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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Tomi Valkeinen <tomi.valkeinen@ti.com>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Sasha Levin <sashal@kernel.org>,
        dri-devel@lists.freedesktop.org
Subject: [PATCH AUTOSEL 4.20 19/42] drm/bridge: tc358767: reject modes which require too much BW
Date:   Sat,  9 Feb 2019 13:47:11 -0500
Message-Id: <20190209184734.125935-19-sashal@kernel.org>
In-Reply-To: <20190209184734.125935-1-sashal@kernel.org>
References: <20190209184734.125935-1-sashal@kernel.org>
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From: Tomi Valkeinen <tomi.valkeinen@ti.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@ti.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190103115954.12785-6-tomi.valkeinen@ti.com
Signed-off-by: Sasha Levin <sashal@kernel.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 ab299f4debfa..a1f3dd2afbb1 100644
--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -1114,10 +1114,20 @@ static bool tc_bridge_mode_fixup(struct drm_bridge *bridge,
 static enum drm_mode_status 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