[Intel-gfx] [PATCH] drm/i915: disable sdvo hotplug on i945g/gm

[Daniel Vetter]

Chris Wilson dug out a hw erratum saying that there's noise on the
interrupt line on i945G chips. We also have a bug report from a i945GM
chip with an sdvo hotplug interrupt storm (and no apparent cause).

Play it safe and disable sdvo hotplug on all i945 variants.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=38442
Reported-and-tested-by: Dominik Köppl <dominik at devwork.org>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/intel_sdvo.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index c330efd..bf6be6c 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -1232,8 +1232,14 @@ static bool intel_sdvo_get_capabilities(struct intel_sdvo *intel_sdvo, struct in
 
 static int intel_sdvo_supports_hotplug(struct intel_sdvo *intel_sdvo)
 {
+	struct drm_device *dev = intel_sdvo->base.base.dev;
 	u8 response[2];
 
+	/* HW Erratum: SDVO Hotplug is broken on all i945G chips, there's noise
+	 * on the line. */
+	if (IS_I945G(dev) || IS_I945GM(dev))
+		return false;
+
 	return intel_sdvo_get_value(intel_sdvo, SDVO_CMD_GET_HOT_PLUG_SUPPORT,
 				    &response, 2) && response[0];
 }
-- 
1.7.10