linux-kernel - [PATCH 3.19.y-ckt 112/155] drm/i915: Restore lost DPLL register write on gen2-4

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Message-Id: <1447370309-357-113-git-send-email-kamal@canonical.com>
Date:	Thu, 12 Nov 2015 15:17:46 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Nick Bowler <nbowler@...conx.ca>,
	Ville Syrjälä 
	<ville.syrjala@...ux.intel.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 112/155] drm/i915: Restore lost DPLL register write on gen2-4

3.19.8-ckt10 -stable review patch.  If anyone has any objections, please let me know.

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

From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= <ville.syrjala@...ux.intel.com>

commit 8e7a65aa70bcc1235a44e40ae0da5056525fe081 upstream.

We accidentally lost the initial DPLL register write in
1c4e02746147 drm/i915: Fix DVO 2x clock enable on 830M

The "three times for luck" hack probably saved us from a total
disaster. But anyway, bring the initial write back so that the
code actually makes some sense.

Reported-and-tested-by: Nick Bowler <nbowler@...conx.ca>
References: http://mid.gmane.org/CAN_QmVyMaArxYgEcVVsGvsMo7-6ohZr8HmF5VhkkL4i9KOmrhw@mail.gmail.com
Cc: Nick Bowler <nbowler@...conx.ca>
Signed-off-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/gpu/drm/i915/intel_display.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index ada0210..a67dde0 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1623,6 +1623,8 @@ static void i9xx_enable_pll(struct intel_crtc *crtc)
 			   I915_READ(DPLL(!crtc->pipe)) | DPLL_DVO_2X_MODE);
 	}
 
+	I915_WRITE(reg, dpll);
+
 	/* Wait for the clocks to stabilize. */
 	POSTING_READ(reg);
 	udelay(150);
-- 
1.9.1

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