drivers/intel/fsp2_0: Add option to control debug log level using CBFS

This commit relies on newly added Kconfig option,
USE_CBFS_FILE_OPTION_BACKEND, which allows controlling the FSP debug
log level using CBFS options (RAW binary files).

The default log-level is setup in coreboot while stitching the CBFS
option binaries depending upon the coreboot log-level.

Following files will be used to determine the log levels:

- fsp_pcd_debug_level: For the overall FSP debug log level.

- fsp_mrc_debug_level: For the MRC (Memory Reference Code) debug log
  level.

In absense of these files, the FSP console log-level is determine by
calling into fsp_map_console_log_level API.

The values in these files should correspond to the FSP_LOG_LEVEL_* enum
values.

This change allows for more flexibility in controlling the FSP debug log
level, especially in cases of debugging silicon firmware issues with a
debug AP FW binary.

This capability is particularly useful when debugging issues that
require examining both silicon and MRC logs simultaneously.

BUG=b:227151510
TEST=Able to control the FSP debug log based on CBFS options

To inject the fsp_pcd_debug_level and fsp_mrc_debug_level CBFS files
with the desired log level, run:

```
cbfstool image-fatcat.serial.bin add-int -i 5 -n option/fsp_pcd_debug_level

cbfstool image-fatcat.serial.bin add-int -i 5 -n option/fsp_mrc_debug_level
```

With both fsp_pcd_debug_level and fsp_mrc_debug_level present in the RO
CBFS, both the silicon firmware and MRC behave as debug binaries.

To verify the presence of both log-level RAW CBFS binaries in the CBFS RO
slot, run:

```
sudo cbfstool fatcat/image-rex0.serial.bin print | grep fsp_
```

This should output:

```
option/fsp_mrc_debug_level            0x88e40    raw                 8 none
option/fsp_pcd_debug_level            0x2a7400   raw                 8 none
```

Change-Id: I2c14d26021dd0048fa24024119df857e216f18bd
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/86001
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>

src/drivers/intel/fsp2_0/debug.c

@@ -6,6 +6,7 @@
 #include <cpu/x86/mtrr.h>
 #include <fsp/debug.h>
 #include <fsp/util.h>
+#include <option.h>
 
 enum fsp_call_phase {
 	BEFORE_FSP_CALL,
@@ -178,3 +179,13 @@ void fsp_debug_after_notify(efi_return_status_t status)
 
 	display_mtrrs();
 }
+
+enum fsp_log_level fsp_get_pcd_debug_log_level(void)
+{
+	return get_uint_option("fsp_pcd_debug_level", fsp_map_console_log_level());
+}
+
+enum fsp_log_level fsp_get_mrc_debug_log_level(void)
+{
+	return get_uint_option("fsp_mrc_debug_level", fsp_map_console_log_level());
+}

src/drivers/intel/fsp2_0/include/fsp/debug.h

@@ -63,4 +63,45 @@ void gpio_snapshot(void);
 /* Callback to verify that current GPIO configuration matches the saved snapshot */
 size_t gpio_verify_snapshot(void);
 
+/*
+ * Retrieve fsp_pcd_debug_level file from option backend (e.g. CBFS) to identify the log-level
+ * used for outputting FSP debug messages.
+ *
+ * 1. Critical errors, need action etc., FSP_LOG_LEVEL_ERR aka value 1
+ * 2. #1 including warnings, FSP_LOG_LEVEL_ERR_WARN aka value 2
+ * 3. #2 including additional informational messages, FSP_LOG_LEVEL_ERR_WARN_INFO aka value 3
+ *
+ * The default log-level is setup in coreboot while stitching the CBFS option binaries
+ * depending upon the coreboot log-level. One can override that using below example:
+ *
+ * Here is an example of adding fsp_pcd_debug_level option binary file into the RO-CBFS
+ * to specify the FSP log-level:
+ *  - cbfstool <AP FW image> add-int -i <log-level> -n option/fsp_pcd_debug_level
+ *
+ * If OPTION_BACKEND_NONE then the then, use log levels will be determined by
+ * calling into fsp_map_console_log_level API.
+ */
+enum fsp_log_level fsp_get_pcd_debug_log_level(void);
+/*
+ * Retrieve fsp_mrc_debug_level file from option backend (e.g. CBFS) to identify the log-level
+ * used for outputting FSP debug messages.
+ *
+ * 1. Critical errors, need action etc., FSP_LOG_LEVEL_ERR aka value 1
+ * 2. #1 including warnings, FSP_LOG_LEVEL_ERR_WARN aka value 2
+ * 3. #2 including additional informational messages, FSP_LOG_LEVEL_ERR_WARN_INFO aka value 3
+ * 4. #3 including event logs, FSP_LOG_LEVEL_ERR_WARN_INFO_EVENT aka value 4
+ * 5. Use FSP_LOG_LEVEL_VERBOSE aka 5 for all types of debug messages.
+ *
+ * The default log-level is setup in coreboot while stitching the CBFS option binaries
+ * depending upon the coreboot log-level. One can override that using below example:
+ *
+ * Here is an example of adding fsp_mrc_debug_level option binary file into the RO-CBFS
+ * to specify the FSP log-level:
+ *  - cbfstool <AP FW image> add-int -i <log-level> -n option/fsp_mrc_debug_level
+ *
+ * If OPTION_BACKEND_NONE then the then, use log levels will be determined by
+ * calling into fsp_map_console_log_level API.
+ */
+enum fsp_log_level fsp_get_mrc_debug_log_level(void);
+
 #endif /* _FSP2_0_DEBUG_H_ */