From 5d76b6f6c17572e662f5c99c2023adae92100855 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Tue, 19 Jan 2010 22:41:14 -0500 Subject: ACPI: enable C2 and Turbo-mode on Nehalem notebooks on A/C Linux has always ignored ACPI BIOS C2 with exit latency > 100 usec, and the ACPI spec is clear that is correct FADT-supplied C2. However, the ACPI spec explicitly states that _CST-supplied C-states have no latency limits. So move the 100usec C2 test out of the code shared by FADT and _CST code-paths, and into the FADT-specific path. This bug has not been visible until Nehalem, which advertises a CPU-C2 worst case exit latency on servers of 205usec. That (incorrect) figure is being used by BIOS writers on mobile Nehalem systems for the AC configuration. Thus, Linux ignores C2 leaving just C1, which is saves less power, and also impacts performance by preventing the use of turbo mode. http://bugzilla.kernel.org/show_bug.cgi?id=15064 Tested-by: Alex Chiang Signed-off-by: Len Brown --- drivers/acpi/processor_idle.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) (limited to 'drivers/acpi') diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index d1676b1754d..8f6da9acc8e 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -305,6 +305,17 @@ static int acpi_processor_get_power_info_fadt(struct acpi_processor *pr) pr->power.states[ACPI_STATE_C2].latency = acpi_gbl_FADT.C2latency; pr->power.states[ACPI_STATE_C3].latency = acpi_gbl_FADT.C3latency; + /* + * FADT specified C2 latency must be less than or equal to + * 100 microseconds. + */ + if (acpi_gbl_FADT.C2latency > ACPI_PROCESSOR_MAX_C2_LATENCY) { + ACPI_DEBUG_PRINT((ACPI_DB_INFO, + "C2 latency too large [%d]\n", acpi_gbl_FADT.C2latency)); + /* invalidate C2 */ + pr->power.states[ACPI_STATE_C2].address = 0; + } + ACPI_DEBUG_PRINT((ACPI_DB_INFO, "lvl2[0x%08x] lvl3[0x%08x]\n", pr->power.states[ACPI_STATE_C2].address, @@ -500,16 +511,6 @@ static void acpi_processor_power_verify_c2(struct acpi_processor_cx *cx) if (!cx->address) return; - /* - * C2 latency must be less than or equal to 100 - * microseconds. - */ - else if (cx->latency > ACPI_PROCESSOR_MAX_C2_LATENCY) { - ACPI_DEBUG_PRINT((ACPI_DB_INFO, - "latency too large [%d]\n", cx->latency)); - return; - } - /* * Otherwise we've met all of our C2 requirements. * Normalize the C2 latency to expidite policy -- cgit v1.2.3-70-g09d2 From a6d72c189f6c4292ba1a323e8af24083790529f8 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Tue, 19 Jan 2010 23:10:04 -0500 Subject: ACPI: allow C3 > 1000usec Do for C3 what the previous patch did for C2. The C2 patch was in response to a highly visible and multiply reported C-state/turbo failure, while this change has no bug report in-hand. This will enable C3 in Linux on systems where BIOS overstates C3 latency in _CST. It will also enable future systems which may actually have C3 > 1000usec. Linux has always ignored ACPI BIOS C3 with exit latency > 1000 usec, and the ACPI spec is clear that is correct FADT-supplied C3. However, the ACPI spec explicitly states that _CST-supplied C-states have no latency limits. So move the 1000usec C3 test out of the code shared by FADT and _CST code-paths, and into the FADT-specific path. Signed-off-by: Len Brown --- drivers/acpi/processor_idle.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) (limited to 'drivers/acpi') diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 8f6da9acc8e..2c543b42eb1 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -316,6 +316,17 @@ static int acpi_processor_get_power_info_fadt(struct acpi_processor *pr) pr->power.states[ACPI_STATE_C2].address = 0; } + /* + * FADT supplied C3 latency must be less than or equal to + * 1000 microseconds. + */ + if (acpi_gbl_FADT.C3latency > ACPI_PROCESSOR_MAX_C3_LATENCY) { + ACPI_DEBUG_PRINT((ACPI_DB_INFO, + "C3 latency too large [%d]\n", acpi_gbl_FADT.C3latency)); + /* invalidate C3 */ + pr->power.states[ACPI_STATE_C3].address = 0; + } + ACPI_DEBUG_PRINT((ACPI_DB_INFO, "lvl2[0x%08x] lvl3[0x%08x]\n", pr->power.states[ACPI_STATE_C2].address, @@ -532,16 +543,6 @@ static void acpi_processor_power_verify_c3(struct acpi_processor *pr, if (!cx->address) return; - /* - * C3 latency must be less than or equal to 1000 - * microseconds. - */ - else if (cx->latency > ACPI_PROCESSOR_MAX_C3_LATENCY) { - ACPI_DEBUG_PRINT((ACPI_DB_INFO, - "latency too large [%d]\n", cx->latency)); - return; - } - /* * PIIX4 Erratum #18: We don't support C3 when Type-F (fast) * DMA transfers are used by any ISA device to avoid livelock. -- cgit v1.2.3-70-g09d2 From d22edd293ff3f1e2d252f164fe2cf744620cb660 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Tue, 19 Jan 2010 23:29:09 -0500 Subject: ACPI: delete acpi_processor_power_verify_c2() no functional change -- cleanup only. acpi_processor_power_verify_c2() was nearly empty due to a previous patch, so expand its remains into its one caller and delete it. Signed-off-by: Len Brown --- drivers/acpi/processor_idle.c | 22 ++++------------------ 1 file changed, 4 insertions(+), 18 deletions(-) (limited to 'drivers/acpi') diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 2c543b42eb1..7c0441f63b3 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -516,23 +516,6 @@ static int acpi_processor_get_power_info_cst(struct acpi_processor *pr) return status; } -static void acpi_processor_power_verify_c2(struct acpi_processor_cx *cx) -{ - - if (!cx->address) - return; - - /* - * Otherwise we've met all of our C2 requirements. - * Normalize the C2 latency to expidite policy - */ - cx->valid = 1; - - cx->latency_ticks = cx->latency; - - return; -} - static void acpi_processor_power_verify_c3(struct acpi_processor *pr, struct acpi_processor_cx *cx) { @@ -631,7 +614,10 @@ static int acpi_processor_power_verify(struct acpi_processor *pr) break; case ACPI_STATE_C2: - acpi_processor_power_verify_c2(cx); + if (!cx->address) + break; + cx->valid = 1; + cx->latency_ticks = cx->latency; /* Normalize latency */ break; case ACPI_STATE_C3: -- cgit v1.2.3-70-g09d2