[PATCH 8/8] efi/arm: populate screen_info based on data provided by the UEFI stub

[Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

Unlike on arm64, where we can simply access the screen_info struct directly,
ARM requires an intermediate step to get the information discovered by the
GOP code in the UEFI stub into the screen_info struct.

So retrieve the dedicated config table we invented for this purpose, and
put its contents into the core kernel's copy of struct screen_info.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
 arch/arm/kernel/efi.c           | 24 ++++++++++++++++++++
 drivers/firmware/efi/arm-init.c |  6 +++++
 2 files changed, 30 insertions(+)

diff --git a/arch/arm/kernel/efi.c b/arch/arm/kernel/efi.c
index ff8a9d8acfac..8d1119259654 100644
--- a/arch/arm/kernel/efi.c
+++ b/arch/arm/kernel/efi.c
@@ -6,11 +6,35 @@
  * published by the Free Software Foundation.
  */
 
+#define pr_fmt(fmt)     "efi: " fmt
+
 #include <linux/efi.h>
+#include <linux/screen_info.h>
 #include <asm/efi.h>
 #include <asm/mach/map.h>
 #include <asm/mmu_context.h>
 
+static const efi_guid_t __initconst si_tbl = LINUX_ARM32_SCREEN_INFO_TABLE_GUID;
+
+void __init efi_find_screen_info(efi_config_table_t *tbl, u32 num_tables)
+{
+	struct screen_info *si;
+
+	while (num_tables--) {
+		if (efi_guidcmp(tbl->guid, si_tbl) == 0) {
+			si = early_memremap_ro(tbl->table, sizeof(*si));
+			if (!si) {
+				pr_warn("Failed to remap screen_info config table\n");
+				return;
+			}
+			screen_info = *si;
+			early_memunmap(si, sizeof(*si));
+			break;
+		}
+		tbl++;
+	}
+}
+
 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
 {
 	struct map_desc desc = {
diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
index eca9b4f826ee..689bf65f8ddf 100644
--- a/drivers/firmware/efi/arm-init.c
+++ b/drivers/firmware/efi/arm-init.c
@@ -112,6 +112,12 @@ static int __init uefi_init(void)
 	retval = efi_config_parse_tables(config_tables, efi.systab->nr_tables,
 					 sizeof(efi_config_table_t), NULL);
 
+	if (IS_ENABLED(CONFIG_ARM)) {
+		extern void efi_find_screen_info(efi_config_table_t *, u32);
+
+		efi_find_screen_info(config_tables, efi.systab->nr_tables);
+	}
+
 	early_memunmap(config_tables, table_size);
 out:
 	early_memunmap(efi.systab,  sizeof(efi_system_table_t));
-- 
1.9.1