1 CE4100 I2C
2 ----------
3
4 CE4100 has one PCI device which is described as the I2C-Controller. This
5 PCI device has three PCI-bars, each bar contains a complete I2C
6 controller. So we have a total of three independent I2C-Controllers
7 which share only an interrupt line.
8 The driver is probed via the PCI-ID and is gathering the information of
9 attached devices from the devices tree.
10 Grant Likely recommended to use the ranges property to map the PCI-Bar
11 number to its physical address and to use this to find the child nodes
12 of the specific I2C controller. This were his exact words:
13
14 Here's where the magic happens. Each entry in
15 ranges describes how the parent pci address space
16 (middle group of 3) is translated to the local
17 address space (first group of 2) and the size of
18 each range (last cell). In this particular case,
19 the first cell of the local address is chosen to be
20 1:1 mapped to the BARs, and the second is the
21 offset from be base of the BAR (which would be
22 non-zero if you had 2 or more devices mapped off
23 the same BAR)
24
25 ranges allows the address mapping to be described
26 in a way that the OS can interpret without
27 requiring custom device driver code.
28
29 This is an example which is used on FalconFalls:
30 ------------------------------------------------
31 i2c-controller@b,2 {
32 #address-cells = <2>;
33 #size-cells = <1>;
34 compatible = "pci8086,2e68.2",
35 "pci8086,2e68",
36 "pciclass,ff0000",
37 "pciclass,ff00";
38
39 reg = <0x15a00 0x0 0x0 0x0 0x0>;
40 interrupts = <16 1>;
41
42 /* as described by Grant, the first number in the group of
43 * three is the bar number followed by the 64bit bar address
44 * followed by size of the mapping. The bar address
45 * requires also a valid translation in parents ranges
46 * property.
47 */
48 ranges = <0 0 0x02000000 0 0xdffe0500 0x100
49 1 0 0x02000000 0 0xdffe0600 0x100
50 2 0 0x02000000 0 0xdffe0700 0x100>;
51
52 i2c@0 {
53 #address-cells = <1>;
54 #size-cells = <0>;
55 compatible = "intel,ce4100-i2c-controller";
56
57 /* The first number in the reg property is the
58 * number of the bar
59 */
60 reg = <0 0 0x100>;
61
62 /* This I2C controller has no devices */
63 };
64
65 i2c@1 {
66 #address-cells = <1>;
67 #size-cells = <0>;
68 compatible = "intel,ce4100-i2c-controller";
69 reg = <1 0 0x100>;
70
71 /* This I2C controller has one gpio controller */
72 gpio@26 {
73 #gpio-cells = <2>;
74 compatible = "nxp,pcf8575";
75 reg = <0x26>;
76 gpio-controller;
77 };
78 };
79
80 i2c@2 {
81 #address-cells = <1>;
82 #size-cells = <0>;
83 compatible = "intel,ce4100-i2c-controller";
84 reg = <2 0 0x100>;
85
86 gpio@26 {
87 #gpio-cells = <2>;
88 compatible = "nxp,pcf8575";
89 reg = <0x26>;
90 gpio-controller;
91 };
92 };
93 };
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