linux-kernel - [PATCH v13 02/12] drm/msm/dpu: decide right side per last bit

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Message-Id: <20250728-v6-16-rc2-quad-pipe-upstream-v13-2-954e4917fe4f@linaro.org>
Date: Mon, 28 Jul 2025 21:14:26 +0800
From: Jun Nie <jun.nie@...aro.org>
To: Rob Clark <robdclark@...il.com>, 
 Abhinav Kumar <quic_abhinavk@...cinc.com>, 
 Dmitry Baryshkov <lumag@...nel.org>, Sean Paul <sean@...rly.run>, 
 Marijn Suijten <marijn.suijten@...ainline.org>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Jessica Zhang <quic_jesszhan@...cinc.com>
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>, Dmitry Baryshkov <lumag@...nel.org>
Subject: [PATCH v13 02/12] drm/msm/dpu: decide right side per last bit

Currently, only one pair of mixers is supported, so a non-zero counter
value is sufficient to identify the correct mixer within that pair.
However, future implementations may involve multiple mixer pairs. With
the current implementation, all mixers within the second pair would be
incorrectly selected as right mixer. To correctly select the mixer
within a pair, test the least significant bit of the counter. If the
least significant bit is not set, select the mixer as left one;
otherwise, select the mixer as right one for all pairs.

Signed-off-by: Jun Nie <jun.nie@...aro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Reviewed-by: Jessica Zhang <quic_jesszhan@...cinc.com>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
index d4b545448d74657aafc96e9042c7756654b4f0e7..9a40492e5aa961f7180ba4ac6c86e06fcccef8c2 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
@@ -377,11 +377,10 @@ static void _dpu_crtc_setup_blend_cfg(struct dpu_crtc_mixer *mixer,
 static void _dpu_crtc_program_lm_output_roi(struct drm_crtc *crtc)
 {
 	struct dpu_crtc_state *crtc_state;
-	int lm_idx, lm_horiz_position;
+	int lm_idx;
 
 	crtc_state = to_dpu_crtc_state(crtc->state);
 
-	lm_horiz_position = 0;
 	for (lm_idx = 0; lm_idx < crtc_state->num_mixers; lm_idx++) {
 		const struct drm_rect *lm_roi = &crtc_state->lm_bounds[lm_idx];
 		struct dpu_hw_mixer *hw_lm = crtc_state->mixers[lm_idx].hw_lm;
@@ -392,7 +391,7 @@ static void _dpu_crtc_program_lm_output_roi(struct drm_crtc *crtc)
 
 		cfg.out_width = drm_rect_width(lm_roi);
 		cfg.out_height = drm_rect_height(lm_roi);
-		cfg.right_mixer = lm_horiz_position++;
+		cfg.right_mixer = lm_idx & 0x1;
 		cfg.flags = 0;
 		hw_lm->ops.setup_mixer_out(hw_lm, &cfg);
 	}

-- 
2.34.1