| Kyle Swenson | 8d8f654 | 2021-03-15 11:02:55 -0600 | [diff] [blame^] | 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 = "ti,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 = "ti,pcf8575"; |
| 89 | reg = <0x26>; |
| 90 | gpio-controller; |
| 91 | }; |
| 92 | }; |
| 93 | }; |