drm/xe: Add WA BB to capture active context utilization

Context Timestamp (CTX_TIMESTAMP) in the LRC accumulates the run ticks
of the context, but only gets updated when the context switches out. In
order to check how long a context has been active before it switches
out, two things are required:

(1) Determine if the context is running:

To do so, we program the WA BB to set an initial value for CTX_TIMESTAMP
in the LRC. The value chosen is 1 since 0 is the initial value when the
LRC is initialized. During a query, we just check for this value to
determine if the context is active. If the context switched out, it
would overwrite this location with the actual CTX_TIMESTAMP MMIO value.
Note that WA BB runs as the last part of the context restore, so reusing
this LRC location will not clobber anything.

(2) Calculate the time that the context has been active for:

The CTX_TIMESTAMP ticks only when the context is active. If a context is
active, we just use the CTX_TIMESTAMP MMIO as the new value of
utilization. While doing so, we need to read the CTX_TIMESTAMP MMIO
for the specific engine instance. Since we do not know which instance
the context is running on until it is scheduled, we also read the
ENGINE_ID MMIO in the WA BB and store it in the PPHSWP.

Using the above 2 instructions in a WA BB, capture active context
utilization.

v2: (Matt Brost)
- This breaks TDR, fix it by saving the CTX_TIMESTAMP register
  "drm/xe: Save CTX_TIMESTAMP mmio value instead of LRC value"
- Drop tile from LRC if using gt
  "drm/xe: Save the gt pointer in LRC and drop the tile"

v3:
- Remove helpers for bb_per_ctx_ptr (Matt)
- Add define for context active value (Matt)
- Use 64 bit CTX TIMESTAMP for platforms that support it. For platforms
  that don't, live with the rare race. (Matt, Lucas)
- Convert engine id to hwe and get the MMIO value (Lucas)
- Correct commit message on when WA BB runs (Lucas)

v4:
- s/GRAPHICS_VER(...)/xe->info.has_64bit_timestamp/ (Matt)
- Drop support for active utilization on a VF (CI failure)
- In xe_lrc_init ensure the lrc value is 0 to begin with (CI regression)

v5:
- Minor checkpatch fix
- Squash into previous commit and make TDR use 32-bit time
- Update code comment to match commit msg

Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4532
Cc: <stable@vger.kernel.org> # v6.13+
Suggested-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20250509161159.2173069-8-umesh.nerlige.ramappa@intel.com
(cherry picked from commit 82b98cadb01f63cdb159e596ec06866d00f8e8c7)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

0 files changed, 0 insertions, 0 deletions