drm/i915/execlists: Record the active CCID from before reset

If we cannot trust the reset will flush out the CS event queue such that
process_csb() reports an accurate view of HW, we will need to search the
active and pending contexts to determine which was actually running at
the time we issued the reset.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200505084629.31365-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_engine_types.h

@@ -179,6 +179,11 @@ struct intel_engine_execlists {
 	 */
 	u32 error_interrupt;
 
+	/**
+	 * @reset_ccid: Active CCID [EXECLISTS_STATUS_HI] at the time of reset
+	 */
+	u32 reset_ccid;
+
 	/**
 	 * @no_priolist: priority lists disabled
 	 */

drivers/gpu/drm/i915/gt/intel_lrc.c

@@ -4074,6 +4074,8 @@ static void execlists_reset_prepare(struct intel_engine_cs *engine)
 	 */
 	ring_set_paused(engine, 1);
 	intel_engine_stop_cs(engine);
+
+	engine->execlists.reset_ccid = active_ccid(engine);
 }
 
 static void __reset_stop_ring(u32 *regs, const struct intel_engine_cs *engine)
@@ -4116,7 +4118,7 @@ static void __execlists_reset(struct intel_engine_cs *engine, bool stalled)
 	 * its request, it was still running at the time of the
 	 * reset and will have been clobbered.
 	 */
-	rq = execlists_active(execlists);
+	rq = active_context(engine, engine->execlists.reset_ccid);
 	if (!rq)
 		goto unwind;