From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Philip Chen <philipchen@chromium.org>,
        Douglas Anderson <dianders@chromium.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Rob Clark <robdclark@chromium.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 21/42] drm/msm/dsi: set default num_data_lanes
Date:   Wed, 15 Dec 2021 18:21:02 +0100
Message-Id: <20211215172027.398099966@linuxfoundation.org>
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From: Philip Chen <philipchen@chromium.org>

[ Upstream commit cd92cc187c053ab010a1570e2d61d68394a5c725 ]

If "data_lanes" property of the dsi output endpoint is missing in
the DT, num_data_lanes would be 0 by default, which could cause
dsi_host_attach() to fail if dsi->lanes is set to a non-zero value
by the bridge driver.

According to the binding document of msm dsi controller, the
input/output endpoint of the controller is expected to have 4 lanes.
So let's set num_data_lanes to 4 by default.

Signed-off-by: Philip Chen <philipchen@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20211030100812.1.I6cd9af36b723fed277d34539d3b2ba4ca233ad2d@changeid
Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 ea641151e77e7..dc85974c78975 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -1696,6 +1696,8 @@ static int dsi_host_parse_lane_data(struct msm_dsi_host *msm_host,
 	if (!prop) {
 		DRM_DEV_DEBUG(dev,
 			"failed to find data lane mapping, using default\n");
+		/* Set the number of date lanes to 4 by default. */
+		msm_host->num_data_lanes = 4;
 		return 0;
 	}
 
-- 
2.33.0