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fdt: add support for adding pmem nodes

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One of the problems an OS may face, when running in EFI, is that
a mounted ISO, after calling ExitBootServices goes away, if that ISO
is resident in RAM memory as a ramdisk.

ACPI has NFIT and NVDIMM support to provide ramdisks to the OS, but we
don't have anything in place for DTs. Linux and device trees have support
for persistent memory devices. So add a function that can inject a pmem
node in a DT, so we can pass information on the ramdisk the OS.

Signed-off-by: Masahisa Kojima <kojima.masahisa@socionext.com>
Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
This commit is contained in:
Masahisa Kojima 2025-03-17 14:03:57 +05:30 • committed by Ilias Apalodimas
parent 7e624377e9
commit 9c407347b4
2 changed files with 52 additions and 1 deletions
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39
boot/fdt_support.c
View file

@ -18,6 +18,7 @@
#include <dm/ofnode.h>
#include <linux/ctype.h>
#include <linux/types.h>
#include <linux/sizes.h>
#include <asm/global_data.h>
#include <asm/unaligned.h>
#include <linux/libfdt.h>
@ -464,7 +465,6 @@ void do_fixup_by_compat_u32(void *fdt, const char *compat,
do_fixup_by_compat(fdt, compat, prop, &tmp, 4, create);
}
#ifdef CONFIG_ARCH_FIXUP_FDT_MEMORY
/*
* fdt_pack_reg - pack address and size array into the "reg"-suitable stream
*/
@ -493,6 +493,7 @@ static int fdt_pack_reg(const void *fdt, void *buf, u64 *address, u64 *size,
return p - (char *)buf;
}
#ifdef CONFIG_ARCH_FIXUP_FDT_MEMORY
#if CONFIG_NR_DRAM_BANKS > 4
#define MEMORY_BANKS_MAX CONFIG_NR_DRAM_BANKS
#else
@ -2222,3 +2223,39 @@ int fdt_valid(struct fdt_header **blobp)
}
return 1;
}
int fdt_fixup_pmem_region(void *fdt, u64 pmem_start, u64 pmem_size)
{
char node_name[32];
int nodeoffset, len;
int err;
u8 tmp[4 * 16]; /* Up to 64-bit address + 64-bit size */
if (!IS_ALIGNED(pmem_start, SZ_2M) ||
!IS_ALIGNED(pmem_start + pmem_size, SZ_2M)) {
printf("Start and end address must be 2MiB aligned\n");
return -1;
}
snprintf(node_name, sizeof(node_name), "pmem@%llx", pmem_start);
nodeoffset = fdt_find_or_add_subnode(fdt, 0, node_name);
if (nodeoffset < 0)
return nodeoffset;
err = fdt_setprop_string(fdt, nodeoffset, "compatible", "pmem-region");
if (err)
return err;
err = fdt_setprop_empty(fdt, nodeoffset, "volatile");
if (err)
return err;
len = fdt_pack_reg(fdt, tmp, &pmem_start, &pmem_size, 1);
err = fdt_setprop(fdt, nodeoffset, "reg", tmp, len);
if (err < 0) {
printf("WARNING: could not set pmem %s %s.\n", "reg",
fdt_strerror(err));
return err;
}
return 0;
}

14
include/fdt_support.h
View file

@ -471,6 +471,20 @@ int fdt_valid(struct fdt_header **blobp);
*/
int fdt_get_cells_len(const void *blob, char *nr_cells_name);
/**
* fdt_fixup_pmem_region() - add a pmem node on the device tree
*
* This functions adds/updates a pmem node to the device tree.
* Usually used with EFI installers to preserve installer
* images
*
* @fdt: device tree provided by caller
* @addr: start address of the pmem node
* @size: size of the memory of the pmem node
* Return: 0 on success or < 0 on failure
*/
int fdt_fixup_pmem_region(void *fdt, u64 pmem_start, u64 pmem_size);
#endif /* !USE_HOSTCC */
#ifdef USE_HOSTCC