to the
72			de-assertion of DEV_CSn. If set to 0 (default),
73			DEV_OEn and DEV_CSn are de-asserted at the same cycle
74			(the cycle of the last data sample).
75                        This parameter has no affect on DEV_OEn de-assertion.
76                        DEV_OEn is always de-asserted the next cycle after
77                        last data sampled. Also this parameter has no
78                        affect on <turn-off-ps> parameter.
79                        Set <rd-hold-ps> to a value smaller than <turn-off-ps>.
80                        Mandatory for "marvell,mvebu-devbus" compatible string,
81                        except if devbus,keep-config is used.
82
83Write parameters:
84
85 - devbus,ale-wr-ps:    Defines the time delay from the ALE[0] negation cycle
86			to the DEV_WEn assertion.
87                        Mandatory.
88
89 - devbus,wr-low-ps:    Defines the time during which DEV_WEn is active.
90                        A[2:0] and Data are kept valid as long as DEV_WEn
91                        is active. This parameter defines the setup time of
92                        address and data to DEV_WEn rise.
93                        Mandatory.
94
95 - devbus,wr-high-ps:   Defines the time during which DEV_WEn is kept
96                        inactive (high) between data beats of a burst write.
97                        DEV_A[2:0] and Data are kept valid (do not toggle) for
98                        <wr-high-ps> - <tick> ps.
99			This parameter defines the hold time of address and
100			data after DEV_WEn rise.
101                        Mandatory.
102
103 - devbus,sync-enable: Synchronous device enable.
104                       1: True
105                       0: False
106                       Mandatory for "marvell,mvebu-devbus" compatible string,
107                       except if devbus,keep-config is used.
108
109An example for an Armada XP GP board, with a 16 MiB NOR device as child
110is showed below. Note that the Device Bus driver is in charge of allocating
111the mbus address decoding window for each of its child devices.
112The window is created using the chip select specified in the child
113device node together with the base address and size specified in the ranges
114property. For instance, in the example below the allocated decoding window
115will start at base address 0xf0000000, with a size 0x1000000 (16 MiB)
116for chip select 0 (a.k.a DEV_BOOTCS).
117
118This address window handling is done in this mvebu-devbus only as a temporary
119solution. It will be removed when the support for mbus device tree binding is
120added.
121
122The reg property implicitly specifies the chip select as this:
123
124  0x10400: DEV_BOOTCS
125  0x10408: DEV_CS0
126  0x10410: DEV_CS1
127  0x10418: DEV_CS2
128  0x10420: DEV_CS3
129
130Example:
131
132	devbus-bootcs@d0010400 {
133		status = "okay";
134		ranges = <0 0xf0000000 0x1000000>; /* @addr 0xf0000000, size 0x1000000 */
135		#address-cells = <1>;
136		#size-cells = <1>;
137
138		/* Device Bus parameters are required */
139
140		/* Read parameters */
141		devbus,bus-width    = <8>;
142		devbus,turn-off-ps  = <60000>;
143		devbus,badr-skew-ps = <0>;
144		devbus,acc-first-ps = <124000>;
145		devbus,acc-next-ps  = <248000>;
146		devbus,rd-setup-ps  = <0>;
147		devbus,rd-hold-ps   = <0>;
148
149		/* Write parameters */
150		devbus,sync-enable = <0>;
151		devbus,wr-high-ps  = <60000>;
152		devbus,wr-low-ps   = <60000>;
153		devbus,ale-wr-ps   = <60000>;
154
155		flash@0 {
156			compatible = "cfi-flash";
157
158			/* 16 MiB */
159			reg = <0 0x1000000>;
160			bank-width = <2>;
161			#address-cells = <1>;
162			#size-cells = <1>;
163
164			/*
165			 * We split the 16 MiB in two partitions,
166			 * just as an example.
167			 */
168			partition@0 {
169				label = "First";
170				reg = <0 0x800000>;
171			};
172
173			partition@800000 {
174				label = "Second";
175				reg = <0x800000 0x800000>;
176			};
177		};
178	};
179