linux-kernel - [PATCH 1/3] powernow-k8: Avoid Pstate MSR accesses on systems supporting CPB

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Date:	Fri, 6 Jan 2012 15:56:31 +0100
From:	Andreas Herrmann <andreas.herrmann3@....com>
To:	Dave Jones <davej@...hat.com>
CC:	<cpufreq@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/3] powernow-k8: Avoid Pstate MSR accesses on systems
 supporting CPB


Due to CPB we can't directly map SW Pstates to Pstate MSRs. Get rid of
the paranoia check. (assuming that the ACPI Pstate information is
correct.)

Signed-off-by: Andreas Herrmann <andreas.herrmann3@....com>
---
 drivers/cpufreq/powernow-k8.c |   19 ++++++++++---------
 1 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/cpufreq/powernow-k8.c b/drivers/cpufreq/powernow-k8.c
index bce576d..e0329f9 100644
--- a/drivers/cpufreq/powernow-k8.c
+++ b/drivers/cpufreq/powernow-k8.c
@@ -926,23 +926,24 @@ static int fill_powernow_table_pstate(struct powernow_k8_data *data,
 			invalidate_entry(powernow_table, i);
 			continue;
 		}
-		rdmsr(MSR_PSTATE_DEF_BASE + index, lo, hi);
-		if (!(hi & HW_PSTATE_VALID_MASK)) {
-			pr_debug("invalid pstate %d, ignoring\n", index);
-			invalidate_entry(powernow_table, i);
-			continue;
-		}
-
-		powernow_table[i].index = index;
-
 		/* Frequency may be rounded for these */
 		if ((boot_cpu_data.x86 == 0x10 && boot_cpu_data.x86_model < 10)
 				 || boot_cpu_data.x86 == 0x11) {
+
+			rdmsr(MSR_PSTATE_DEF_BASE + index, lo, hi);
+			if (!(hi & HW_PSTATE_VALID_MASK)) {
+				pr_debug("invalid pstate %d, ignoring\n", index);
+				invalidate_entry(powernow_table, i);
+				continue;
+			}
+
 			powernow_table[i].frequency =
 				freq_from_fid_did(lo & 0x3f, (lo >> 6) & 7);
 		} else
 			powernow_table[i].frequency =
 				data->acpi_data.states[i].core_frequency * 1000;
+
+		powernow_table[i].index = index;
 	}
 	return 0;
 }
-- 
1.7.8.1



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