[RFC v2] drm: Enable dynamic debug for DRM_[DEV]_DEBUG*

Robert Bragg robert at sixbynine.org
Wed Dec 7 18:35:29 UTC 2016


This is still missing corresponding documentation changes, and I haven't
moved anything to drm_print.h yet, as suggested.

Sending out with a few functional improvements first to get agreement
before documenting anything (changes summarised in v2: section below)

In particular, affecting the output format, I stole an idea from Tvrtko
Ursulin to have the prefix for messages be based on the driver name,
such as "[i915]" instead of always being "[drm]".

Depending on peoples thoughts on compatibility, we could consider
removing the prefix given that the dynamic debug control interface has a
way of specifying that messages should include a module name, function
or line info like:

echo "module i915 +mfp" > dynamic_debug/control

That would enable all i915 debug messages with a module and function
prefix.

A trade-off would be that anyone only using the drm.drm_debug interface
to control messages would loose some information. If we really wanted we
could have the best of both by adding a utility printing api that can
recognise when printing due to a dynamic debug control query vs
drm.drm_debug to conditionally add the prefix.

--- >8 --- (git am --scissors)

Dynamic debug messages (ref: Documentation/dynamic-debug-howto.txt)
allow fine grained control over which debug messages are enabled with
runtime control through /sysfs/kernel/debug/dynamic_debug/control

This provides more control than the current drm.drm_debug parameter
which for some use cases is impractical to use given how chatty
some drm debug categories are.

For example all debug messages in i915_drm.c can be enabled with:
echo "file i915_perf.c +p" > dynamic_debug/control

This doesn't strictly maintain format compatibility with the previous
debug messages since the category is now added as part of the prefix
like "[drm][kms] No FB found". Adding the categories with a consistent
format makes it possible to enable categories with a dynamic debug
query like: echo "format [kms] +p" > dynamic_debug/control

This maintains support for enabling debug messages using the drm_debug
parameter. If dynamic debug is not enabled via CONFIG_DYNAMIC_DEBUG the
debug messages essentially work as before, except with the inclusion of
categories in the format strings as described above.

This removes the drm_[dev_]printk wrappers considering that the dynamic
debug macros are only useful if they can track the __FILE__, __func__
and __LINE__ where they are called. The wrapper didn't seem necessary in
the DRM_UT_NONE case with no category flag.

The non _DEV macros are no longer defined in terms of passing NULL to a
_DEV variant to avoid have the core.c dev_printk implementation adding
"(NULL device *)". The previous drm_[dev_]prink function used to handle
this as a special case.

Instead of using DRM_NAME to add [drm] to the start of every message,
the prefix is now based on module_name(THIS_MODULE) so it will be [drm]
or e.g. [i915] for the Intel driver. Later we might consider removing
the prefix altogether considering that the dynamic debug control
interface has a way of optionally adding the module, function or line to
the formatting of messages.

v2:
    Add categories to format like "[drm][kms] No FB found"
    Only single conditional call per message (macros expand to less code)
    Uses __dynamic_pr_debug/dev_dbg for dynamic formatting features
    Use module name for msg prefix like [drm] or [i915]

Signed-off-by: Robert Bragg <robert at sixbynine.org>
Cc: dri-devel at lists.freedesktop.org
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/drm_drv.c |  47 -----------
 include/drm/drmP.h        | 202 +++++++++++++++++++++++++++++-----------------
 2 files changed, 127 insertions(+), 122 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index f74b7d0..25d00aa 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -65,53 +65,6 @@ static struct idr drm_minors_idr;
 
 static struct dentry *drm_debugfs_root;
 
-#define DRM_PRINTK_FMT "[" DRM_NAME ":%s]%s %pV"
-
-void drm_dev_printk(const struct device *dev, const char *level,
-		    unsigned int category, const char *function_name,
-		    const char *prefix, const char *format, ...)
-{
-	struct va_format vaf;
-	va_list args;
-
-	if (category != DRM_UT_NONE && !(drm_debug & category))
-		return;
-
-	va_start(args, format);
-	vaf.fmt = format;
-	vaf.va = &args;
-
-	if (dev)
-		dev_printk(level, dev, DRM_PRINTK_FMT, function_name, prefix,
-			   &vaf);
-	else
-		printk("%s" DRM_PRINTK_FMT, level, function_name, prefix, &vaf);
-
-	va_end(args);
-}
-EXPORT_SYMBOL(drm_dev_printk);
-
-void drm_printk(const char *level, unsigned int category,
-		const char *format, ...)
-{
-	struct va_format vaf;
-	va_list args;
-
-	if (category != DRM_UT_NONE && !(drm_debug & category))
-		return;
-
-	va_start(args, format);
-	vaf.fmt = format;
-	vaf.va = &args;
-
-	printk("%s" "[" DRM_NAME ":%ps]%s %pV",
-	       level, __builtin_return_address(0),
-	       strcmp(level, KERN_ERR) == 0 ? " *ERROR*" : "", &vaf);
-
-	va_end(args);
-}
-EXPORT_SYMBOL(drm_printk);
-
 /*
  * DRM Minors
  * A DRM device can provide several char-dev interfaces on the DRM-Major. Each
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index a9cfd33..0416114 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -58,6 +58,7 @@
 #include <linux/vmalloc.h>
 #include <linux/workqueue.h>
 #include <linux/dma-fence.h>
+#include <linux/dynamic_debug.h>
 
 #include <asm/mman.h>
 #include <asm/pgalloc.h>
@@ -129,15 +130,22 @@ struct dma_buf_attachment;
  * run-time by echoing the debug value in its sysfs node:
  *   # echo 0xf > /sys/module/drm/parameters/debug
  */
-#define DRM_UT_NONE		0x00
 #define DRM_UT_CORE 		0x01
+#define _DRM_UT_core		0x01
 #define DRM_UT_DRIVER		0x02
+#define _DRM_UT_drv		0x02
 #define DRM_UT_KMS		0x04
+#define _DRM_UT_kms		0x04
 #define DRM_UT_PRIME		0x08
+#define _DRM_UT_prime		0x08
 #define DRM_UT_ATOMIC		0x10
+#define _DRM_UT_atomic		0x10
 #define DRM_UT_VBL		0x20
+#define _DRM_UT_vbl		0x20
 #define DRM_UT_STATE		0x40
 
+#define _DRM_PREFIX module_name(THIS_MODULE)
+
 /***********************************************************************/
 /** \name DRM template customization defaults */
 /*@{*/
@@ -146,25 +154,19 @@ struct dma_buf_attachment;
 /** \name Macros to make printk easier */
 /*@{*/
 
-#define _DRM_PRINTK(once, level, fmt, ...)				\
-	do {								\
-		printk##once(KERN_##level "[" DRM_NAME "] " fmt,	\
-			     ##__VA_ARGS__);				\
-	} while (0)
-
-#define DRM_INFO(fmt, ...)						\
-	_DRM_PRINTK(, INFO, fmt, ##__VA_ARGS__)
-#define DRM_NOTE(fmt, ...)						\
-	_DRM_PRINTK(, NOTICE, fmt, ##__VA_ARGS__)
-#define DRM_WARN(fmt, ...)						\
-	_DRM_PRINTK(, WARNING, fmt, ##__VA_ARGS__)
-
-#define DRM_INFO_ONCE(fmt, ...)						\
-	_DRM_PRINTK(_once, INFO, fmt, ##__VA_ARGS__)
-#define DRM_NOTE_ONCE(fmt, ...)						\
-	_DRM_PRINTK(_once, NOTICE, fmt, ##__VA_ARGS__)
-#define DRM_WARN_ONCE(fmt, ...)						\
-	_DRM_PRINTK(_once, WARNING, fmt, ##__VA_ARGS__)
+#define DRM_INFO(fmt, args...)						\
+	pr_info("[%s] " fmt, _DRM_PREFIX, ##args)
+#define DRM_NOTE(fmt, args...)						\
+	pr_notice("[%s] " fmt, _DRM_PREFIX, ##args)
+#define DRM_WARN(fmt, args...)						\
+	pr_warn("[%s] " fmt, _DRM_PREFIX, ##args)
+
+#define DRM_INFO_ONCE(fmt, args...)					\
+	pr_info_once("[%s] " fmt, _DRM_PREFIX, ##args)
+#define DRM_NOTE_ONCE(fmt, args...)					\
+	pr_notice_once("[%s] " fmt, _DRM_PREFIX, ##args)
+#define DRM_WARN_ONCE(fmt, args...)					\
+	pr_warn_once("[%s] " fmt, _DRM_PREFIX, ##args)
 
 /**
  * Error output.
@@ -172,11 +174,10 @@ struct dma_buf_attachment;
  * \param fmt printf() like format string.
  * \param arg arguments
  */
-#define DRM_DEV_ERROR(dev, fmt, ...)					\
-	drm_dev_printk(dev, KERN_ERR, DRM_UT_NONE, __func__, " *ERROR*",\
-		       fmt, ##__VA_ARGS__)
-#define DRM_ERROR(fmt, ...)						\
-	drm_printk(KERN_ERR, DRM_UT_NONE, fmt,	##__VA_ARGS__)
+#define DRM_DEV_ERROR(dev, fmt, args...)				\
+	dev_err(dev, "[%s:%s]*ERROR*" fmt, _DRM_PREFIX, __func__, ##args)
+#define DRM_ERROR(fmt, args...)						\
+	pr_err("[%s:%s]*ERROR*" fmt, _DRM_PREFIX, __func__, ##args)
 
 /**
  * Rate limited error output.  Like DRM_ERROR() but won't flood the log.
@@ -184,81 +185,129 @@ struct dma_buf_attachment;
  * \param fmt printf() like format string.
  * \param arg arguments
  */
-#define DRM_DEV_ERROR_RATELIMITED(dev, fmt, ...)			\
+#define DRM_DEV_ERROR_RATELIMITED(dev, fmt, args...)			\
 ({									\
 	static DEFINE_RATELIMIT_STATE(_rs,				\
 				      DEFAULT_RATELIMIT_INTERVAL,	\
 				      DEFAULT_RATELIMIT_BURST);		\
 									\
 	if (__ratelimit(&_rs))						\
-		DRM_DEV_ERROR(dev, fmt, ##__VA_ARGS__);			\
+		DRM_DEV_ERROR(dev, fmt, ##args);			\
 })
-#define DRM_ERROR_RATELIMITED(fmt, ...)					\
-	DRM_DEV_ERROR_RATELIMITED(NULL, fmt, ##__VA_ARGS__)
-
-#define DRM_DEV_INFO(dev, fmt, ...)					\
-	drm_dev_printk(dev, KERN_INFO, DRM_UT_NONE, __func__, "", fmt,	\
-		       ##__VA_ARGS__)
-
-#define DRM_DEV_INFO_ONCE(dev, fmt, ...)				\
+#define DRM_ERROR_RATELIMITED(fmt, args...)				\
 ({									\
-	static bool __print_once __read_mostly;				\
-	if (!__print_once) {						\
-		__print_once = true;					\
-		DRM_DEV_INFO(dev, fmt, ##__VA_ARGS__);			\
-	}								\
+	static DEFINE_RATELIMIT_STATE(_rs,				\
+				      DEFAULT_RATELIMIT_INTERVAL,	\
+				      DEFAULT_RATELIMIT_BURST);		\
+									\
+	if (__ratelimit(&_rs))						\
+		DRM_ERROR(fmt, ##args);					\
 })
 
+#define DRM_DEV_INFO(dev, fmt, args...)					\
+	dev_info(dev, "[%s:%s] " fmt, _DRM_PREFIX, __func__, ##args)
+
+#define DRM_DEV_INFO_ONCE(dev, fmt, args...)				\
+	dev_info_once(dev, "[%s:%s] " fmt, _DRM_PREFIX, __func__, ##args)
+
 /**
  * Debug output.
  *
  * \param fmt printf() like format string.
  * \param arg arguments
  */
+
+#if defined(CONFIG_DYNAMIC_DEBUG)
+#define DRM_DEF_DYN_DEBUG_DATA(name, fmt)				\
+	DEFINE_DYNAMIC_DEBUG_METADATA(name, fmt);
+#define DRM_DYN_DEBUG_BRANCH(descriptor)				\
+	DYNAMIC_DEBUG_BRANCH(descriptor)
+
+#define __drm_dyn_dev_dbg(descriptor, dev, fmt, args...)		\
+	__dynamic_dev_dbg(descriptor, dev, fmt, ##args)
+#define __drm_dyn_pr_debug(descriptor, fmt, args...)			\
+	__dynamic_pr_debug(descriptor, fmt, ##args)
+#else
+#define DRM_DEF_DYN_DEBUG_DATA(name, fmt)	do {} while(0)
+#define DRM_DYN_DEBUG_BRANCH(descriptor)	0
+
+#define __drm_dyn_dev_dbg(descriptor, dev, fmt, args...)		\
+	dev_dbg(dev, fmt, ##args)
+#define __drm_dyn_pr_debug(descriptor, fmt, args...)			\
+	pr_debug(fmt, ##args)
+#endif
+
+/* If modifying, note the duplication of the format strings for the
+ * dynamic debug meta data and for passing to printk. We don't
+ * deref descriptor->format to handle building without
+ * CONFIG_DYNAMIC_DEBUG
+ */
+#define _DRM_DEV_DEBUG(dev, cat, fmt, args...)				\
+({									\
+	DRM_DEF_DYN_DEBUG_DATA(descriptor, "[%s:%s]["#cat"] " fmt);	\
+	if (DRM_DYN_DEBUG_BRANCH(descriptor) ||				\
+	    unlikely(drm_debug & _DRM_UT_##cat)) {			\
+		__drm_dyn_dev_dbg(&descriptor, dev,			\
+				  "[%s:%s]["#cat"] " fmt,		\
+				  _DRM_PREFIX, __func__, ##args);	\
+	}								\
+})
+#define _DRM_DEBUG(cat, fmt, args...)					\
+({									\
+	DRM_DEF_DYN_DEBUG_DATA(descriptor, "[%s:%s]["#cat"] " fmt);	\
+	if (DRM_DYN_DEBUG_BRANCH(descriptor) ||				\
+	    unlikely(drm_debug & _DRM_UT_##cat)) {			\
+		__drm_dyn_pr_debug(&descriptor,				\
+				   "[%s:%s]["#cat"] " fmt,		\
+				   _DRM_PREFIX, __func__, ##args);	\
+	}								\
+})
+
 #define DRM_DEV_DEBUG(dev, fmt, args...)				\
-	drm_dev_printk(dev, KERN_DEBUG, DRM_UT_CORE, __func__, "", fmt,	\
-		       ##args)
-#define DRM_DEBUG(fmt, ...)						\
-	drm_printk(KERN_DEBUG, DRM_UT_CORE, fmt, ##__VA_ARGS__)
+	_DRM_DEV_DEBUG(dev, core, fmt, ##args)
+#define DRM_DEBUG(fmt, args...)						\
+	_DRM_DEBUG(core, fmt, ##args)
 
 #define DRM_DEV_DEBUG_DRIVER(dev, fmt, args...)				\
-	drm_dev_printk(dev, KERN_DEBUG, DRM_UT_DRIVER, __func__, "",	\
-		       fmt, ##args)
-#define DRM_DEBUG_DRIVER(fmt, ...)					\
-	drm_printk(KERN_DEBUG, DRM_UT_DRIVER, fmt, ##__VA_ARGS__)
+	_DRM_DEV_DEBUG(dev, drv, fmt, ##args)
+#define DRM_DEBUG_DRIVER(fmt, args...)					\
+	_DRM_DEBUG(drv, fmt, ##args)
 
 #define DRM_DEV_DEBUG_KMS(dev, fmt, args...)				\
-	drm_dev_printk(dev, KERN_DEBUG, DRM_UT_KMS, __func__, "", fmt,	\
-		       ##args)
-#define DRM_DEBUG_KMS(fmt, ...)					\
-	drm_printk(KERN_DEBUG, DRM_UT_KMS, fmt, ##__VA_ARGS__)
+	_DRM_DEV_DEBUG(dev, kms, fmt, ##args)
+#define DRM_DEBUG_KMS(fmt, args...)					\
+	_DRM_DEBUG(kms, fmt, ##args)
 
 #define DRM_DEV_DEBUG_PRIME(dev, fmt, args...)				\
-	drm_dev_printk(dev, KERN_DEBUG, DRM_UT_PRIME, __func__, "",	\
-		       fmt, ##args)
-#define DRM_DEBUG_PRIME(fmt, ...)					\
-	drm_printk(KERN_DEBUG, DRM_UT_PRIME, fmt, ##__VA_ARGS__)
+	_DRM_DEV_DEBUG(dev, prime, fmt, ##args)
+#define DRM_DEBUG_PRIME(fmt, args...)					\
+	_DRM_DEBUG(prime, fmt, ##args)
 
 #define DRM_DEV_DEBUG_ATOMIC(dev, fmt, args...)				\
-	drm_dev_printk(dev, KERN_DEBUG, DRM_UT_ATOMIC, __func__, "",	\
-		       fmt, ##args)
-#define DRM_DEBUG_ATOMIC(fmt, ...)					\
-	drm_printk(KERN_DEBUG, DRM_UT_ATOMIC, fmt, ##__VA_ARGS__)
+	_DRM_DEV_DEBUG(dev, atomic, fmt, ##args)
+#define DRM_DEBUG_ATOMIC(fmt, args...)					\
+	_DRM_DEBUG(atomic, fmt, ##args)
 
 #define DRM_DEV_DEBUG_VBL(dev, fmt, args...)				\
-	drm_dev_printk(dev, KERN_DEBUG, DRM_UT_VBL, __func__, "", fmt,	\
-		       ##args)
-#define DRM_DEBUG_VBL(fmt, ...)					\
-	drm_printk(KERN_DEBUG, DRM_UT_VBL, fmt, ##__VA_ARGS__)
+	_DRM_DEV_DEBUG(dev, vbl, fmt, ##args)
+#define DRM_DEBUG_VBL(fmt, args...)					\
+	_DRM_DEBUG(vbl, fmt, ##args)
 
-#define _DRM_DEV_DEFINE_DEBUG_RATELIMITED(dev, level, fmt, args...)	\
+#define _DRM_DEV_DEFINE_DEBUG_RATELIMITED(dev, category, fmt, args...)	\
 ({									\
 	static DEFINE_RATELIMIT_STATE(_rs,				\
 				      DEFAULT_RATELIMIT_INTERVAL,	\
 				      DEFAULT_RATELIMIT_BURST);		\
 	if (__ratelimit(&_rs))						\
-		drm_dev_printk(dev, KERN_DEBUG, DRM_UT_ ## level,	\
-			       __func__, "", fmt, ##args);		\
+		_DRM_DEV_DEBUG(dev, category, fmt, ##args);		\
+})
+#define _DRM_DEFINE_DEBUG_RATELIMITED(category, fmt, args...)	\
+({									\
+	static DEFINE_RATELIMIT_STATE(_rs,				\
+				      DEFAULT_RATELIMIT_INTERVAL,	\
+				      DEFAULT_RATELIMIT_BURST);		\
+	if (__ratelimit(&_rs))						\
+		_DRM_DEBUG(category, fmt, ##args);			\
 })
 
 /**
@@ -268,21 +317,24 @@ struct dma_buf_attachment;
  * \param arg arguments
  */
 #define DRM_DEV_DEBUG_RATELIMITED(dev, fmt, args...)			\
-	DEV__DRM_DEFINE_DEBUG_RATELIMITED(dev, CORE, fmt, ##args)
+	_DRM_DEFINE_DEBUG_RATELIMITED(dev, core, fmt, ##args)
 #define DRM_DEBUG_RATELIMITED(fmt, args...)				\
-	DRM_DEV_DEBUG_RATELIMITED(NULL, fmt, ##args)
+	_DRM_DEFINE_DEBUG_RATELIMITED(core, fmt, ##args)
+
 #define DRM_DEV_DEBUG_DRIVER_RATELIMITED(dev, fmt, args...)		\
-	_DRM_DEV_DEFINE_DEBUG_RATELIMITED(dev, DRIVER, fmt, ##args)
+	_DRM_DEV_DEFINE_DEBUG_RATELIMITED(dev, drv, fmt, ##args)
 #define DRM_DEBUG_DRIVER_RATELIMITED(fmt, args...)			\
-	DRM_DEV_DEBUG_DRIVER_RATELIMITED(NULL, fmt, ##args)
+	_DRM_DEV_DEFINE_DEBUG_RATELIMITED(drv, fmt, ##args)
+
 #define DRM_DEV_DEBUG_KMS_RATELIMITED(dev, fmt, args...)		\
-	_DRM_DEV_DEFINE_DEBUG_RATELIMITED(dev, KMS, fmt, ##args)
+	_DRM_DEV_DEFINE_DEBUG_RATELIMITED(dev, kms, fmt, ##args)
 #define DRM_DEBUG_KMS_RATELIMITED(fmt, args...)				\
-	DRM_DEV_DEBUG_KMS_RATELIMITED(NULL, fmt, ##args)
+	_DRM_DEFINE_DEBUG_RATELIMITED(kms, fmt, ##args)
+
 #define DRM_DEV_DEBUG_PRIME_RATELIMITED(dev, fmt, args...)		\
-	_DRM_DEV_DEFINE_DEBUG_RATELIMITED(dev, PRIME, fmt, ##args)
+	_DRM_DEV_DEFINE_DEBUG_RATELIMITED(dev, prime, fmt, ##args)
 #define DRM_DEBUG_PRIME_RATELIMITED(fmt, args...)			\
-	DRM_DEV_DEBUG_PRIME_RATELIMITED(NULL, fmt, ##args)
+	_DRM_DEFINE_DEBUG_RATELIMITED(prime, fmt, ##args)
 
 /* Format strings and argument splitters to simplify printing
  * various "complex" objects
-- 
2.10.2



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