[PATCH v2 1/4] fdt: add support for adding pmem nodes

[Sughosh Ganu]

From: Masahisa Kojima <kojima.masahisa at socionext.com>

One of the problems OS installers face, when running in EFI, is that
the mounted ISO after calling ExitBootServices goes away. For some
distros this is a problem since they rely on finding some core packages
before continuing the installation. Distros have works around this --
e.g Fedora has a special kernel command line parameter called
inst.stage2 [0].

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 use it when launhing OS installers with EFI.

[0]
https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/7/html/installation_guide/chap-anaconda-boot-options#sect-boot-options-installer

Signed-off-by: Masahisa Kojima <kojima.masahisa at socionext.com>
Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
---
Changes since V1: None

 boot/fdt_support.c    | 41 +++++++++++++++++++++++++++++++++++++++--
 include/fdt_support.h | 13 +++++++++++++
 2 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/boot/fdt_support.c b/boot/fdt_support.c
index 2392027d40b..61f725389b7 100644
--- a/boot/fdt_support.c
+++ b/boot/fdt_support.c
@@ -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>
@@ -463,7 +464,6 @@ 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
  */
@@ -491,7 +491,7 @@ 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
@@ -2221,3 +2221,40 @@ int fdt_valid(struct fdt_header **blobp)
 	}
 	return 1;
 }
+
+int fdt_fixup_pmem_region(void *blob, ulong addr, u32 size)
+{
+	u64 pmem_start[2] = { 0 };
+	u64 pmem_size[2] = { 0 };
+	char pmem_node[32] = {0};
+	int nodeoffset, len;
+	int err;
+	u8 tmp[4 * 16]; /* Up to 64-bit address + 64-bit size */
+
+	if (!IS_ALIGNED(addr, SZ_2M) || !IS_ALIGNED(addr + size, SZ_2M)) {
+		printf("Start and end address needs at 2MB alignment\n");
+		return -1;
+	}
+	snprintf(pmem_node, sizeof(pmem_node), "pmem@%lx", addr);
+	nodeoffset = fdt_find_or_add_subnode(blob, 0, pmem_node);
+	if (nodeoffset < 0)
+		return nodeoffset;
+
+	err = fdt_setprop_string(blob, nodeoffset, "compatible", "pmem-region");
+	if (err)
+		return err;
+	err = fdt_setprop_empty(blob, nodeoffset, "volatile");
+	if (err)
+		return err;
+	pmem_start[0] = addr;
+	pmem_size[0] = size;
+	len = fdt_pack_reg(blob, tmp, pmem_start, pmem_size, 1);
+	err = fdt_setprop(blob, nodeoffset, "reg", tmp, len);
+	if (err < 0) {
+		printf("WARNING: could not set pmem %s %s.\n", "reg",
+		       fdt_strerror(err));
+		return err;
+	}
+
+	return 0;
+}
diff --git a/include/fdt_support.h b/include/fdt_support.h
index 9447a64e060..980feb27d27 100644
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -474,4 +474,17 @@ void fdt_fixup_pstore(void *blob);
  */
 int fdt_kaslrseed(void *blob, bool overwrite);
 
+/**
+ * fdt_fixup_pmem_region() - add a pmem node on the device tree
+ *
+ * This functions injects a pmem node to the device tree. Usually
+ * used with EFI installers to preserve installer images
+ *
+ * @blob:	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 *blob, ulong addr, u32 size);
+
 #endif /* ifndef __FDT_SUPPORT_H */
-- 
2.34.1