linux-kernel - [PATCH 5.15 184/201] drm/amd/display: Fix surface optimization regression on Carrizo

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Message-Id: <20220727161035.401781717@linuxfoundation.org>
Date:   Wed, 27 Jul 2022 18:11:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tom St Denis <tom.stdenis@....com>,
        Harry Wentland <harry.wentland@....com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Mario Limonciello <Mario.Limonciello@....com>
Subject: [PATCH 5.15 184/201] drm/amd/display: Fix surface optimization regression on Carrizo

From: Nicholas Kazlauskas <nicholas.kazlauskas@....com>

commit 62e5a7e2333a9f5395f6a9db766b7b06c949fe7a upstream.

[Why]
DCE legacy optimization path isn't well tested under new DC optimization
flow which can result in underflow occuring when initializing X11 on
Carrizo.

[How]
Retain the legacy optimization flow for DCE and keep the new one for DCN
to satisfy optimizations being correctly applied for ASIC that can
support it.

Fixes: 34316c1e561db0 ("drm/amd/display: Optimize bandwidth on following fast update")
Reported-by: Tom St Denis <tom.stdenis@....com>
Tested-by: Tom St Denis <tom.stdenis@....com>
Reviewed-by: Harry Wentland <harry.wentland@....com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Cc: Mario Limonciello <Mario.Limonciello@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/amd/display/dc/core/dc.c |   15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -2979,8 +2979,13 @@ void dc_commit_updates_for_stream(struct
 			if (new_pipe->plane_state && new_pipe->plane_state != old_pipe->plane_state)
 				new_pipe->plane_state->force_full_update = true;
 		}
-	} else if (update_type == UPDATE_TYPE_FAST) {
-		/* Previous frame finished and HW is ready for optimization. */
+	} else if (update_type == UPDATE_TYPE_FAST && dc_ctx->dce_version >= DCE_VERSION_MAX) {
+		/*
+		 * Previous frame finished and HW is ready for optimization.
+		 *
+		 * Only relevant for DCN behavior where we can guarantee the optimization
+		 * is safe to apply - retain the legacy behavior for DCE.
+		 */
 		dc_post_update_surfaces_to_stream(dc);
 	}
 
@@ -3039,6 +3044,12 @@ void dc_commit_updates_for_stream(struct
 		}
 	}
 
+	/* Legacy optimization path for DCE. */
+	if (update_type >= UPDATE_TYPE_FULL && dc_ctx->dce_version < DCE_VERSION_MAX) {
+		dc_post_update_surfaces_to_stream(dc);
+		TRACE_DCE_CLOCK_STATE(&context->bw_ctx.bw.dce);
+	}
+
 	return;
 
 }