linux-kernel - [PATCH v9 04/14] drm/msm/dpu: decide right side per last bit

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Message-Id: <20250506-quad-pipe-upstream-v9-4-f7b273a8cc80@linaro.org>
Date: Tue, 06 May 2025 23:47:34 +0800
From: Jun Nie <jun.nie@...aro.org>
To: Rob Clark <robdclark@...il.com>, 
 Abhinav Kumar <quic_abhinavk@...cinc.com>, 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>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 Dmitry Baryshkov <lumag@...nel.org>, Dmitry Baryshkov <lumag@...nel.org>
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 v9 04/14] 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 0714936d883523e5c53bfb42f932234db76c58db..b0ee89ed7053f940d01bb55a8ea8de8ec5bc3462 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
@@ -369,11 +369,10 @@ 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;
@@ -384,7 +383,7 @@ 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