linux-kernel - [ 156/167] [PATCH] drm/i915: disable sdvo hotplug on i945g/gm

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Message-Id: <20120509055051.115608089@decadent.org.uk>
Date:	Wed, 09 May 2012 06:53:05 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Daniel Vetter <daniel.vetter@...ll.ch>,
	Chris Wilson <chris@...is-wilson.co.uk>
Subject: [ 156/167] [PATCH] drm/i915: disable sdvo hotplug on i945g/gm

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

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

From: Daniel Vetter <daniel.vetter@...ll.ch>

commit 768b107e4b3be0acf6f58e914afe4f337c00932b upstream.

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.

Note that this is a regression that has been introduced in 3.1,
when we've enabled sdvo hotplug support with

commit cc68c81aed7d892deaf12d720d5455208e94cd0a
Author: Simon Farnsworth <simon.farnsworth@...lan.co.uk>
Date:   Wed Sep 21 17:13:30 2011 +0100

    drm/i915: Enable SDVO hotplug interrupts for HDMI and DVI

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=38442
Reported-and-tested-by: Dominik Köppl <dominik@...work.org>
Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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 232d77d..ae5e748 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -1220,8 +1220,14 @@ 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



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