From b229ea58cbe2f107dc0a7e2c7cdce193f7166b47 Mon Sep 17 00:00:00 2001
From: Maxime Ripard <mripard@kernel.org>
Date: Fri, 28 Jul 2023 11:06:24 +0200
Subject: [PATCH] drm/vc4: tests: pv-muxing: Document test scenario
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We've had a couple of tests that weren't really obvious, nor did they
document what they were supposed to test. Document that to make it
hopefully more obvious.
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: MaÃra Canal <mairacanal@riseup.net>
Link: https://lore.kernel.org/r/20230728-kms-kunit-actions-rework-v3-11-952565ccccfe@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
.../gpu/drm/vc4/tests/vc4_test_pv_muxing.c | 22 +++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/drivers/gpu/drm/vc4/tests/vc4_test_pv_muxing.c b/drivers/gpu/drm/vc4/tests/vc4_test_pv_muxing.c
index 5f9f5626329d0..61622e9510312 100644
--- a/drivers/gpu/drm/vc4/tests/vc4_test_pv_muxing.c
+++ b/drivers/gpu/drm/vc4/tests/vc4_test_pv_muxing.c
@@ -845,6 +845,13 @@ static void drm_test_vc5_pv_muxing_bugs_subsequent_crtc_enable(struct kunit *tes
KUNIT_EXPECT_NE(test, hdmi0_channel, hdmi1_channel);
}
+/*
+ * This test makes sure that we never change the FIFO of an active HVS
+ * channel if we disable a FIFO with a lower index.
+ *
+ * Doing so would result in a FIFO stall and would disrupt an output
+ * supposed to be unaffected by the commit.
+ */
static void drm_test_vc5_pv_muxing_bugs_stable_fifo(struct kunit *test)
{
struct drm_modeset_acquire_ctx *ctx;
@@ -924,6 +931,21 @@ static void drm_test_vc5_pv_muxing_bugs_stable_fifo(struct kunit *test)
}
}
+/*
+ * Test that if we affect a single output, only the CRTC state of that
+ * output will be pulled in the global atomic state.
+ *
+ * This is relevant for two things:
+ *
+ * - If we don't have that state at all, we are unlikely to affect the
+ * FIFO muxing. This is somewhat redundant with
+ * drm_test_vc5_pv_muxing_bugs_stable_fifo()
+ *
+ * - KMS waits for page flips to occur on all the CRTC found in the
+ * CRTC state. Since the CRTC is unaffected, we would over-wait, but
+ * most importantly run into corner cases like waiting on an
+ * inactive CRTC that never completes.
+ */
static void
drm_test_vc5_pv_muxing_bugs_subsequent_crtc_enable_too_many_crtc_state(struct kunit *test)
{
--
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