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Date:   Fri, 13 Aug 2021 09:17:08 -0600
From:   Jim Cromie <>
        Maarten Lankhorst <>,
        Maxime Ripard <>,
        Thomas Zimmermann <>,
        David Airlie <>,
        Daniel Vetter <>,
        Alex Deucher <>,
        Christian K├Ânig <>,
        "Pan, Xinhui" <>,
        Harry Wentland <>,
        Leo Li <>,
        Zhenyu Wang <>,
        Zhi Wang <>,
        Jani Nikula <>,
        Joonas Lahtinen <>,
        Rodrigo Vivi <>,
        Jason Baron <>,
        Hawking Zhang <>,
        Tao Zhou <>, Huang Rui <>,
        Kevin Wang <>,
        Likun Gao <>,
        Chengming Gui <>,
        Aaron Liu <>,
        Jim Cromie <>,
        John Clements <>,
        Ashley Thomas <>,
        Wyatt Wood <>,
        Qingqing Zhuo <>,
        Aurabindo Pillai <>,
        Johan Hovold <>, Jessica Yu <>,
        Joe Perches <>,
        Nick Desaulniers <>,
        Miguel Ojeda <>,
        Andrew Morton <>,
        Masahiro Yamada <>,
        Peter Zijlstra <>,
        Andy Shevchenko <>,
        "Paul E. McKenney" <>,
        Tetsuo Handa <>,
        Thomas Gleixner <>,
        Vitor Massaru Iha <>,
        Sedat Dilek <>,
        Mel Gorman <>,
        Marco Elver <>,
        Alexander Potapenko <>,
        Brendan Higgins <>,
        Arvind Sankar <>,
        "Matthew Wilcox (Oracle)" <>,
        Jiri Olsa <>,
        Patricia Alfonso <>,
        Palmer Dabbelt <>,
        Johannes Berg <>,
        Arnd Bergmann <>,,,,,
Subject: [PATCH v5 0/9] dyndbg: add DEFINE_DYNAMIC_DEBUG_CATEGORIES and use in DRM

hi Jason, Greg, Daniel, dri-everyone,

drm_debug_enabled() is called a lot (by drm-debug api) to do unlikely
bit-tests to selectively enable debug printing; this is a good job for
This patchset enables the use of dynamic-debug to avoid those
drm_debug_enabled() overheads, if CONFIG_DRM_USE_DYNAMIC_DEBUG=y.

v5: much rework

- based on Daniel Vetter's feedback, not RFC anymore. (except last one)

- move POC bit_map callback code into dynamic_debug
  add .data to struct kernel_param
  a declarative interface for bits => control-queries
  this is all new functionality.

  adds selectivity/control to existing categorizations

  replace DRM_UT_<CAT> (an enum)
  with DRM_CAT_<CAT>   (a prefix string, cpp-prepended to format)
  _UT_ still present, drm_debug_enabled() still used
  change __drm_debug param-var to read DDD_CATEGORIES's param-var
  might suffice to keep parallel schemes coherent.
- RFC add tracer func as syslog alternate
  test_dynamic_debug.ko: uses tracer for observability, does selftest
  has some misuse risk; calling pr_debug recursively.

v4: (brown-bagger, various fixes after snips)
v3: fixes missed SOB, && on BOL, commit-log tweaks

Doing so creates many new pr_debug callsites,
otherwise i915 has ~120 prdbgs, and drm has just 1;

  bash-5.1# modprobe i915
  dyndbg:   8 debug prints in module video
  dyndbg: 305 debug prints in module drm
  dyndbg: 207 debug prints in module drm_kms_helper
  dyndbg:   2 debug prints in module ttm
  dyndbg: 1720 debug prints in module i915

On amdgpu, enabling it adds ~3200 prdbgs, currently at 56 bytes each.
So CONFIG_DRM_USE_DYNAMIC_DEBUG=y affects resource requirements.
Im working on a diet-plan.

Im running this patchset bare-metal on an i7/i915 laptop & an
r9/amdgpu desktop (both as loadable modules).  I booted the amdgpu box

BOOT_IMAGE=(hd2,gpt2)/vmlinuz-5.14.0-rc4-d7a-00009-g5db471cba844 \
     root=UUID=mumble ro \
     rootflags=subvol=root00 rhgb \
     dynamic_debug.verbose=3 main.dyndbg=+p \
     amdgpu.debug=1 amdgpu.test=1 \
     "amdgpu.dyndbg=format ^[ +p"

That last line enables ~1700 prdbg callsites with a format like '[DML'
etc at boot, and amdgpu.test=1 triggers 90 seconds of tests, yielding
~76k prdbgs in 409 seconds, before I turned them off with:

  echo module amdgpu -p > /proc/dynamic_debug/control

Its worth noting, this changes the dyndbg-state underneath settings
applied with `echo > parameters/debug`; the latter is qualitatively
writeonly, maybe a param_get should return "NA" "-1"

this merged cleanly, on top of
commit d65ef4634e5c795a6a4df1d198992c70e9692fb3 (drm-tip/drm-tip)

Jim Cromie (9):
  drm/print: fixup spelling in a comment
  moduleparam: add data member to struct kernel_param
  dyndbg: add DEFINE_DYNAMIC_DEBUG_CATEGORIES and callbacks
  i915/gvt: remove spaces in pr_debug "gvt: core:" etc prefixes
  i915/gvt: use DEFINE_DYNAMIC_DEBUG_CATEGORIES to create "gvt:core:"
    etc categories
  amdgpu: use DEFINE_DYNAMIC_DEBUG_CATEGORIES to control categorized
  drm_print: add choice to use dynamic debug in drm-debug
  amdgpu_ucode: reduce number of pr_debug calls
  dyndbg: RFC add tracer facility RFC

 drivers/gpu/drm/Kconfig                       |  13 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.c     | 293 ++++++++++--------
 .../gpu/drm/amd/display/dc/core/dc_debug.c    |  44 ++-
 drivers/gpu/drm/drm_print.c                   |  49 ++-
 drivers/gpu/drm/i915/gvt/Makefile             |   4 +
 drivers/gpu/drm/i915/gvt/debug.h              |  18 +-
 drivers/gpu/drm/i915/i915_params.c            |  35 +++
 include/drm/drm_print.h                       | 143 +++++++--
 include/linux/dynamic_debug.h                 |  82 ++++-
 include/linux/moduleparam.h                   |  11 +-
 lib/Kconfig.debug                             |  10 +
 lib/Makefile                                  |   1 +
 lib/dynamic_debug.c                           | 171 ++++++++--
 lib/test_dynamic_debug.c                      | 247 +++++++++++++++
 14 files changed, 901 insertions(+), 220 deletions(-)
 create mode 100644 lib/test_dynamic_debug.c


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