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linux/drivers/acpi
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Dave Hansen 02e61196c5 ACPI: processor idle: Practically limit "Dummy wait" workaround to old Intel systems 
commit e400ad8b7e upstream.

Old, circa 2002 chipsets have a bug: they don't go idle when they are
supposed to.  So, a workaround was added to slow the CPU down and
ensure that the CPU waits a bit for the chipset to actually go idle.
This workaround is ancient and has been in place in some form since
the original kernel ACPI implementation.

But, this workaround is very painful on modern systems.  The "inl()"
can take thousands of cycles (see Link: for some more detailed
numbers and some fun kernel archaeology).

First and foremost, modern systems should not be using this code.
Typical Intel systems have not used it in over a decade because it is
horribly inferior to MWAIT-based idle.

Despite this, people do seem to be tripping over this workaround on
AMD system today.

Limit the "dummy wait" workaround to Intel systems.  Keep Modern AMD
systems from tripping over the workaround.  Remotely modern Intel
systems use intel_idle instead of this code and will, in practice,
remain unaffected by the dummy wait.

Reported-by: K Prateek Nayak <kprateek.nayak@amd.com>
Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://lore.kernel.org/all/20220921063638.2489-1-kprateek.nayak@amd.com/
Link: https://lkml.kernel.org/r/20220922184745.3252932-1-dave.hansen@intel.com
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-02-06 07:59:01 +01:00
..
acpica ACPICA: Fix error code path in acpi_ds_call_control_method() 2022-12-31 13:14:40 +01:00
apei ACPI: APEI: Fix integer overflow in ghes_estatus_pool_init() 2022-11-10 18:15:34 +01:00
arm64 ACPI/IORT: Check node revision for PMCG resources 2022-02-16 12:56:19 +01:00
dptf ACPI: DPTF: Add new PCH FIVR methods 2021-08-04 18:08:50 +02:00
nfit ACPI: NFIT: Use fallback node id when numa info in NFIT table is incorrect 2021-09-27 11:40:43 -07:00
numa ACPI: HMAT: Fix initiator registration for single-initiator systems 2022-12-08 11:28:45 +01:00
pmic ACPI: PMIC: Fix intel_pmic_regs_handler() read accesses 2021-11-18 19:17:06 +01:00
x86 Revert "ACPI: PM: Add support for upcoming AMD uPEP HID AMDI007" 2023-01-12 11:59:19 +01:00
ac.c ACPI: AC: Quirk GK45 to skip reading _PSR 2021-11-18 19:16:19 +01:00
acpi_adxl.c ACPI/ADXL: Add address translation interface using an ACPI DSM 2018-10-16 10:03:00 +02:00
acpi_amba.c ACPI: AMBA: Fix resource name in /proc/iomem 2021-06-30 20:01:10 +02:00
acpi_apd.c serial: 8250_dw: Add device HID for new AMD UART controller 2021-05-13 17:08:42 +02:00
acpi_cmos_rtc.c ACPI: cmos_rtc: Using pr_fmt() and remove PREFIX 2021-06-07 15:36:45 +02:00
acpi_configfs.c ACPI: configfs: Make get_header() to return error pointer 2021-07-16 19:20:28 +02:00
acpi_dbg.c ACPI: debug: Remove the not used function 2020-11-17 18:12:34 +01:00
acpi_extlog.c ACPI: extlog: Handle multiple records 2022-10-29 10:12:55 +02:00
acpi_fpdt.c ACPI: tables: FPDT: Don't call acpi_os_map_memory() on invalid phys address 2022-10-26 12:35:30 +02:00
acpi_ipmi.c ACPI: ipmi: Remove address space handler in error path 2021-05-24 16:27:34 +02:00
acpi_lpat.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
acpi_lpit.c ACPI: LPIT: Put the low power idle table after using it 2020-05-09 11:29:16 +02:00
acpi_lpss.c ACPI: LPSS: Fix missing check in register_device_clock() 2022-08-17 14:23:03 +02:00
acpi_memhotplug.c ACPI: memhotplug: use a single static memory group for a single memory device 2021-09-08 11:50:23 -07:00
acpi_pad.c ACPI: processor: Replace deprecated CPU-hotplug functions 2021-08-04 20:25:54 +02:00
acpi_platform.c ACPI: platform: Remove ACPI_MODULE_NAME() 2020-09-25 18:25:51 +02:00
acpi_pnp.c ACPI: PNP: compare the string length in the matching_id() 2020-12-15 19:30:49 +01:00
acpi_processor.c ACPI: processor: Replace deprecated CPU-hotplug functions 2021-08-04 20:25:54 +02:00
acpi_tad.c ACPI: Use DEVICE_ATTR_<RW|RO|WO> macros 2021-01-22 16:17:19 +01:00
acpi_video.c ACPI: video: Add Toshiba Satellite/Portege Z830 quirk 2022-10-26 12:35:30 +02:00
acpi_watchdog.c ACPI: watchdog: Replace open coded variant of resource_union() 2020-11-17 18:06:29 +01:00
battery.c ACPI: battery: Add device HID and quirk for Microsoft Surface Go 3 2022-03-28 09:58:44 +02:00
bgrt.c ACPI: bgrt: Use sysfs_emit 2021-06-23 19:27:50 +02:00
blacklist.c ACPI: blacklist: Unify the message printing 2021-06-07 15:36:45 +02:00
bus.c ACPI: VIOT: Fix ACS setup 2022-08-17 14:23:11 +02:00
button.c ACPI: button: Add DMI quirk for Lenovo Yoga 9 (14INTL5) 2021-08-25 19:57:01 +02:00
container.c ACPI: container: Remove leftover ACPICA debug functionality 2020-09-25 18:25:51 +02:00
cppc_acpi.c ACPI: CPPC: Do not prevent CPPC from working in the future 2022-08-17 14:24:25 +02:00
custom_method.c ACPI: custom_method: fix a possible memory leak 2021-04-28 19:17:54 +02:00
debugfs.c ACPI: debugfs: Remove dead ACPICA debug code 2020-09-25 18:25:51 +02:00
device_pm.c for-5.14/drivers-2021-06-29 2021-06-30 12:21:16 -07:00
device_sysfs.c ACPI: sysfs: fix doc warnings in device_sysfs.c 2021-06-17 14:32:05 +02:00
dock.c ACPI: dock: fix some coding style issues 2021-04-08 16:27:03 +02:00
ec.c ACPI: EC: Drop the EC_FLAGS_IGNORE_DSDT_GPE quirk 2022-08-17 14:23:03 +02:00
ec_sys.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 482 2019-06-19 17:09:52 +02:00
event.c Merge branches 'acpi-ec', 'acpi-apei', 'acpi-soc' and 'acpi-misc' 2021-06-29 15:51:25 +02:00
evged.c ACPI: GED: fix -Wformat 2020-11-09 19:25:20 +01:00
fan.c ACPI: PM / fan: Put fan device IDs into separate header file 2021-05-21 19:02:35 +02:00
fan.h ACPI: PM / fan: Put fan device IDs into separate header file 2021-05-21 19:02:35 +02:00
glue.c Revert "ACPI: scan: Release PM resources blocked by unused objects" 2021-11-21 13:44:14 +01:00
hed.c ACPI: HED: Drop unused ACPI_MODULE_NAME() definition 2021-03-08 16:51:48 +01:00
internal.h ACPI: EC: Rework flushing of EC work while suspended to idle 2022-01-27 11:03:23 +01:00
ioapic.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
irq.c ACPI: irq: Prevent unregistering of GIC SGIs 2021-04-23 18:00:52 +01:00
Kconfig Merge branches 'acpi-numa', 'acpi-glue', 'acpi-config' and 'acpi-pmic' 2021-08-30 19:30:37 +02:00
Makefile IOMMU Updates for Linux v5.14 2021-07-02 13:22:47 -07:00
nvs.c Merge branches 'acpi-ec', 'acpi-apei', 'acpi-soc' and 'acpi-misc' 2021-06-29 15:51:25 +02:00
osi.c ACPI: OSI: Shoot duplicate word 2019-11-13 11:12:08 +01:00
osl.c Revert "ACPI: Add memory semantics to acpi_os_map_memory()" 2021-09-23 20:39:36 +02:00
pci_irq.c ACPI: PCI: IRQ: Consolidate printing diagnostic messages 2021-03-08 16:51:08 +01:00
pci_link.c ACPI: utils: Introduce acpi_evaluation_failure_warn() 2021-03-08 19:10:30 +01:00
pci_mcfg.c PCI/ACPI: Guard ARM64-specific mcfg_quirks 2022-08-25 11:40:36 +02:00
pci_root.c ACPI: APEI: explicit init of HEST and GHES in apci_init() 2022-08-17 14:23:11 +02:00
pci_slot.c ACPI: PCI: Remove unused ACPICA debug code 2020-09-25 18:25:51 +02:00
platform_profile.c ACPI: platform-profile: call sysfs_notify() from platform_profile_store() 2021-08-16 18:32:02 +02:00
power.c ACPI: PM: Fix device wakeup power reference counting error 2021-11-18 19:17:09 +01:00
pptt.c ACPI: tables: PPTT: Populate cache-id if provided by firmware 2021-06-07 15:55:02 +02:00
prmt.c ACPI: PRM: Check whether EFI runtime is available 2023-01-24 07:22:45 +01:00
proc.c ACPI: proc: Remove dead ACPICA debug code 2020-09-25 18:25:51 +02:00
processor_core.c ACPI: processor: Remove dead ACPICA debug code 2020-09-25 18:25:51 +02:00
processor_driver.c ACPI: processor: Get rid of ACPICA message printing 2021-03-08 16:51:19 +01:00
processor_idle.c ACPI: processor idle: Practically limit "Dummy wait" workaround to old Intel systems 2023-02-06 07:59:01 +01:00
processor_pdc.c ACPI: processor: Get rid of ACPICA message printing 2021-03-08 16:51:19 +01:00
processor_perflib.c ACPI: processor_perflib: Cleanup print messages 2021-06-07 15:36:46 +02:00
processor_thermal.c ACPI: processor: Remove freq Qos request for all CPUs 2022-08-31 17:16:48 +02:00
processor_throttling.c Merge branches 'acpi-dptf' and 'acpi-messages' 2021-06-29 15:50:37 +02:00
property.c ACPI: property: Return type of acpi_add_nondev_subnodes() should be bool 2022-08-25 11:40:10 +02:00
reboot.c ACPI: reboot: Unify the message printing 2021-06-07 15:36:46 +02:00
resource.c ACPI: resource: do IRQ override on Lenovo 14ALC7 2023-01-12 11:58:42 +01:00
sbs.c ACPI: sbs: Unify the message printing 2021-06-07 15:36:46 +02:00
sbshc.c Merge branches 'acpi-ec', 'acpi-apei', 'acpi-soc' and 'acpi-misc' 2021-06-29 15:51:25 +02:00
sbshc.h ACPI: Fix whitespace inconsistencies 2020-11-09 19:08:06 +01:00
scan.c ACPI: scan: Add LATT2021 to acpi_ignore_dep_ids[] 2022-11-26 09:24:31 +01:00
sleep.c ACPI: PM: save NVS memory for Lenovo G40-45 2022-08-17 14:23:03 +02:00
sleep.h Revert "Revert "ACPI: scan: Turn off unused power resources during initialization"" 2021-05-10 14:02:17 +02:00
spcr.c ACPI: SPCR: Add support for the new 16550-compatible Serial Port Subtype 2021-08-16 18:38:08 +02:00
sysfs.c ACPI: sysfs: Fix BERT error region memory mapping 2022-05-30 09:28:58 +02:00
tables.c memblock: exclude MEMBLOCK_NOMAP regions from kmemleak 2021-10-21 18:30:49 -10:00
thermal.c ACPI: thermal: drop an always true check 2022-09-05 10:30:03 +02:00
tiny-power-button.c ACPI: tiny-power-button: Simplify the code using module_acpi_driver() 2020-11-17 18:12:34 +01:00
utils.c ACPI: utils: Fix reference counting in for_each_acpi_dev_match() 2021-07-19 16:22:01 +02:00
video_detect.c ACPI: video: Force backlight native for more TongFang devices 2022-10-29 10:12:58 +02:00
viot.c ACPI: VIOT: Fix ACS setup 2022-08-17 14:23:11 +02:00
wakeup.c ACPI: Fix whitespace inconsistencies 2020-11-09 19:08:06 +01:00