efi/arm: Move FDT param discovery code out of efi.c

On ARM systems, we discover the UEFI system table address and memory
map address from the /chosen node in the device tree, or in the Xen
case, from a similar node under /hypervisor.

Before making some functional changes to that code, move it into its
own file that only gets built if CONFIG_EFI_PARAMS_FROM_FDT=y.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

1 files changed, 142 insertions, 0 deletions

diff --git a/drivers/firmware/efi/fdtparams.c b/drivers/firmware/efi/fdtparams.c
new file mode 100644
index 000000000000..3de343faffc6
--- /dev/null
+++ b/drivers/firmware/efi/fdtparams.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#define pr_fmt(fmt) "efi: " fmt
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/efi.h>
+#include <linux/of.h>
+#include <linux/of_fdt.h>
+
+#include <asm/early_ioremap.h>
+
+#define UEFI_PARAM(name, prop, field)			   \
+	{						   \
+		{ name },				   \
+		{ prop },				   \
+		offsetof(struct efi_fdt_params, field),    \
+		sizeof_field(struct efi_fdt_params, field) \
+	}
+
+struct params {
+	const char name[32];
+	const char propname[32];
+	int offset;
+	int size;
+};
+
+static __initdata struct params fdt_params[] = {
+	UEFI_PARAM("System Table", "linux,uefi-system-table", system_table),
+	UEFI_PARAM("MemMap Address", "linux,uefi-mmap-start", mmap),
+	UEFI_PARAM("MemMap Size", "linux,uefi-mmap-size", mmap_size),
+	UEFI_PARAM("MemMap Desc. Size", "linux,uefi-mmap-desc-size", desc_size),
+	UEFI_PARAM("MemMap Desc. Version", "linux,uefi-mmap-desc-ver", desc_ver)
+};
+
+static __initdata struct params xen_fdt_params[] = {
+	UEFI_PARAM("System Table", "xen,uefi-system-table", system_table),
+	UEFI_PARAM("MemMap Address", "xen,uefi-mmap-start", mmap),
+	UEFI_PARAM("MemMap Size", "xen,uefi-mmap-size", mmap_size),
+	UEFI_PARAM("MemMap Desc. Size", "xen,uefi-mmap-desc-size", desc_size),
+	UEFI_PARAM("MemMap Desc. Version", "xen,uefi-mmap-desc-ver", desc_ver)
+};
+
+#define EFI_FDT_PARAMS_SIZE	ARRAY_SIZE(fdt_params)
+
+static __initdata struct {
+	const char *uname;
+	const char *subnode;
+	struct params *params;
+} dt_params[] = {
+	{ "hypervisor", "uefi", xen_fdt_params },
+	{ "chosen", NULL, fdt_params },
+};
+
+struct param_info {
+	int found;
+	void *params;
+	const char *missing;
+};
+
+static int __init __find_uefi_params(unsigned long node,
+				     struct param_info *info,
+				     struct params *params)
+{
+	const void *prop;
+	void *dest;
+	u64 val;
+	int i, len;
+
+	for (i = 0; i < EFI_FDT_PARAMS_SIZE; i++) {
+		prop = of_get_flat_dt_prop(node, params[i].propname, &len);
+		if (!prop) {
+			info->missing = params[i].name;
+			return 0;
+		}
+
+		dest = info->params + params[i].offset;
+		info->found++;
+
+		val = of_read_number(prop, len / sizeof(u32));
+
+		if (params[i].size == sizeof(u32))
+			*(u32 *)dest = val;
+		else
+			*(u64 *)dest = val;
+
+		if (efi_enabled(EFI_DBG))
+			pr_info("  %s: 0x%0*llx\n", params[i].name,
+				params[i].size * 2, val);
+	}
+
+	return 1;
+}
+
+static int __init fdt_find_uefi_params(unsigned long node, const char *uname,
+				       int depth, void *data)
+{
+	struct param_info *info = data;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(dt_params); i++) {
+		const char *subnode = dt_params[i].subnode;
+
+		if (depth != 1 || strcmp(uname, dt_params[i].uname) != 0) {
+			info->missing = dt_params[i].params[0].name;
+			continue;
+		}
+
+		if (subnode) {
+			int err = of_get_flat_dt_subnode_by_name(node, subnode);
+
+			if (err < 0)
+				return 0;
+
+			node = err;
+		}
+
+		return __find_uefi_params(node, info, dt_params[i].params);
+	}
+
+	return 0;
+}
+
+int __init efi_get_fdt_params(struct efi_fdt_params *params)
+{
+	struct param_info info;
+	int ret;
+
+	pr_info("Getting EFI parameters from FDT:\n");
+
+	info.found = 0;
+	info.params = params;
+
+	ret = of_scan_flat_dt(fdt_find_uefi_params, &info);
+	if (!info.found)
+		pr_info("UEFI not found.\n");
+	else if (!ret)
+		pr_err("Can't find '%s' in device tree!\n",
+		       info.missing);
+
+	return ret;
+}