Add a Memory Mapping in Linux Kernel and ATF
Notes of kernel hacking.
Modifications on Kernel Side
DTS:
...
reserved-memory {
#address-cells = <2>;
#size-cells = <2>;
ranges;
...
memorypool@40000000 {
compatible = "memory-pool";
reusable;
reg = <0x0 0x40000000 0x0 0x00400000>;
};
};
...
kernel/dma/contiguous.c:
...
RESERVEDMEM_OF_DECLARE(cma_shadow, "memory-pool", rmem_cma_setup);
Allocation from the cma memory pool:
struct page *cma_pages;
cma_pages = dma_alloc_from_contiguous(NULL, (NUM_SHADOW_MMIO * SHADOW_MMIO_SIZE) >> PAGE_SHIFT, 0, false);
if (!cma_pages) {
printk(KERN_ERR "Failed to allocate memory for mmio region\n");
return;
}
printk("cma_pages.addr: 0x%lx\n", (unsigned long)page_to_phys(cma_pages));
Modifications on ATF Side
Add a static memory mapping:
#define MEMPOOL_MEM MAP_REGION_FLAT(MEMPOOL_BASE, \
MEMPOOL_SIZE, \
MT_MEMORY | MT_RW | MT_NS)
#ifdef IMAGE_BL31
const mmap_region_t bl_regions[] = {
...
MEMPOOL_MEM,
{0}
};
#endif