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drm: Disable dynamic debug as broken
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CONFIG_DRM_USE_DYNAMIC_DEBUG breaks debug prints for (at least modular)
drm drivers. The debug prints can be reinstated by manually frobbing
/sys/module/drm/parameters/debug after the fact, but at that point the
damage is done and all debugs from driver probe are lost. This makes
drivers totally undebuggable.

There's a more complete fix in progress [1], with further details, but
we need this fixed in stable kernels. Mark the feature as broken and
disable it by default, with hopes distros follow suit and disable it as
well.

[1] https://lore.kernel.org/r/20230125203743.564009-1-jim.cromie@gmail.com

Fixes: 84ec672 ("drm_print: wrap drm_*_dbg in dyndbg descriptor factory macro")
Cc: Jim Cromie <jim.cromie@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v6.1+
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Jim Cromie <jim.cromie@gmail.com>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230207143337.2126678-1-jani.nikula@intel.com
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Ville Syrjälä authored and Jani Nikula committed Feb 13, 2023
1 parent 7484a5b commit bb2ff6c
Showing 1 changed file with 2 additions and 1 deletion.
3 changes: 2 additions & 1 deletion drivers/gpu/drm/Kconfig
Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,8 @@ config DRM_DEBUG_MM

config DRM_USE_DYNAMIC_DEBUG
bool "use dynamic debug to implement drm.debug"
default y
default n
depends on BROKEN
depends on DRM
depends on DYNAMIC_DEBUG || DYNAMIC_DEBUG_CORE
depends on JUMP_LABEL
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