linux-kernel - [PATCH v2 4/6] drm/msm/dsi: add a comment to explain pkt_per

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Message-Id: <20231114225857.19702-5-jonathan@marek.ca>
Date:   Tue, 14 Nov 2023 17:58:32 -0500
From:   Jonathan Marek <jonathan@...ek.ca>
To:     freedreno@...ts.freedesktop.org
Cc:     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>,
        Daniel Vetter <daniel@...ll.ch>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Jiasheng Jiang <jiasheng@...as.ac.cn>,
        linux-arm-msm@...r.kernel.org (open list:DRM DRIVER FOR MSM ADRENO GPU),
        dri-devel@...ts.freedesktop.org (open list:DRM DRIVER FOR MSM ADRENO
        GPU), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 4/6] drm/msm/dsi: add a comment to explain pkt_per_line encoding

Make it clear why the pkt_per_line value is being "divided by 2".

Signed-off-by: Jonathan Marek <jonathan@...ek.ca>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 66f198e21a7e..842765063b1b 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -877,6 +877,8 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod
 	/* DSI_VIDEO_COMPRESSION_MODE & DSI_COMMAND_COMPRESSION_MODE
 	 * registers have similar offsets, so for below common code use
 	 * DSI_VIDEO_COMPRESSION_MODE_XXXX for setting bits
+	 *
+	 * pkt_per_line is log2 encoded, >>1 works for supported values (1,2,4)
 	 */
 	reg |= DSI_VIDEO_COMPRESSION_MODE_CTRL_PKT_PER_LINE(pkt_per_line >> 1);
 	reg |= DSI_VIDEO_COMPRESSION_MODE_CTRL_EOL_BYTE_NUM(eol_byte_num);
-- 
2.26.1