option: Allow to use the EFI variable driver as option backend

Use the introduced EFI variable store driver on top of the SMMSTORE
region in SPI flash to read/write options.

Change-Id: I520eca96bcd573f825ed35a29bf8f750e313a02d
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62562
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/Kconfig

@@ -142,6 +142,8 @@ choice
 	prompt "Option backend to use"
 	default USE_MAINBOARD_SPECIFIC_OPTION_BACKEND if HAVE_MAINBOARD_SPECIFIC_OPTION_BACKEND
 	default USE_OPTION_TABLE if NVRAMCUI_SECONDARY_PAYLOAD
+	default USE_UEFI_VARIABLE_STORE if DRIVERS_EFI_VARIABLE_STORE && \
+		PAYLOAD_EDK2 && SMMSTORE_V2
 
 config OPTION_BACKEND_NONE
 	bool "None"
@@ -153,6 +155,15 @@ config USE_OPTION_TABLE
 	  Enable this option if coreboot shall read options from the "CMOS"
 	  NVRAM instead of using hard-coded values.
 
+config USE_UEFI_VARIABLE_STORE
+	bool "Use UEFI variable-store in SPI flash as option backend"
+	depends on DRIVERS_EFI_VARIABLE_STORE
+	depends on SMMSTORE_V2
+	help
+	  Enable this option if coreboot shall read/write options from the
+	  SMMSTORE region within the SPI flash. The region must be formatted
+	  by the payload first before it can be used.
+
 config USE_MAINBOARD_SPECIFIC_OPTION_BACKEND
 	bool "Use mainboard-specific option backend"
 	depends on HAVE_MAINBOARD_SPECIFIC_OPTION_BACKEND

src/drivers/efi/option.c

@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <stdlib.h>
+#include <string.h>
+#include <option.h>
+#include <smmstore.h>
+
+#include <Uefi/UefiBaseType.h>
+
+#include "efivars.h"
+
+static const EFI_GUID EficorebootNvDataGuid = {
+	0xceae4c1d, 0x335b, 0x4685, { 0xa4, 0xa0, 0xfc, 0x4a, 0x94, 0xee, 0xa0, 0x85 } };
+
+unsigned int get_uint_option(const char *name, const unsigned int fallback)
+{
+	struct region_device rdev;
+	enum cb_err ret;
+	uint32_t var;
+	uint32_t size;
+
+	if (smmstore_lookup_region(&rdev))
+		return fallback;
+
+	var = 0;
+	size = sizeof(var);
+	ret = efi_fv_get_option(&rdev, &EficorebootNvDataGuid, name, &var, &size);
+	if (ret != CB_SUCCESS)
+		return fallback;
+
+	return var;
+}
+
+enum cb_err set_uint_option(const char *name, unsigned int value)
+{
+	struct region_device rdev;
+	uint32_t var = value;
+
+	if (smmstore_lookup_region(&rdev))
+		return CB_CMOS_OTABLE_DISABLED;
+
+	return efi_fv_set_option(&rdev, &EficorebootNvDataGuid, name, &var, sizeof(var));
+}