[PATCH 10/11] video: rockchip: edp: Limit the lane count to four

[Ana Bobillo <anabobillo3@gmail.com>]

From: Ana Bobillo <anabobillo3@gmail.com>

rk_edp_init_training() takes the lane count from the sink's
MAX_LANE_COUNT DPCD register, masked to 5 bits, and link training uses
it to index the four ln_link_trn_ctl[] registers, the four-entry
train_set[] and the link status read from the sink. A sink reporting
more than four lanes makes rk_edp_set_link_training() write past those
registers into the ones after them, and the training loops read past
train_set[] and the link status buffer.

Limit the lane count to the four lanes the controller has, as the
analogix_dp driver in Linux does.

Fixes: 5852d539eab0 ("rockchip: video: Add a display driver for rockchip eDP")
Signed-off-by: Ana Bobillo <anabobillo3@gmail.com>
---
 drivers/video/rockchip/rk_edp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/video/rockchip/rk_edp.c b/drivers/video/rockchip/rk_edp.c
index 0ba68dbce3d..85c201e8809 100644
--- a/drivers/video/rockchip/rk_edp.c
+++ b/drivers/video/rockchip/rk_edp.c
@@ -646,6 +646,10 @@ static int rk_edp_init_training(struct rk_edp_priv *edp)
 		return -EPERM;
 	}
 
+	/* The sink may report more lanes than the controller has */
+	if (edp->link_train.lane_count > LANE_CNT4)
+		edp->link_train.lane_count = LANE_CNT4;
+
 	ret = rk_edp_link_power_up(edp);
 	if (ret)
 		return ret;