linux-kernel - [PATCH v4 06/16] drm/msm/dpu: fix mixer number counter on allocation

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Message-Id: <20250116-sm8650-v6-13-hmd-deckard-mdss-quad-upstream-33-v4-6-74749c6eba33@linaro.org>
Date: Thu, 16 Jan 2025 15:25:55 +0800
From: Jun Nie <jun.nie@...aro.org>
To: Rob Clark <robdclark@...il.com>, 
 Abhinav Kumar <quic_abhinavk@...cinc.com>, 
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, Sean Paul <sean@...rly.run>, 
 Marijn Suijten <marijn.suijten@...ainline.org>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Jun Nie <jun.nie@...aro.org>
Subject: [PATCH v4 06/16] drm/msm/dpu: fix mixer number counter on
 allocation

Add the case to reserve multiple pairs mixers for high resolution.
Current code only supports one pair of mixer usage case. To support
quad-pipe usage case, two pairs of mixers are needed.

Reset the current lm_count to an even number instead of completely
clearing it. This prevents all pairs from being cleared in cases
where multiple LM pairs are needed.

Signed-off-by: Jun Nie <jun.nie@...aro.org>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
index 24e085437039e..3b3660d0b166d 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
@@ -321,7 +321,11 @@ static int _dpu_rm_reserve_lms(struct dpu_rm *rm,
 		if (!rm->mixer_blks[i])
 			continue;
 
-		lm_count = 0;
+		/*
+		 * Reset lm_count to an even index. This will drop the previous
+		 * primary mixer if failed to find its peer.
+		 */
+		lm_count &= ~1;
 		lm_idx[lm_count] = i;
 
 		if (!_dpu_rm_check_lm_and_get_connected_blks(rm, global_state,

-- 
2.34.1