linux-kernel - [PATCH AUTOSEL 4.9 06/12] drm/bridge: tc358767: reject modes which require too much BW

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Message-Id: <20190209184952.127009-6-sashal@kernel.org>
Date:   Sat,  9 Feb 2019 13:49:46 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Tomi Valkeinen <tomi.valkeinen@...com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Sasha Levin <sashal@...nel.org>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 4.9 06/12] drm/bridge: tc358767: reject modes which require too much BW

From: Tomi Valkeinen <tomi.valkeinen@...com>

[ Upstream commit 51b9e62eb6950c762162ab7eb8390990179be067 ]

The current driver accepts any videomode with pclk < 154MHz. This is not
correct, as with 1 lane and/or 1.62Mbps speed not all videomodes can be
supported.

Add code to reject modes that require more bandwidth that is available.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...com>
Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
Signed-off-by: Andrzej Hajda <a.hajda@...sung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190103115954.12785-6-tomi.valkeinen@ti.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/bridge/tc358767.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
index dbe403ea130d..16fa42984c50 100644
--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -1118,10 +1118,20 @@ static bool tc_bridge_mode_fixup(struct drm_bridge *bridge,
 static int tc_connector_mode_valid(struct drm_connector *connector,
 				   struct drm_display_mode *mode)
 {
+	struct tc_data *tc = connector_to_tc(connector);
+	u32 req, avail;
+	u32 bits_per_pixel = 24;
+
 	/* DPI interface clock limitation: upto 154 MHz */
 	if (mode->clock > 154000)
 		return MODE_CLOCK_HIGH;
 
+	req = mode->clock * bits_per_pixel / 8;
+	avail = tc->link.base.num_lanes * tc->link.base.rate;
+
+	if (req > avail)
+		return MODE_BAD;
+
 	return MODE_OK;
 }
 
-- 
2.19.1