[Intel-gfx] [PATCH] drm/i915: Use the DVI clock limit in DVI mode

[Stéphane Marchesin]

When using HDMI, the 300MHz clock is legal, but when in DVI mode it's
definitely not. This causes issues when we send a 300MHz signal over a
DVI cable which is specced for 165MHz only. So when in DVI mode let's
limit the clock to 165MHz.

Signed-off-by: Stéphane Marchesin <marcheu at chromium.org>
---
 drivers/gpu/drm/i915/intel_hdmi.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index dd4fa35..0ac69f1 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -806,6 +806,10 @@ static int hdmi_portclock_limit(struct intel_hdmi *hdmi)
 {
 	struct drm_device *dev = intel_hdmi_to_dev(hdmi);
 
+	/* If we are in DVI mode, the limit is 165MHz */
+	if (!hdmi->has_hdmi_sink)
+		return 165000;
+
 	if (IS_G4X(dev))
 		return 165000;
 	else if (IS_HASWELL(dev))
-- 
1.9.1.423.g4596e3a