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>

2 files changed, 27 insertions, 26 deletions

diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index dc2c6095d850..81ed83288557 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/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);
 
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 665176e68b48..cde156293d9d 100644
--- a/include/drm/drmP.h
+++ b/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)