85 lines
3.0 KiB
ReStructuredText
85 lines
3.0 KiB
ReStructuredText
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.. _memory_management_shared_multi_heap:
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Shared Multi Heap
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#################
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The shared multi-heap memory pool manager uses the multi-heap allocator to
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manage a set of reserved memory regions with different capabilities /
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attributes (cacheable, non-cacheable, etc...) defined in the DT.
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The user can request allocation from the shared pool specifying the capability
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/ attribute of interest for the memory (cacheable / non-cacheable memory,
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etc...).
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The different heaps with their attributes available in the shared pool are
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defined into the DT file leveraging the ``reserved-memory`` nodes.
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This is a DT example declaring three different memory regions with different
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cacheability attributes: ``cacheable`` and ``non-cacheable``
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.. code-block:: devicetree
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/ {
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reserved-memory {
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compatible = "reserved-memory";
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#address-cells = <1>;
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#size-cells = <1>;
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res0: reserved@42000000 {
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compatible = "shared-multi-heap";
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reg = <0x42000000 0x1000>;
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capability = "cacheable";
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label = "res0";
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};
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res1: reserved@43000000 {
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compatible = "shared-multi-heap";
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reg = <0x43000000 0x2000>;
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capability = "non-cacheable";
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label = "res1";
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};
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res2: reserved2@44000000 {
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compatible = "shared-multi-heap";
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reg = <0x44000000 0x3000>;
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capability = "cacheable";
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label = "res2";
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};
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};
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The user can then request 4K from heap memory ``cacheable`` or
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``non-cacheable`` using the provided APIs:
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.. code-block:: c
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// Allocate 4K from cacheable memory
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shared_multi_heap_alloc(SMH_REG_ATTR_CACHEABLE, 0x1000);
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// Allocate 4K from non-cacheable
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shared_multi_heap_alloc(SMH_REG_ATTR_NON_CACHEABLE, 0x1000);
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The backend implementation will allocate the memory region from the heap with
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the correct attribute and using the region able to accommodate the required size.
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Special handling for MMU/MPU
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****************************
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For MMU/MPU enabled platform sometimes it is required to setup and configure
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the memory regions before these are added to the managed pool. This is done at
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init time using the :c:func:`shared_multi_heap_pool_init()` function that is
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accepting a :c:type:`smh_init_reg_fn_t` callback function. This callback will
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be called for each memory region at init time and it can be used to correctly
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map the region before this is considered valid and accessible.
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Adding new attributes
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*********************
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Currently only two memory attributes are supported: ``cacheable`` and
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``non-cacheable``. To add a new attribute:
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1. Add the new ``enum`` for the attribute in the :c:enum:`smh_reg_attr`
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2. Add the corresponding attribute name in :file:`shared-multi-heap.yaml`
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.. doxygengroup:: shared_multi_heap
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:project: Zephyr
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