linux-kernel - [PATCH] drm/msm/dsi: skip the wait for video mode done if not applicable

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Message-ID: <20230915183010.32077-1-quic_abhinavk@quicinc.com>
Date:   Fri, 15 Sep 2023 11:30:10 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     <freedreno@...ts.freedesktop.org>, 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>, Hai Li <hali@...eaurora.org>
CC:     <dri-devel@...ts.freedesktop.org>, <quic_jesszhan@...cinc.com>,
        <quic_parellan@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] drm/msm/dsi: skip the wait for video mode done if not applicable

dsi_wait4video_done() API wait for the DSI video mode engine to
become idle so that we can transmit the DCS commands in the
beginning of BLLP. However, with the current sequence, the MDP
timing engine is turned on after the panel's pre_enable() callback
which can send out the DCS commands needed to power up the panel.

During those cases, this API will always timeout and print out the
error spam leading to long bootup times and log flooding.

Fix this by checking if the DSI video engine was actually busy before
waiting for it to become idle otherwise this is a redundant wait.

Fixes: a689554ba6ed ("drm/msm: Initial add DSI connector support")
Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 0c4ec0530efc..31495e423c56 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -1075,9 +1075,21 @@ static void dsi_wait4video_done(struct msm_dsi_host *msm_host)
 
 static void dsi_wait4video_eng_busy(struct msm_dsi_host *msm_host)
 {
+	u32 data;
+
+	data = dsi_read(msm_host, REG_DSI_STATUS0);
+
 	if (!(msm_host->mode_flags & MIPI_DSI_MODE_VIDEO))
 		return;
 
+	/* if video mode engine is not busy, its because
+	 * either timing engine was not turned on or the
+	 * DSI controller has finished transmitting the video
+	 * data already, so no need to wait in those cases
+	 */
+	if (!(data & DSI_STATUS0_VIDEO_MODE_ENGINE_BUSY))
+		return;
+
 	if (msm_host->power_on && msm_host->enabled) {
 		dsi_wait4video_done(msm_host);
 		/* delay 4 ms to skip BLLP */
-- 
2.40.1