[PATCH 4.9 27/58] drm/bridge: tc358767: reject modes which require too much BW

From: Greg Kroah-Hartman
Date: Mon Feb 18 2019 - 08:59:41 EST


4.9-stable review patch. If anyone has any objections, please let me know.

------------------

[ 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@xxxxxx>
Reviewed-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20190103115954.12785-6-tomi.valkeinen@xxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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