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    Subject[PATCH v10 07/10] drm_print: instrument drm_debug_enabled
    Date
    Duplicate drm_debug_enabled() code into both "basic" and "dyndbg"
    ifdef branches. Then add a pr_debug("todo: ...") into the "dyndbg"
    branch.

    Then convert the "dyndbg" branch's code to a macro, so that the
    pr_debug() get its callsite info from the invoking function, instead
    of from drm_debug_enabled() itself.

    This gives us unique callsite info for the 8 remaining users of
    drm_debug_enabled(), and lets us enable them individually to see how
    much logging traffic they generate. The oft-visited callsites can
    then be reviewed for runtime cost and possible optimizations.

    Heres what we get:

    bash-5.1# modprobe drm
    dyndbg: 384 debug prints in module drm
    bash-5.1# grep todo: /proc/dynamic_debug/control
    drivers/gpu/drm/drm_edid.c:1843 [drm]connector_bad_edid =_ "todo: maybe avoid via dyndbg\012"
    drivers/gpu/drm/drm_print.c:309 [drm]___drm_dbg =p "todo: maybe avoid via dyndbg\012"
    drivers/gpu/drm/drm_print.c:286 [drm]__drm_dev_dbg =p "todo: maybe avoid via dyndbg\012"
    drivers/gpu/drm/drm_vblank.c:1491 [drm]drm_vblank_restore =_ "todo: maybe avoid via dyndbg\012"
    drivers/gpu/drm/drm_vblank.c:787 [drm]drm_crtc_vblank_helper_get_vblank_timestamp_internal =_ "todo: maybe avoid via dyndbg\012"
    drivers/gpu/drm/drm_vblank.c:410 [drm]drm_crtc_accurate_vblank_count =_ "todo: maybe avoid via dyndbg\012"
    drivers/gpu/drm/drm_atomic_uapi.c:1457 [drm]drm_mode_atomic_ioctl =_ "todo: maybe avoid via dyndbg\012"
    drivers/gpu/drm/drm_edid_load.c:178 [drm]edid_load =_ "todo: maybe avoid via dyndbg\012"

    At quick glance, edid won't qualify, drm_print might, drm_vblank is
    strongest chance, maybe atomic-ioctl too.

    Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
    ---
    include/drm/drm_print.h | 17 +++++++++++------
    1 file changed, 11 insertions(+), 6 deletions(-)

    diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
    index 392cff7cb95c..a902bd4d8c55 100644
    --- a/include/drm/drm_print.h
    +++ b/include/drm/drm_print.h
    @@ -381,6 +381,11 @@ enum drm_debug_category {
    #define DRM_DBG_CAT_DP DRM_UT_DP
    #define DRM_DBG_CAT_DRMRES DRM_UT_DRMRES

    +static inline bool drm_debug_enabled(enum drm_debug_category category)
    +{
    + return unlikely(__drm_debug & category);
    +}
    +
    #else /* CONFIG_DRM_USE_DYNAMIC_DEBUG */

    /* join prefix + format in cpp so dyndbg can see it */
    @@ -414,12 +419,13 @@ enum drm_debug_category {
    #define DRM_DBG_CAT_DP "drm:dp: "
    #define DRM_DBG_CAT_DRMRES "drm:res: "

    -#endif /* CONFIG_DRM_USE_DYNAMIC_DEBUG */
    +#define drm_debug_enabled(category) \
    + ({ \
    + pr_debug("todo: maybe avoid via dyndbg\n"); \
    + unlikely(__drm_debug & (category)); \
    + })

    -static inline bool drm_debug_enabled(enum drm_debug_category category)
    -{
    - return unlikely(__drm_debug & category);
    -}
    +#endif /* CONFIG_DRM_USE_DYNAMIC_DEBUG */

    /*
    * struct device based logging
    @@ -582,7 +588,6 @@ void __drm_dev_dbg(const struct device *dev, enum drm_debug_category category,
    #define drm_dbg_drmres(drm, fmt, ...) \
    drm_dev_dbg((drm) ? (drm)->dev : NULL, DRM_DBG_CAT_DRMRES, fmt, ##__VA_ARGS__)

    -
    /*
    * printk based logging
    *
    --
    2.31.1
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