linux-kernel - [PATCH v2] intel_pstate: Use LFM bus ratio as min ratio/P state

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Message-Id: <1392834925-21648-1-git-send-email-dirk.j.brandewie@intel.com>
Date:	Wed, 19 Feb 2014 10:35:25 -0800
From:	dirk.brandewie@...il.com
To:	rjw@...ysocki.net
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Dirk Brandewie <dirk.j.brandewie@...el.com>
Subject: [PATCH v2] intel_pstate: Use LFM bus ratio as min ratio/P state

From: Dirk Brandewie <dirk.j.brandewie@...el.com>

LFM (max efficiency ratio) is the max frequency at minimum voltage
supported by the processor.  Using LFM as the minimum P state
increases performmance without affecting power. By not using P states
below LFM we avoid using P states that are less power efficient.

Signed-off-by: Dirk Brandewie <dirk.j.brandewie@...el.com>
---
 drivers/cpufreq/intel_pstate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index b80c03d..ff45ce1 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -356,7 +356,7 @@ static int byt_get_min_pstate(void)
 {
 	u64 value;
 	rdmsrl(BYT_RATIOS, value);
-	return value & 0xFF;
+	return (value >> 8) & 0xFF;
 }
 
 static int byt_get_max_pstate(void)
-- 
1.8.3.1

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