linux-kernel - [PATCH] powernow-k8: Limit Pstate transition latency check

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Message-ID: <20100708155530.GA5301@aftab>
Date:	Thu, 8 Jul 2010 17:55:30 +0200
From:	Borislav Petkov <borislav.petkov@....com>
To:	Dave Jones <davej@...hat.com>
CC:	Mark Langsdorf <Mark.Langsdorf@....com>,
	Thomas Renninger <trenn@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	<cpufreq@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] powernow-k8: Limit Pstate transition latency check

The Pstate transition latency check was added for broken F10h BIOSen
which wrongly contain a value of 0 for transition and bus master
latency. Fam11h and later, however, (will) have similar transition
latency so extend that behavior for them too.

Signed-off-by: Borislav Petkov <borislav.petkov@....com>
---
 arch/x86/kernel/cpu/cpufreq/powernow-k8.c |   11 +++++------
 1 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
index 7ec2123..3e90cce 100644
--- a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
+++ b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
@@ -1023,13 +1023,12 @@ static int get_transition_latency(struct powernow_k8_data *data)
 	}
 	if (max_latency == 0) {
 		/*
-		 * Fam 11h always returns 0 as transition latency.
-		 * This is intended and means "very fast". While cpufreq core
-		 * and governors currently can handle that gracefully, better
-		 * set it to 1 to avoid problems in the future.
-		 * For all others it's a BIOS bug.
+		 * Fam 11h and later may return 0 as transition latency. This
+		 * is intended and means "very fast". While cpufreq core and
+		 * governors currently can handle that gracefully, better set it
+		 * to 1 to avoid problems in the future.
 		 */
-		if (boot_cpu_data.x86 != 0x11)
+		if (boot_cpu_data.x86 < 0x11)
 			printk(KERN_ERR FW_WARN PFX "Invalid zero transition "
 				"latency\n");
 		max_latency = 1;
-- 
1.7.1


-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632

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