drm/bridge: tc358767: reject modes which require too much BW

BugLink: https://bugs.launchpad.net/bugs/1837813
[ 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>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
index 24bb6bfa36f3459e316529ff9544e990bf1d6151..792a2548d3bb51708e34958c3cca42e80aad94d3 100644 (file)
--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -1112,10 +1112,20 @@ 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;
 }