linux-kernel - Re: acpi_idle: Very idle Core i7 machine never enters C3

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Message-id: <alpine.LFD.2.00.1002051238280.4050@localhost.localdomain>
Date:	Fri, 05 Feb 2010 12:45:21 -0500 (EST)
From:	Len Brown <lenb@...nel.org>
To:	Jeff Garrett <jeff@...rrett.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: acpi_idle: Very idle Core i7 machine never enters C3

Jeff,
What do you see if you apply just the patch below?

Also, in addition to "powertop -d" to show what the kernel requests,
please run turbostat to show what the hardware actually did:

http://userweb.kernel.org/~lenb/acpi/utils/pmtools-latest/turbostat/turbostat.c

eg.
# turbostat -d -v sleep 5

thanks,
-Len Brown, Intel Open Source Technology Center
---

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 7c0441f..f528625 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -763,7 +763,7 @@ static const struct file_operations acpi_processor_power_fops = {
 static int acpi_idle_bm_check(void)
 {
 	u32 bm_status = 0;
-
+return bm_status;
 	acpi_read_bit_register(ACPI_BITREG_BUS_MASTER_STATUS, &bm_status);
 	if (bm_status)
 		acpi_write_bit_register(ACPI_BITREG_BUS_MASTER_STATUS, 1);

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