[igt-dev] [PATCH i-g-t] i915/gem_exec_balancer: Disable pre-parser for rewritten batches

[Chris Wilson]

As we rewrite the batches on the fly to implement the non-preemptible
lock, we need to tell Tigerlake to read the batch afresh each time.
Amusingly, the disable is a part of an arb-check, so we have to be
careful not to include the arbitration point inside our unpreemptible
loop.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 tests/i915/gem_exec_balancer.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/tests/i915/gem_exec_balancer.c b/tests/i915/gem_exec_balancer.c
index 026f8347e..0e3b52900 100644
--- a/tests/i915/gem_exec_balancer.c
+++ b/tests/i915/gem_exec_balancer.c
@@ -1350,6 +1350,11 @@ static void __bonded_dual(int i915,
 	*out = cycles;
 }
 
+static uint32_t preparser_disable(void)
+{
+	return 0x5 << 23 | 1 << 8 | 1; /* preparser masked disable */
+}
+
 static uint32_t sync_from(int i915, uint32_t addr, uint32_t target)
 {
 	uint32_t handle = gem_create(i915, 4096);
@@ -1363,14 +1368,14 @@ static uint32_t sync_from(int i915, uint32_t addr, uint32_t target)
 	*cs++ = 0;
 	*cs++ = 0;
 
-	*cs++ = MI_NOOP;
+	*cs++ = preparser_disable();
 	*cs++ = MI_NOOP;
 	*cs++ = MI_NOOP;
 	*cs++ = MI_NOOP;
 
 	/* wait for them to cancel us */
 	*cs++ = MI_BATCH_BUFFER_START | 1 << 8 | 1;
-	*cs++ = addr + 16;
+	*cs++ = addr + 24;
 	*cs++ = 0;
 
 	/* self-heal */
@@ -1393,14 +1398,14 @@ static uint32_t sync_to(int i915, uint32_t addr, uint32_t target)
 
 	cs = map = gem_mmap__device_coherent(i915, handle, 0, 4096, PROT_WRITE);
 
-	*cs++ = MI_NOOP;
+	*cs++ = preparser_disable();
 	*cs++ = MI_NOOP;
 	*cs++ = MI_NOOP;
 	*cs++ = MI_NOOP;
 
 	/* wait to be cancelled */
 	*cs++ = MI_BATCH_BUFFER_START | 1 << 8 | 1;
-	*cs++ = addr;
+	*cs++ = addr + 8;
 	*cs++ = 0;
 
 	/* cancel their spin as a compliment */
-- 
2.27.0.rc2