linux-kernel - [PATCH v2] drm/msm/dsi: Enable BURST_MODE for command mode for DSI 6G v1.3+

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Date:   Tue, 27 Jun 2023 13:31:45 -0700
From:   Jessica Zhang <quic_jesszhan@...cinc.com>
To:     Rob Clark <robdclark@...il.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>
CC:     <quic_abhinavk@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>
Subject: [PATCH v2] drm/msm/dsi: Enable BURST_MODE for command mode for DSI
 6G v1.3+

During a frame transfer in command mode, there could be frequent
LP11 <-> HS transitions when multiple DCS commands are sent mid-frame or
if the DSI controller is running on slow clock and is throttled. To
minimize frame latency due to these transitions, it is recommended to
send the frame in a single burst.

This feature is supported for DSI 6G 1.3 and above, thus enable burst
mode if supported.

Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
---
Changes in v2:
- Moved MDP_CTRL2 register setting to dsi_ctrl_config() (Dmitry/Marijn)
- Read previous value of MDP_CTRL2 register before writing to it
  (Dmitry)
- Link to v1: https://lore.kernel.org/r/20230608-b4-add-burst-mode-v1-1-55dfbcfada55@quicinc.com
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 3f6dfb4f9d5a..cdb404885f3c 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -752,6 +752,13 @@ static void dsi_ctrl_enable(struct msm_dsi_host *msm_host,
 		/* Always insert DCS command */
 		data |= DSI_CMD_CFG1_INSERT_DCS_COMMAND;
 		dsi_write(msm_host, REG_DSI_CMD_CFG1, data);
+
+		if (msm_host->cfg_hnd->major == MSM_DSI_VER_MAJOR_6G &&
+				msm_host->cfg_hnd->minor >= MSM_DSI_6G_VER_MINOR_V1_3) {
+			data = dsi_read(msm_host, REG_DSI_CMD_MODE_MDP_CTRL2);
+			data |= DSI_CMD_MODE_MDP_CTRL2_BURST_MODE;
+			dsi_write(msm_host, REG_DSI_CMD_MODE_MDP_CTRL2, data);
+		}
 	}
 
 	dsi_write(msm_host, REG_DSI_CMD_DMA_CTRL,

---
base-commit: a0364260213c96f6817f7e85cdce293cb743460f
change-id: 20230608-b4-add-burst-mode-a5bb144069fa

Best regards,
-- 
Jessica Zhang <quic_jesszhan@...cinc.com>