linux-kernel - [PATCH 3.19 054/177] drm/i915: Clamp efficient frequency to valid range

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Message-Id: <20150316140815.540007332@linuxfoundation.org>
Date:	Mon, 16 Mar 2015 15:07:41 +0100
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Michael Auchter <a@...re.org>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Tom ORourke <Tom.ORourke@...el.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Tom O'Rourke <Tom.O'Rourke@...el.com>
Subject: [PATCH 3.19 054/177] drm/i915: Clamp efficient frequency to valid range

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

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

From: Tom O'Rourke <Tom.O'Rourke@...el.com>

commit 46efa4abe5712276494adbce102f46e3214632fd upstream.

The efficient frequency (RPe) should stay in the range
RPn <= RPe <= RP0.  The pcode clamps the returned value
internally on Broadwell but not on Haswell.

Fix for missing range check in
commit 93ee29203f506582cca2bcec5f05041526d9ab0a
Author: Tom O'Rourke <Tom.O'Rourke@...el.com>
Date:   Wed Nov 19 14:21:52 2014 -0800

    drm/i915: Use efficient frequency for HSW/BDW

Reference: http://lists.freedesktop.org/archives/intel-gfx/2015-February/059802.html
Reported-by: Michael Auchter <a@...re.org>
Suggested-by: Chris Wilson <chris@...is-wilson.co.uk>
Signed-off-by: Tom O'Rourke <Tom.O'Rourke@...el.com>
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/i915/intel_pm.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4625,7 +4625,10 @@ static void gen6_init_rps_frequencies(st
 					&ddcc_status);
 		if (0 == ret)
 			dev_priv->rps.efficient_freq =
-				(ddcc_status >> 8) & 0xff;
+				clamp_t(u8,
+					((ddcc_status >> 8) & 0xff),
+					dev_priv->rps.min_freq,
+					dev_priv->rps.max_freq);
 	}
 
 	/* Preserve min/max settings in case of re-init */


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