[Intel-gfx] [PATCH] drm/i915: fix whitelist selftests with readonly registers

[Chris Wilson]

From: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

When a register is readonly there is not much we can tell about its
value (apart from its default value?). This can be covered by tests
exercising the value of the register from userspace.

For PS_INVOCATION_COUNT we've got the following piglit tests :

   KHR-GL45.pipeline_statistics_query_tests_ARB.functional_fragment_shader_invocations

Vulkan CTS tests :

   dEQP-VK.query_pool.statistics_query.fragment_shader_invocations.*

v2: Use a local to shrink under 80cols.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Fixes: 86554f48e511 ("drm/i915/selftests: Verify whitelist of context registers")
Tested-by: Anuj Phogat <anuj.phogat at gmail.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
Fixes is a bit much, since the test is still very much nerfed and not
complemented by a test for read-only non-priv registers...
-Chris
---
 drivers/gpu/drm/i915/gt/selftest_workarounds.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/selftest_workarounds.c b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
index f12cb20fe785..b933d831eeb1 100644
--- a/drivers/gpu/drm/i915/gt/selftest_workarounds.c
+++ b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
@@ -926,7 +926,12 @@ check_whitelisted_registers(struct intel_engine_cs *engine,
 
 	err = 0;
 	for (i = 0; i < engine->whitelist.count; i++) {
-		if (!fn(engine, a[i], b[i], engine->whitelist.list[i].reg))
+		const struct i915_wa *wa = &engine->whitelist.list[i];
+
+		if (i915_mmio_reg_offset(wa->reg) & RING_FORCE_TO_NONPRIV_RD)
+			continue;
+
+		if (!fn(engine, a[i], b[i], wa->reg))
 			err = -EINVAL;
 	}
 
-- 
2.20.1