Add concept of console output log levels

Create new LOG_LEVEL build option, which controls the amount of
console output compiled into the build. This should be one of the
following:

    0  (LOG_LEVEL_NONE)
    10 (LOG_LEVEL_NOTICE)
    20 (LOG_LEVEL_ERROR)
    30 (LOG_LEVEL_WARNING)
    40 (LOG_LEVEL_INFO)
    50 (LOG_LEVEL_VERBOSE)

All log output up to and including the log level is compiled into the
build. The default value is 40 in debug builds and 20 in release
builds.

Complement the existing INFO, WARN and ERROR console output macros
with NOTICE and VERBOSE macros, which are conditionally compiled in
depending on the value of LOG_LEVEL.

Fixes ARM-software/tf-issues#232

Change-Id: I951e2f333e7b90fc4b1060741d9a6db699d5aa72

Makefile

@@ -80,8 +80,12 @@ export Q
 
 ifneq (${DEBUG}, 0)
 	BUILD_TYPE	:=	debug
+	# Use LOG_LEVEL_INFO by default for debug builds
+	LOG_LEVEL	:=	40
 else
 	BUILD_TYPE	:=	release
+	# Use LOG_LEVEL_NOTICE by default for release builds
+	LOG_LEVEL	:=	20
 endif
 
 # Default build string (git branch and commit)
@@ -213,6 +217,9 @@ $(eval $(call add_define,ARM_GIC_ARCH))
 $(eval $(call assert_boolean,ASM_ASSERTION))
 $(eval $(call add_define,ASM_ASSERTION))
 
+# Process LOG_LEVEL flag
+$(eval $(call add_define,LOG_LEVEL))
+
 ASFLAGS			+= 	-nostdinc -ffreestanding -Wa,--fatal-warnings	\
 				-Werror -Wmissing-include-dirs			\
 				-mgeneral-regs-only -D__ASSEMBLY__		\

docs/user-guide.md

@@ -146,6 +146,19 @@ performed.
 *   `DEBUG`: Chooses between a debug and release build. It can take either 0
     (release) or 1 (debug) as values. 0 is the default
 
+*   `LOG_LEVEL`: Chooses the log level, which controls the amount of console log
+    output compiled into the build. This should be one of the following:
+
+        0  (LOG_LEVEL_NONE)
+        10 (LOG_LEVEL_NOTICE)
+        20 (LOG_LEVEL_ERROR)
+        30 (LOG_LEVEL_WARNING)
+        40 (LOG_LEVEL_INFO)
+        50 (LOG_LEVEL_VERBOSE)
+
+    All log output up to and including the log level is compiled into the build.
+    The default value is 40 in debug builds and 20 in release builds.
+
 *   `NS_TIMER_SWITCH`: Enable save and restore for non-secure timer register
     contents upon world switch. It can take either 0 (don't save and restore) or
     1 (do save and restore). 0 is the default. An SPD could set this to 1 if it

include/common/debug.h

@@ -33,24 +33,53 @@
 
 #include <stdio.h>
 
-/* If building the project with DEBUG disabled the INFO and WARN macros
- * won't produce any output. The ERROR macro is always enabled.
- * The format expected is the same as for printf().
- * INFO("Info %s.\n", "message")    -> INFO: Info message.
- * WARN("Warning %s.\n", "message") -> WARN: Warning message.
- * ERROR("Error %s.\n", "message")  -> ERROR: Error message.
- *
- * TODO : add debug levels.
+/* The log output macros print output to the console. These macros produce
+ * compiled log output only if the LOG_LEVEL defined in the makefile (or the
+ * make command line) is greater or equal than the level required for that
+ * type of log output.
+ * The format expected is the same as for printf(). For example:
+ * INFO("Info %s.\n", "message")    -> INFO:    Info message.
+ * WARN("Warning %s.\n", "message") -> WARNING: Warning message.
  */
-#if DEBUG
- #define INFO(...)	tf_printf("INFO: " __VA_ARGS__)
- #define WARN(...)	tf_printf("WARN: " __VA_ARGS__)
+
+#define LOG_LEVEL_NONE			0
+#define LOG_LEVEL_ERROR			10
+#define LOG_LEVEL_NOTICE		20
+#define LOG_LEVEL_WARNING		30
+#define LOG_LEVEL_INFO			40
+#define LOG_LEVEL_VERBOSE		50
+
+
+#if LOG_LEVEL >= LOG_LEVEL_NOTICE
+# define NOTICE(...)	tf_printf("NOTICE:  " __VA_ARGS__)
 #else
- #define INFO(...)
- #define WARN(...)
+# define NOTICE(...)
+#endif
+
+#if LOG_LEVEL >= LOG_LEVEL_ERROR
+# define ERROR(...)	tf_printf("ERROR:   " __VA_ARGS__)
+#else
+# define ERROR(...)
+#endif
+
+#if LOG_LEVEL >= LOG_LEVEL_WARNING
+# define WARN(...)	tf_printf("WARNING: " __VA_ARGS__)
+#else
+# define WARN(...)
+#endif
+
+#if LOG_LEVEL >= LOG_LEVEL_INFO
+# define INFO(...)	tf_printf("INFO:    " __VA_ARGS__)
+#else
+# define INFO(...)
+#endif
+
+#if LOG_LEVEL >= LOG_LEVEL_VERBOSE
+# define VERBOSE(...)	tf_printf("VERBOSE: " __VA_ARGS__)
+#else
+# define VERBOSE(...)
 #endif
 
-#define ERROR(...)	tf_printf("ERROR: " __VA_ARGS__)
 
 void __dead2 do_panic(void);
 #define panic()	do_panic()