src/lib/fw_config: Change fw_config sources priority

Request fw_config values from various sources (as enabled via Kconfig)
until a valid value has been read.
With this change, Chrome EC CBI takes precedence over CBFS fw_config.

TEST=select both configs and check fallback behavior.
1. select both FW_CONFIG_SOURCE_CHROMEEC_CBI and FW_CONFIG_SOURCE_CBFS
2. check log for reading fw_config from CBI and CBFS

Signed-off-by: Wonkyu Kim <wonkyu.kim@intel.com>
Change-Id: I215c13a4fcb9dc3b94f73c770e704d4e353e9cff
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58833
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

2 files changed, 27 insertions, 27 deletions

diff --git a/src/Kconfig b/src/Kconfig
index 89849eca02fe..e30152d2e5df 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -395,16 +395,6 @@ config FW_CONFIG
 	  Enable support for probing devices with fw_config.  This is a simple
 	  bitmask broken into fields and options for probing.
 
-config FW_CONFIG_SOURCE_CBFS
-	bool "Obtain Firmware Configuration value from CBFS"
-	depends on FW_CONFIG
-	default n
-	help
-	  With this option enabled coreboot will look for the 32bit firmware
-	  configuration value in CBFS at the selected prefix with the file name
-	  "fw_config".  This option will override other sources and allow the
-	  local image to preempt the mainboard selected source.
-
 config FW_CONFIG_SOURCE_CHROMEEC_CBI
 	bool "Obtain Firmware Configuration value from Google Chrome EC CBI"
 	depends on FW_CONFIG && EC_GOOGLE_CHROMEEC
@@ -415,6 +405,17 @@ config FW_CONFIG_SOURCE_CHROMEEC_CBI
 	  is not tried if FW_CONFIG_SOURCE_CBFS is enabled and the value was
 	  found in CBFS.
 
+config FW_CONFIG_SOURCE_CBFS
+	bool "Obtain Firmware Configuration value from CBFS"
+	depends on FW_CONFIG
+	default n
+	help
+	  With this option enabled coreboot will look for the 32bit firmware
+	  configuration value in CBFS at the selected prefix with the file name
+	  "fw_config".  This option will override other sources and allow the
+	  local image to preempt the mainboard selected source and can be used as
+	  FW_CONFIG_SOURCE_CHROMEEC_CBI fallback option.
+
 config HAVE_RAMPAYLOAD
 	bool
 
diff --git a/src/lib/fw_config.c b/src/lib/fw_config.c
index 8e45c004fbfa..3546736b7b36 100644
--- a/src/lib/fw_config.c
+++ b/src/lib/fw_config.c
@@ -21,30 +21,29 @@ uint64_t fw_config_get(void)
 	if (fw_config_value_initialized)
 		return fw_config_value;
 	fw_config_value_initialized = true;
+	fw_config_value = UNDEFINED_FW_CONFIG;
+
+	/* Read the value from EC CBI. */
+	if (CONFIG(FW_CONFIG_SOURCE_CHROMEEC_CBI)) {
+		if (google_chromeec_cbi_get_fw_config(&fw_config_value))
+			printk(BIOS_WARNING, "%s: Could not get fw_config from CBI\n",
+				__func__);
+		else
+			printk(BIOS_INFO, "FW_CONFIG value from CBI is 0x%" PRIx64 "\n",
+				fw_config_value);
+	}
 
 	/* Look in CBFS to allow override of value. */
-	if (CONFIG(FW_CONFIG_SOURCE_CBFS)) {
+	if (CONFIG(FW_CONFIG_SOURCE_CBFS) && fw_config_value == UNDEFINED_FW_CONFIG) {
 		if (cbfs_load(CONFIG_CBFS_PREFIX "/fw_config", &fw_config_value,
-			      sizeof(fw_config_value)) != sizeof(fw_config_value)) {
+			      sizeof(fw_config_value)) != sizeof(fw_config_value))
 			printk(BIOS_WARNING, "%s: Could not get fw_config from CBFS\n",
-			       __func__);
-			fw_config_value = UNDEFINED_FW_CONFIG;
-		} else {
+				__func__);
+		else
 			printk(BIOS_INFO, "FW_CONFIG value from CBFS is 0x%" PRIx64 "\n",
-			       fw_config_value);
-			return fw_config_value;
-		}
-	}
-
-	/* Read the value from EC CBI. */
-	if (CONFIG(FW_CONFIG_SOURCE_CHROMEEC_CBI)) {
-		if (google_chromeec_cbi_get_fw_config(&fw_config_value)) {
-			printk(BIOS_WARNING, "%s: Could not get fw_config from EC\n", __func__);
-			fw_config_value = UNDEFINED_FW_CONFIG;
-		}
+				fw_config_value);
 	}
 
-	printk(BIOS_INFO, "FW_CONFIG value is 0x%" PRIx64 "\n", fw_config_value);
 	return fw_config_value;
 }