drm/xe: Make p2pdma distance check verbose via dynamic debug

pci_p2pdma_distance() can optionally print details about how it
computed the ACS/PCIe topology distance between the two devices, but
xe_dma_buf_attach() always called it with verbose set to false,
silently hiding useful diagnostics whenever a dma-buf attach unset
attach->peer2peer.

Tie the verbose argument to a dedicated dynamic-debug callsite tagged
"xe dma-buf p2p debug" (in addition to keeping the existing
DRM_UT_DRIVER category as a default), so the extra p2pdma distance
logging can be switched on without a recompile in any of the following
ways:

 - Enable the whole DRIVER category for xe via drm.debug, which is
   already used elsewhere in the driver:

     # echo 0x10 > /sys/module/drm/parameters/debug

 - Enable dynamic debug for the whole file:

     # echo 'file xe_dma_buf.c +p' > \
             /sys/kernel/debug/dynamic_debug/control

 - Enable dynamic debug for just this callsite by function name:

     # echo 'func xe_dma_buf_attach +p' > \
             /sys/kernel/debug/dynamic_debug/control

 - Enable dynamic debug by matching the format string used to
   register the callsite:

     # echo 'format "xe dma-buf p2p debug" +p' > \
             /sys/kernel/debug/dynamic_debug/control

 - Enable it at boot via the dyndbg= kernel command line parameter:

     dyndbg="func xe_dma_buf_attach +p"

Any of the above flips verbose_p2p_dist to true for that attach call,
causing pci_p2pdma_distance() to log its distance calculation without
requiring the whole DRM_UT_DRIVER category to be enabled.

v2:
- Guard the _dynamic_func_call() invocation and
  xe_ddebug_flip_bool() with a CONFIG_DYNAMIC_DEBUG check so the
  build does not break when dynamic debug is disabled. (Sashiko-bot)

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Assisted-by: LLM
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Link: https://patch.msgid.link/20260914114617.112012-1-thomas.hellstrom@linux.intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

0 files changed, 0 insertions, 0 deletions