66 lines
2.1 KiB
Plaintext
66 lines
2.1 KiB
Plaintext
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Device-tree bindings for persistent memory regions
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-----------------------------------------------------
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Persistent memory refers to a class of memory devices that are:
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a) Usable as main system memory (i.e. cacheable), and
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b) Retain their contents across power failure.
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Given b) it is best to think of persistent memory as a kind of memory mapped
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storage device. To ensure data integrity the operating system needs to manage
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persistent regions separately to the normal memory pool. To aid with that this
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binding provides a standardised interface for discovering where persistent
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memory regions exist inside the physical address space.
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Bindings for the region nodes:
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-----------------------------
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Required properties:
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- compatible = "pmem-region"
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- reg = <base, size>;
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The reg property should specificy an address range that is
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translatable to a system physical address range. This address
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range should be mappable as normal system memory would be
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(i.e cacheable).
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If the reg property contains multiple address ranges
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each address range will be treated as though it was specified
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in a separate device node. Having multiple address ranges in a
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node implies no special relationship between the two ranges.
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Optional properties:
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- Any relevant NUMA assocativity properties for the target platform.
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- volatile; This property indicates that this region is actually
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backed by non-persistent memory. This lets the OS know that it
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may skip the cache flushes required to ensure data is made
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persistent after a write.
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If this property is absent then the OS must assume that the region
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is backed by non-volatile memory.
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Examples:
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--------------------
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/*
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* This node specifies one 4KB region spanning from
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* 0x5000 to 0x5fff that is backed by non-volatile memory.
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*/
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pmem@5000 {
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compatible = "pmem-region";
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reg = <0x00005000 0x00001000>;
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};
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/*
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* This node specifies two 4KB regions that are backed by
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* volatile (normal) memory.
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*/
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pmem@6000 {
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compatible = "pmem-region";
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reg = < 0x00006000 0x00001000
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0x00008000 0x00001000 >;
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volatile;
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};
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