drm: Pull the test on drm_debug in the logging macros

In the logging code, we are currently checking is we need to output in
drm_ut_debug_printk(). This is too late. The problem is that when we write
something like:

    DRM_DEBUG_DRIVER("ELD on [CONNECTOR:%d:%s], [ENCODER:%d:%s]\n",
                     connector->base.id,
                     drm_get_connector_name(connector),
                     connector->encoder->base.id,
                     drm_get_encoder_name(connector->encoder));

We start by evaluating the arguments (so call drm_get_connector_name() and
drm_get_connector_name()) before ending up in drm_ut_debug_printk() which will
then does nothing.

This means we execute a lot of instructions (drm_get_connector_name(), in turn,
calls snprintf() for example) to happily discard them in the normal case,
drm.debug=0.

So, let's put the test on drm_debug earlier, in the macros themselves.
Sprinkle an unlikely() as well for good measure.
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_stub.c

@@ -97,26 +97,24 @@ int drm_err(const char *func, const char *format, ...)
 }
 EXPORT_SYMBOL(drm_err);
 
-void drm_ut_debug_printk(unsigned int request_level,
-			 const char *prefix,
+void drm_ut_debug_printk(const char *prefix,
 			 const char *function_name,
 			 const char *format, ...)
 {
 	struct va_format vaf;
 	va_list args;
 
-	if (drm_debug & request_level) {
-		va_start(args, format);
-		vaf.fmt = format;
-		vaf.va = &args;
-
-		if (function_name)
-			printk(KERN_DEBUG "[%s:%s], %pV", prefix,
-			       function_name, &vaf);
-		else
-			printk(KERN_DEBUG "%pV", &vaf);
-		va_end(args);
-	}
+	va_start(args, format);
+	vaf.fmt = format;
+	vaf.va = &args;
+
+	if (function_name)
+		printk(KERN_DEBUG "[%s:%s], %pV", prefix,
+		       function_name, &vaf);
+	else
+		printk(KERN_DEBUG "%pV", &vaf);
+
+	va_end(args);
 }
 EXPORT_SYMBOL(drm_ut_debug_printk);
 

include/drm/drmP.h

@@ -121,9 +121,8 @@ struct videomode;
 #define DRM_UT_KMS		0x04
 #define DRM_UT_PRIME		0x08
 
-extern __printf(4, 5)
-void drm_ut_debug_printk(unsigned int request_level,
-			 const char *prefix,
+extern __printf(3, 4)
+void drm_ut_debug_printk(const char *prefix,
 			 const char *function_name,
 			 const char *format, ...);
 extern __printf(2, 3)
@@ -209,24 +208,28 @@ int drm_err(const char *func, const char *format, ...);
 #if DRM_DEBUG_CODE
 #define DRM_DEBUG(fmt, args...)						\
 	do {								\
-		drm_ut_debug_printk(DRM_UT_CORE, DRM_NAME, 		\
-					__func__, fmt, ##args);		\
+		if (unlikely(drm_debug & DRM_UT_CORE))			\
+			drm_ut_debug_printk(DRM_NAME, __func__,		\
+					    fmt, ##args);		\
 	} while (0)
 
 #define DRM_DEBUG_DRIVER(fmt, args...)					\
 	do {								\
-		drm_ut_debug_printk(DRM_UT_DRIVER, DRM_NAME,		\
-					__func__, fmt, ##args);		\
+		if (unlikely(drm_debug & DRM_UT_DRIVER))		\
+			drm_ut_debug_printk(DRM_NAME, __func__,		\
+					    fmt, ##args);		\
 	} while (0)
-#define DRM_DEBUG_KMS(fmt, args...)				\
+#define DRM_DEBUG_KMS(fmt, args...)					\
 	do {								\
-		drm_ut_debug_printk(DRM_UT_KMS, DRM_NAME, 		\
-					 __func__, fmt, ##args);	\
+		if (unlikely(drm_debug & DRM_UT_KMS))			\
+			drm_ut_debug_printk(DRM_NAME, __func__,		\
+					    fmt, ##args);		\
 	} while (0)
 #define DRM_DEBUG_PRIME(fmt, args...)					\
 	do {								\
-		drm_ut_debug_printk(DRM_UT_PRIME, DRM_NAME,		\
-					__func__, fmt, ##args);		\
+		if (unlikely(drm_debug & DRM_UT_PRIME))			\
+			drm_ut_debug_printk(DRM_NAME, __func__,		\
+					    fmt, ##args);		\
 	} while (0)
 #else
 #define DRM_DEBUG_DRIVER(fmt, args...) do { } while (0)