Merge tag 'drm-intel-next-2018-04-13' of git://anongit.freedesktop.org/drm/drm-intel into drm-next

First drm/i915 feature batch heading for v4.18:

- drm-next backmerge to fix build (Rodrigo)
- GPU documentation improvements (Kevin)
- GuC and HuC refactoring, host/GuC communication, logging, fixes, and more
  (mostly Michal and Michał, also Jackie, Michel and Piotr)
- PSR and PSR2 enabling and fixes (DK, José, Rodrigo and Chris)
- Selftest updates (Chris, Daniele)
- DPLL management refactoring (Lucas)
- DP MST fixes (Lyude and DK)
- Watermark refactoring and changes to support NV12 (Mahesh)
- NV12 prep work (Chandra)
- Icelake Combo PHY enablers (Manasi)
- Perf OA refactoring and ICL enabling (Lionel)
- ICL enabling (Oscar, Paulo, Nabendu, Mika, Kelvin, Michel)
- Workarounds refactoring (Oscar)
- HDCP fixes and improvements (Ramalingam, Radhakrishna)
- Power management fixes (Imre)
- Various display fixes (Maarten, Ville, Vidya, Jani, Gaurav)
- debugfs for FIFO underrun clearing (Maarten)
- Execlist improvements (Chris)
- Reset improvements (Chris)
- Plenty of things here and there I overlooked and/or didn't understand... (Everyone)

Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/87lgd2cze8.fsf@intel.com

1 files changed, 29 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 0414228cd2b5..c74f5df3fb5a 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -81,6 +81,35 @@ enum {
  * but this remains just a hint as the kernel may choose a new location for
  * any object in the future.
  *
+ * At the level of talking to the hardware, submitting a batchbuffer for the
+ * GPU to execute is to add content to a buffer from which the HW
+ * command streamer is reading.
+ *
+ * 1. Add a command to load the HW context. For Logical Ring Contexts, i.e.
+ *    Execlists, this command is not placed on the same buffer as the
+ *    remaining items.
+ *
+ * 2. Add a command to invalidate caches to the buffer.
+ *
+ * 3. Add a batchbuffer start command to the buffer; the start command is
+ *    essentially a token together with the GPU address of the batchbuffer
+ *    to be executed.
+ *
+ * 4. Add a pipeline flush to the buffer.
+ *
+ * 5. Add a memory write command to the buffer to record when the GPU
+ *    is done executing the batchbuffer. The memory write writes the
+ *    global sequence number of the request, ``i915_request::global_seqno``;
+ *    the i915 driver uses the current value in the register to determine
+ *    if the GPU has completed the batchbuffer.
+ *
+ * 6. Add a user interrupt command to the buffer. This command instructs
+ *    the GPU to issue an interrupt when the command, pipeline flush and
+ *    memory write are completed.
+ *
+ * 7. Inform the hardware of the additional commands added to the buffer
+ *    (by updating the tail pointer).
+ *
  * Processing an execbuf ioctl is conceptually split up into a few phases.
  *
  * 1. Validation - Ensure all the pointers, handles and flags are valid.