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From:   Philip Chen <philipchen@chromium.org>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     dianders@chromium.org, swboyd@chromium.org, robdclark@chromium.org,
        Philip Chen <philipchen@chromium.org>,
        Abhinav Kumar <abhinavk@codeaurora.org>,
        Bernard Zhao <bernard@vivo.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Jonathan Marek <jonathan@marek.ca>,
        Nicolas Boichat <drinkcat@chromium.org>,
        Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Yangtao Li <tiny.windzz@gmail.com>,
        dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org,
        linux-arm-msm@vger.kernel.org
Subject: [PATCH] drm/msm/dsi: set default num_data_lanes
Date:   Sat, 30 Oct 2021 10:08:50 -0700
Message-Id: <20211030100812.1.I6cd9af36b723fed277d34539d3b2ba4ca233ad2d@changeid>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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>
---

 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 c86b5090fae6..a32eb33dfc14 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;
 	}
 
-- 
2.33.1.1089.g2158813163f-goog