linux-kernel - [PATCH v2 4/9] drm/bridge: ti-sn65dsi86: Config number of DP lanes Mo' Betta

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Date:   Tue, 17 Dec 2019 16:47:36 -0800
From:   Douglas Anderson <dianders@...omium.org>
To:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>
Cc:     robdclark@...omium.org, linux-arm-msm@...r.kernel.org,
        bjorn.andersson@...aro.org, seanpaul@...omium.org,
        Jeffrey Hugo <jeffrey.l.hugo@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Douglas Anderson <dianders@...omium.org>,
        Rob Clark <robdclark@...il.com>,
        Jonas Karlman <jonas@...boo.se>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>
Subject: [PATCH v2 4/9] drm/bridge: ti-sn65dsi86: Config number of DP lanes Mo' Betta

The driver used to say that the value to program into bridge register
0x93 was dp_lanes - 1.  Looking at the datasheet for the bridge, this
is wrong.  The data sheet says:
* 1 = 1 lane
* 2 = 2 lanes
* 3 = 4 lanes

A more proper way to express this encoding is min(dp_lanes, 3).

At the moment this change has zero effect because we've hardcoded the
number of DP lanes to 4.  ...and (4 - 1) == min(4, 3).  How fortunate!
...but soon we'll stop hardcoding the number of lanes.

Signed-off-by: Douglas Anderson <dianders@...omium.org>
Tested-by: Rob Clark <robdclark@...il.com>
Reviewed-by: Rob Clark <robdclark@...il.com>
---

Changes in v2: None

 drivers/gpu/drm/bridge/ti-sn65dsi86.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index ab644baaf90c..d55d19759796 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -523,7 +523,7 @@ static void ti_sn_bridge_enable(struct drm_bridge *bridge)
 			   CHA_DSI_LANES_MASK, val);
 
 	/* DP lane config */
-	val = DP_NUM_LANES(pdata->dp_lanes - 1);
+	val = DP_NUM_LANES(min(pdata->dp_lanes, 3));
 	regmap_update_bits(pdata->regmap, SN_SSC_CONFIG_REG, DP_NUM_LANES_MASK,
 			   val);
 
-- 
2.24.1.735.g03f4e72817-goog