linux kernel内存管理学习篇

1、DDR的注册

(1)、在dts中定义了DDR(memory)的范围

memory@0 {device_type = "memory";reg = <0x0 0x80000000 0x2 0x0>;
};

(2)、将DDR地址范围注册到linux kernel

early_init_dt_scan_memory()
early_init_dt_scan_memory() —> early_init_dt_add_memory_arch(base, size) —> memblock_add(base, size)—>memblock_add_region(base, size, MAX_NUMNODES, 0)

(driver/of/fdt.c)
/*** early_init_dt_scan_memory - Look for an parse memory nodes*/
int __init early_init_dt_scan_memory(unsigned long node, const char *uname,int depth, void *data)
{const char *type = of_get_flat_dt_prop(node, "device_type", NULL);const __be32 *reg, *endp;int l;/* We are scanning "memory" nodes only */if (type == NULL) {/** The longtrail doesn't have a device_type on the* /memory node, so look for the node called /memory@0.*/if (!IS_ENABLED(CONFIG_PPC32) || depth != 1 || strcmp(uname, "memory@0") != 0)return 0;} else if (strcmp(type, "memory") != 0)return 0;reg = of_get_flat_dt_prop(node, "linux,usable-memory", &l);if (reg == NULL)reg = of_get_flat_dt_prop(node, "reg", &l);if (reg == NULL)return 0;endp = reg + (l / sizeof(__be32));pr_debug("memory scan node %s, reg size %d,\n", uname, l);while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) {u64 base, size;base = dt_mem_next_cell(dt_root_addr_cells, &reg);size = dt_mem_next_cell(dt_root_size_cells, &reg);if (size == 0)continue;pr_debug(" - %llx ,  %llx\n", (unsigned long long)base,(unsigned long long)size);early_init_dt_add_memory_arch(base, size);}return 0;
}

MAX_NUMNODES表示有几块DDR区域(注意是几块DDR区域，并不是几块DDR)，大小为1(1<<0)或和CONFIG_NODES_SHIFT值相关

#define MAX_NUMNODES    (1 << NODES_SHIFT)#ifdef CONFIG_NODES_SHIFT
#define NODES_SHIFT     CONFIG_NODES_SHIFT
#else
#define NODES_SHIFT     0
#endif

2、reserved-memory的注册

(1)、在dts中定义了reserved-memory的范围

reserved-memory {#address-cells = <1>;#size-cells = <1>;ranges;/* global autoconfigured region for contiguous allocations */linux,cma {compatible = "shared-dma-pool";reusable;size = <0x4000000>;alignment = <0x2000>;linux,cma-default;};display_reserved: framebuffer@78000000 {reg = <0x78000000 0x800000>;};multimedia_reserved: multimedia@77000000 {compatible = "acme,multimedia-memory";reg = <0x77000000 0x4000000>;};};/* ... */fb0: video@12300000 {memory-region = <&display_reserved>;/* ... */};scaler: scaler@12500000 {memory-region = <&multimedia_reserved>;/* ... */};codec: codec@12600000 {memory-region = <&multimedia_reserved>;/* ... */};

(2)、将reserved memory信息告知给linux kernel

__fdt_scan_reserved_mem()
__fdt_scan_reserved_mem() —> __reserved_mem_reserve_reg() —> early_init_dt_reserve_memory_arch(base, size, nomap)—>memblock_reserve(base, size) —> memblock_reserve_region(base, size, MAX_NUMNODES, 0)

(driver/of/fdt.c)
/*** fdt_scan_reserved_mem() - scan a single FDT node for reserved memory*/
static int __init __fdt_scan_reserved_mem(unsigned long node, const char *uname,int depth, void *data)
{static int found;const char *status;int err;if (!found && depth == 1 && strcmp(uname, "reserved-memory") == 0) {if (__reserved_mem_check_root(node) != 0) {pr_err("Reserved memory: unsupported node format, ignoring\n");/* break scan */return 1;}found = 1;/* scan next node */return 0;} else if (!found) {/* scan next node */return 0;} else if (found && depth < 2) {/* scanning of /reserved-memory has been finished */return 1;}status = of_get_flat_dt_prop(node, "status", NULL);if (status && strcmp(status, "okay") != 0 && strcmp(status, "ok") != 0)return 0;err = __reserved_mem_reserve_reg(node, uname);if (err == -ENOENT && of_get_flat_dt_prop(node, "size", NULL))fdt_reserved_mem_save_node(node, uname, 0, 0);/* scan next node */return 0;
}

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