| Tom Rini | 53633a8 | 2024-02-29 12:33:36 -0500 | [diff] [blame] | 1 | Device-tree bindings for persistent memory regions |
| 2 | ----------------------------------------------------- |
| 3 | |
| 4 | Persistent memory refers to a class of memory devices that are: |
| 5 | |
| 6 | a) Usable as main system memory (i.e. cacheable), and |
| 7 | b) Retain their contents across power failure. |
| 8 | |
| 9 | Given b) it is best to think of persistent memory as a kind of memory mapped |
| 10 | storage device. To ensure data integrity the operating system needs to manage |
| 11 | persistent regions separately to the normal memory pool. To aid with that this |
| 12 | binding provides a standardised interface for discovering where persistent |
| 13 | memory regions exist inside the physical address space. |
| 14 | |
| 15 | Bindings for the region nodes: |
| 16 | ----------------------------- |
| 17 | |
| 18 | Required properties: |
| 19 | - compatible = "pmem-region" |
| 20 | |
| 21 | - reg = <base, size>; |
| 22 | The reg property should specify an address range that is |
| 23 | translatable to a system physical address range. This address |
| 24 | range should be mappable as normal system memory would be |
| 25 | (i.e cacheable). |
| 26 | |
| 27 | If the reg property contains multiple address ranges |
| 28 | each address range will be treated as though it was specified |
| 29 | in a separate device node. Having multiple address ranges in a |
| 30 | node implies no special relationship between the two ranges. |
| 31 | |
| 32 | Optional properties: |
| 33 | - Any relevant NUMA associativity properties for the target platform. |
| 34 | |
| 35 | - volatile; This property indicates that this region is actually |
| 36 | backed by non-persistent memory. This lets the OS know that it |
| 37 | may skip the cache flushes required to ensure data is made |
| 38 | persistent after a write. |
| 39 | |
| 40 | If this property is absent then the OS must assume that the region |
| 41 | is backed by non-volatile memory. |
| 42 | |
| 43 | Examples: |
| 44 | -------------------- |
| 45 | |
| 46 | /* |
| 47 | * This node specifies one 4KB region spanning from |
| 48 | * 0x5000 to 0x5fff that is backed by non-volatile memory. |
| 49 | */ |
| 50 | pmem@5000 { |
| 51 | compatible = "pmem-region"; |
| 52 | reg = <0x00005000 0x00001000>; |
| 53 | }; |
| 54 | |
| 55 | /* |
| 56 | * This node specifies two 4KB regions that are backed by |
| 57 | * volatile (normal) memory. |
| 58 | */ |
| 59 | pmem@6000 { |
| 60 | compatible = "pmem-region"; |
| 61 | reg = < 0x00006000 0x00001000 |
| 62 | 0x00008000 0x00001000 >; |
| 63 | volatile; |
| 64 | }; |
| 65 | |