[PATCH v1 2/3] efi_vars: Implement SPI Flash store

[Shantur Rathore <i@shantur.com>]

Currently U-boot uses ESP as storage for EFI variables.
Devices with SPI Flash are used for storing environment with this
commit we allow EFI variables to be stored on SPI Flash.

Signed-off-by: Shantur Rathore <i@shantur.com>
---

 include/efi_variable.h        | 25 ++++++++++
 lib/efi_loader/Kconfig        | 18 +++++++
 lib/efi_loader/Makefile       |  1 +
 lib/efi_loader/efi_var_sf.c   | 91 +++++++++++++++++++++++++++++++++++
 lib/efi_loader/efi_variable.c |  4 ++
 5 files changed, 139 insertions(+)
 create mode 100644 lib/efi_loader/efi_var_sf.c

diff --git a/include/efi_variable.h b/include/efi_variable.h
index ca7e19d514..766dd109f5 100644
--- a/include/efi_variable.h
+++ b/include/efi_variable.h
@@ -188,6 +188,31 @@ efi_status_t efi_var_from_file(void);
 
 #endif // CONFIG_EFI_VARIABLE_FILE_STORE
 
+#ifdef CONFIG_EFI_VARIABLE_SF_STORE
+
+/**
+ * efi_var_from_sf() - read variables from SPI Flash
+ *
+ * EFI variable buffer is read from SPI Flash at offset defined with
+ * CONFIG_EFI_VARIABLE_SF_OFFSET of length CONFIG_EFI_VAR_BUF_SIZE
+ *
+ *
+ * Return:	status code
+ */
+efi_status_t efi_var_from_sf(void);
+
+/**
+ * efi_var_to_sf() - save non-volatile variables to SPI Flash
+ *
+ * EFI variable buffer is saved to SPI Flash at offset defined with
+ * CONFIG_EFI_VARIABLE_SF_OFFSET of length CONFIG_EFI_VAR_BUF_SIZE.
+ *
+ * Return:	status code
+ */
+efi_status_t efi_var_to_sf(void);
+
+#endif // CONFIG_EFI_VARIABLE_SF_STORE
+
 /**
  * efi_var_mem_init() - set-up variable list
  *
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 4ccd26f94a..1fcc6fabb4 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -54,6 +54,17 @@ config EFI_VARIABLE_FILE_STORE
 	  Select this option if you want non-volatile UEFI variables to be
 	  stored as file /ubootefi.var on the EFI system partition.
 
+config EFI_VARIABLE_SF_STORE
+	bool "Store non-volatile UEFI variables in SPI Flash"
+	depends on SPI_FLASH
+	help
+	  Select this option if you want non-volatile UEFI variables to be
+	  stored in SPI Flash.
+	  Define CONFIG_EFI_VARIABLE_SF_OFFSET as offset in SPI Flash to use as
+	  the storage for variables. CONFIG_EFI_VAR_BUF_SIZE defines the space
+	  needed.
+
+
 config EFI_MM_COMM_TEE
 	bool "UEFI variables storage service via the trusted world"
 	depends on OPTEE
@@ -108,6 +119,13 @@ config EFI_VARIABLE_NO_STORE
 
 endchoice
 
+config EFI_VARIABLE_SF_OFFSET
+	hex "EFI variables in SPI flash offset"
+	depends on EFI_VARIABLE_SF_STORE
+	default 0x7D0000
+	help
+	  Offset from the start of the SPI Flash where EFI variables will be stored.
+
 config EFI_VARIABLES_PRESEED
 	bool "Initial values for UEFI variables"
 	depends on !EFI_MM_COMM_TEE
diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
index 8d31fc61c6..b9b715b1ff 100644
--- a/lib/efi_loader/Makefile
+++ b/lib/efi_loader/Makefile
@@ -67,6 +67,7 @@ obj-$(CONFIG_EFI_UNICODE_COLLATION_PROTOCOL2) += efi_unicode_collation.o
 obj-y += efi_var_common.o
 obj-y += efi_var_mem.o
 obj-y += efi_var_file.o
+obj-$(CONFIG_EFI_VARIABLE_SF_STORE) += efi_var_sf.o
 ifeq ($(CONFIG_EFI_MM_COMM_TEE),y)
 obj-y += efi_variable_tee.o
 else
diff --git a/lib/efi_loader/efi_var_sf.c b/lib/efi_loader/efi_var_sf.c
new file mode 100644
index 0000000000..e604a2225c
--- /dev/null
+++ b/lib/efi_loader/efi_var_sf.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * File interface for UEFI variables
+ *
+ * Copyright (c) 2023, Shantur Rtahore
+ */
+
+#define LOG_CATEGORY LOGC_EFI
+
+#include <efi_loader.h>
+#include <efi_variable.h>
+#include <spi_flash.h>
+#include <dm.h>
+
+efi_status_t efi_var_to_sf(void)
+{
+	efi_status_t ret;
+	struct efi_var_file *buf;
+	loff_t len;
+	struct udevice *sfdev;
+
+	ret = efi_var_collect(&buf, &len, EFI_VARIABLE_NON_VOLATILE);
+	if (len > EFI_VAR_BUF_SIZE) {
+		log_err("EFI var buffer length more than target SF size");
+		ret = EFI_BAD_BUFFER_SIZE;
+		goto error;
+	}
+
+	debug("%s - Got buffer to write buf->len : %d\n", __func__, buf->length);
+
+	if (ret != EFI_SUCCESS)
+		goto error;
+
+	ret = uclass_get_device(UCLASS_SPI_FLASH, 0, &sfdev);
+	if (ret)
+		goto error;
+
+	ret = spi_flash_erase_dm(sfdev, CONFIG_EFI_VARIABLE_SF_OFFSET, EFI_VAR_BUF_SIZE);
+	debug("%s - Erased SPI Flash offset %lx\n", __func__, CONFIG_EFI_VARIABLE_SF_OFFSET);
+	if (ret)
+		goto error;
+
+	ret = spi_flash_write_dm(sfdev, CONFIG_EFI_VARIABLE_SF_OFFSET, len, buf);
+	debug("%s - Wrote buffer to SPI Flash : %ld\n", __func__, ret);
+
+	if (ret)
+		goto error;
+
+	ret = EFI_SUCCESS;
+error:
+	if (ret)
+		log_err("Failed to persist EFI variables in SF\n");
+	free(buf);
+	return ret;
+}
+
+efi_status_t efi_var_from_sf(void)
+{
+	struct efi_var_file *buf;
+	efi_status_t ret;
+	struct udevice *sfdev;
+
+	buf = calloc(1, EFI_VAR_BUF_SIZE);
+	if (!buf) {
+		log_err("Out of memory\n");
+		return EFI_OUT_OF_RESOURCES;
+	}
+
+	ret = uclass_get_device(UCLASS_SPI_FLASH, 0, &sfdev);
+	if (ret)
+		goto error;
+
+	ret = spi_flash_read_dm(sfdev, CONFIG_EFI_VARIABLE_SF_OFFSET,
+		EFI_VAR_BUF_SIZE, buf);
+
+	debug("%s - read buffer buf->length: %x\n", __func__, buf->length);
+
+	if (ret || buf->length < sizeof(struct efi_var_file)) {
+		log_err("Failed to load EFI variables\n");
+		goto error;
+	}
+
+	ret = efi_var_restore(buf, false);
+	if (ret != EFI_SUCCESS)
+		log_err("Invalid EFI variables file\n");
+
+	ret = EFI_SUCCESS;
+error:
+	free(buf);
+	return ret;
+}
diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
index 7fa444451d..0f85962f05 100644
--- a/lib/efi_loader/efi_variable.c
+++ b/lib/efi_loader/efi_variable.c
@@ -360,6 +360,8 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
 	if (attributes & EFI_VARIABLE_NON_VOLATILE) {
 #ifdef CONFIG_EFI_VARIABLE_FILE_STORE
 		efi_var_to_file();
+#elif CONFIG_EFI_VARIABLE_SF_STORE
+		efi_var_to_sf();
 #endif
 	}
 
@@ -471,6 +473,8 @@ efi_status_t efi_init_variables(void)
 
 #ifdef CONFIG_EFI_VARIABLE_FILE_STORE
 	ret = efi_var_from_file();
+#elif CONFIG_EFI_VARIABLE_SF_STORE
+	ret = efi_var_from_sf();
 #else
 	ret = EFI_SUCCESS;
 #endif
-- 
2.40.1