linux-kernel - [PATCH v7 4/9] drm_print: wrap drm_*_dbg in dyndbg descriptor factory macro

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Message-Id: <20220912052852.1123868-5-jim.cromie@gmail.com>
Date:   Sun, 11 Sep 2022 23:28:47 -0600
From:   Jim Cromie <jim.cromie@...il.com>
To:     jbaron@...mai.com, gregkh@...uxfoundation.org,
        dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
        intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     daniel.vetter@...ll.ch, seanpaul@...omium.org, robdclark@...il.com,
        linux@...musvillemoes.dk, joe@...ches.com,
        Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH v7 4/9] drm_print: wrap drm_*_dbg in dyndbg descriptor factory macro

For CONFIG_DRM_USE_DYNAMIC_DEBUG=y, wrap __drm_dbg() & __drm_dev_dbg()
in one of dyndbg's Factory macros: _dynamic_func_call_no_desc().

This adds the callsite descriptor into the code, and an entry for each
into /proc/dynamic_debug/control.

  #> echo class DRM_UT_ATOMIC +p > /proc/dynamic_debug/control

CONFIG_DRM_USE_DYNAMIC_DEBUG=y/n is configurable because of the .data
footprint cost of per-callsite control; 56 bytes/site * ~2k for i915,
~4k callsites for amdgpu.  This is large enough that a kernel builder
might not want it.

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 drivers/gpu/drm/Kconfig  | 12 ++++++++++++
 drivers/gpu/drm/Makefile |  2 ++
 include/drm/drm_print.h  | 12 ++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 6c2256e8474b..2438e0dccfa1 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -50,6 +50,18 @@ config DRM_DEBUG_MM
 
 	  If in doubt, say "N".
 
+config DRM_USE_DYNAMIC_DEBUG
+	bool "use dynamic debug to implement drm.debug"
+	default y
+	depends on DRM
+	depends on DYNAMIC_DEBUG || DYNAMIC_DEBUG_CORE
+	depends on JUMP_LABEL
+	help
+	  Use dynamic-debug to avoid drm_debug_enabled() runtime overheads.
+	  Due to callsite counts in DRM drivers (~4k in amdgpu) and 56
+	  bytes per callsite, the .data costs can be substantial, and
+	  are therefore configurable.
+
 config DRM_DEBUG_SELFTEST
 	tristate "kselftests for DRM"
 	depends on DRM
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index e7af358e6dda..6828197967a6 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -3,6 +3,8 @@
 # Makefile for the drm device driver.  This driver provides support for the
 # Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
 
+CFLAGS-$(CONFIG_DRM_USE_DYNAMIC_DEBUG)	+= -DDYNAMIC_DEBUG_MODULE
+
 drm-y       :=	drm_aperture.o drm_auth.o drm_cache.o \
 		drm_file.o drm_gem.o drm_ioctl.o \
 		drm_drv.o \
diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
index c429c258c957..2d2cef76b5c1 100644
--- a/include/drm/drm_print.h
+++ b/include/drm/drm_print.h
@@ -384,8 +384,14 @@ void __drm_dev_dbg(const struct device *dev, enum drm_debug_category category,
 	}								\
 })
 
+#if !defined(CONFIG_DRM_USE_DYNAMIC_DEBUG)
 #define drm_dev_dbg(dev, cat, fmt, ...)				\
 	__drm_dev_dbg(dev, cat, fmt, ##__VA_ARGS__)
+#else
+#define drm_dev_dbg(dev, cat, fmt, ...)				\
+	_dynamic_func_call_no_desc(fmt, __drm_dev_dbg,			\
+				   dev, cat, fmt, ##__VA_ARGS__)
+#endif
 
 /**
  * DRM_DEV_DEBUG() - Debug output for generic drm code
@@ -492,7 +498,13 @@ void ___drm_dbg(enum drm_debug_category category, const char *format, ...);
 __printf(1, 2)
 void __drm_err(const char *format, ...);
 
+#if !defined(CONFIG_DRM_USE_DYNAMIC_DEBUG)
 #define __drm_dbg(fmt, ...)		___drm_dbg(fmt, ##__VA_ARGS__)
+#else
+#define __drm_dbg(cat, fmt, ...)					\
+	_dynamic_func_call_no_desc(fmt, ___drm_dbg,			\
+				   cat, fmt, ##__VA_ARGS__)
+#endif
 
 /* Macros to make printk easier */
 
-- 
2.37.3