The PCI Express Capability (PCIe spec r3.0, sec 7.8) comes in two
versions, v1 and v2. In v1 Capability structures (PCIe spec r1.0 and
r1.1), some fields are optional, so the structure size depends on the
device type.
This patch adds functions to access this capability so drivers don't
have to be aware of the differences between v1 and v2. Note that these
new functions apply only to the "PCI Express Capability," not to any of
the other "PCI Express Extended Capabilities" (AER, VC, ACS, MFVC, etc.)
Function pcie_capability_read_word/dword() reads the PCIe Capabilities
register and returns the value in the reference parameter "val". If
the PCIe Capabilities register is not implemented on the PCIe device,
"val" is set to 0.
Function pcie_capability_write_word/dword() writes the value to the
specified PCIe Capability register.
Function pcie_capability_clear_and_set_word/dword() sets and/or clears bits
of a PCIe Capability register.
[bhelgaas: changelog, drop "pci_" prefixes, don't export
pcie_capability_reg_implemented()]
Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This adds the fields in the Vendor-Specific Header: ID, Rev, and Length.
There may be multiple Vendor-Specific capabilities, so drivers should use
the VSEC ID to identify the one of interest.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Pull drm updates from Dave Airlie:
"One of the smaller drm -next pulls in ages!
Ben (nouveau) has a rewrite in progress but we decided to leave it
stew for another cycle, so just some fixes from him.
- radeon: lots of documentation work, fixes, more ring and locking
changes, pcie gen2, more dp fixes.
- i915: haswell features, gpu reset fixes, /dev/agpgart removal on
machines that we never used it on, more VGA/HDP fix., more DP fixes
- drm core: cleanups from Daniel, sis 64-bit fixes, range allocator
colouring.
but yeah fairly quiet merge this time, probably because I missed half
of it!"
Trivial add-add conflict in include/linux/pci_regs.h
* 'drm-next' of git://people.freedesktop.org/~airlied/linux: (255 commits)
drm/nouveau: init vblank requests list
drm/nv50: extend vblank semaphore to generic dmaobj + offset pair
drm/nouveau: mark most of our ioctls as deprecated, move to compat layer
drm/nouveau: move current gpuobj code out of nouveau_object.c
drm/nouveau/gem: fix object reference leak in a failure path
drm/nv50: rename INVALID_QUERY_OR_TEXTURE error to INVALID_OPERATION
drm/nv84: decode PCRYPT errors
drm/nouveau: dcb table quirk for fdo#50830
nouveau: Fix alignment requirements on src and dst addresses
drm/i915: unbreak lastclose for failed driver init
drm/i915: Set the context before setting up regs for the context.
drm/i915: constify mode in crtc_mode_fixup
drm/i915/lvds: ditch ->prepare special case
drm/i915: dereferencing an error pointer
drm/i915: fix invalid reference handling of the default ctx obj
drm/i915: Add -EIO to the list of known errors for __wait_seqno
drm/i915: Flush the context object from the CPU caches upon switching
drm/radeon: fix dpms on/off on trinity/aruba v2
drm/radeon: on hotplug force link training to happen (v2)
drm/radeon: fix hotplug of DP to DVI|HDMI passive adapters (v2)
...
We need these for detecting the max link speed for drm drivers.
Acked-by: Bjorn Helgaas <bhelgass@google.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
* pci/bjorn-p2p-bridge-windows:
sparc/PCI: replace pci_cfg_fake_ranges() with pci_read_bridge_bases()
PCI: support sizing P2P bridge I/O windows with 1K granularity
PCI: reimplement P2P bridge 1K I/O windows (Intel P64H2)
PCI: allow P2P bridge windows starting at PCI bus address zero
Conflicts:
drivers/pci/probe.c
include/linux/pci.h
9d265124d0 and 15a260d53f added quirks for P2P bridges that support
I/O windows that start/end at 1K boundaries, not just the 4K boundaries
defined by the PCI spec. For details, see the IOBL_ADR register and the
EN1K bit in the CNF register in the Intel 82870P2 (P64H2).
These quirks complicate the code that reads P2P bridge windows
(pci_read_bridge_io() and pci_cfg_fake_ranges()) because the bridge
I/O resource is updated in the HEADER quirk, in pci_read_bridge_io(),
in pci_setup_bridge(), and again in the FINAL quirk. This is confusing
and makes it impossible to reassign the bridge windows after FINAL
quirks are run.
This patch adds support for 1K windows in the generic paths, so the
HEADER quirk only has to enable this support. The FINAL quirk, which
used to undo damage done by pci_setup_bridge(), is no longer needed.
This removes "if (!res->start) res->start = ..." from pci_read_bridge_io();
that was part of 9d265124d0 to avoid overwriting the resource filled in
by the quirk. Since pci_read_bridge_io() itself now knows about
granularity, the quirk no longer updates the resource and this test is no
longer needed.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Fill in many missing definitions and add sizeof fields for many
sections allowing for more extensive config parsing.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This patch resolves potential issues when accessing PCI Express
Capability structures. The makeup of the capability varies
substantially between v1 and v2:
Version 1 of the PCI Express Capability (defined by PCI Express
1.0 and 1.1 base) neither requires the endpoint to implement the
entire PCIe capability structure nor specifies default values of
registers that are not implemented by the device.
Version 2 of the PCI Express Capability (defined by PCIe 1.1
Capability Structure Expansion ECN, PCIe 2.0, 2.1, and 3.0) added
additional registers to the structure and requires all registers
to be either implemented or hardwired to 0.
Due to the differences in the capability structures, code dealing with
capability features must be careful not to access the additional
registers introduced with v2 unless the device is specifically known to
be a v2 capable device. Otherwise, attempts to access non-existant
registers will occur. This is a subtle issue that is hard to track down
when it occurs (and it has - see commit 864d296cf9).
To try and help mitigate such occurrences, this patch introduces
pci_pcie_cap2() which is similar to pci_pcie_cap() but also checks
that the PCIe capability version is >= 2. pci_pcie_cap2() should be
used for qualifying PCIe capability features introduced after v1.
Suggested by Don Dutile.
Acked-by: Donald Dutile <ddutile@redhat.com>
Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
* 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci: (80 commits)
x86/PCI: Expand the x86_msi_ops to have a restore MSIs.
PCI: Increase resource array mask bit size in pcim_iomap_regions()
PCI: DEVICE_COUNT_RESOURCE should be equal to PCI_NUM_RESOURCES
PCI: pci_ids: add device ids for STA2X11 device (aka ConneXT)
PNP: work around Dell 1536/1546 BIOS MMCONFIG bug that breaks USB
x86/PCI: amd: factor out MMCONFIG discovery
PCI: Enable ATS at the device state restore
PCI: msi: fix imbalanced refcount of msi irq sysfs objects
PCI: kconfig: English typo in pci/pcie/Kconfig
PCI/PM/Runtime: make PCI traces quieter
PCI: remove pci_create_bus()
xtensa/PCI: convert to pci_scan_root_bus() for correct root bus resources
x86/PCI: convert to pci_create_root_bus() and pci_scan_root_bus()
x86/PCI: use pci_scan_bus() instead of pci_scan_bus_parented()
x86/PCI: read Broadcom CNB20LE host bridge info before PCI scan
sparc32, leon/PCI: convert to pci_scan_root_bus() for correct root bus resources
sparc/PCI: convert to pci_create_root_bus()
sh/PCI: convert to pci_scan_root_bus() for correct root bus resources
powerpc/PCI: convert to pci_create_root_bus()
powerpc/PCI: split PHB part out of pcibios_map_io_space()
...
Fix up conflicts in drivers/pci/msi.c and include/linux/pci_regs.h due
to the same patches being applied in other branches.
These are extended capabilities, rename and move to proper
group for consistency.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
More consistency cleanups. Drop the _OFF, separate and indent
CTRL/CAP/STATUS bit definitions. This helped find the previous
mis-use of bit 0 in the PASID capability register.
Reviewed-by: Joerg Roedel <joerg.roedel@amd.com>
Tested-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
These are extended capabilities, rename and move to proper
group for consistency.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Devices supporting Process Address Space Identifiers
(PASIDs) can use an IOMMU to access multiple IO address
spaces at the same time. A PCIe device indicates support for
this feature by implementing the PASID capability. This
patch adds support for the capability to the Linux kernel.
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Implement the necessary functions to handle PRI capabilities
on PCIe devices. With PRI devices behind an IOMMU can signal
page fault conditions to software and recover from such
faults.
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Latency tolerance reporting allows devices to send messages to the root
complex indicating their latency tolerance for snooped & unsnooped
memory transactions. Add support for enabling & disabling this
feature, along with a routine to set the max latencies a device should
send upstream.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
OBFF (optimized buffer flush/fill), where supported, can help improve
energy efficiency by giving devices information about when interrupts
and other activity will have a reduced power impact. It requires
support from both the device and system (i.e. not only does the device
need to respond to OBFF messages, but the platform must be capable of
generating and routing them to the end point).
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Add support to allow drivers to enable/disable ID-based ordering. Where
supported, ID-based ordering can significantly improve the latency of
individual requests by preventing them from queueing up behind unrelated
traffic.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
I noticed that PCI Express PMEs don't work on my Toshiba Portege R500
after the system has been woken up from a sleep state by a PME
(through Wake-on-LAN). After some investigation it turned out that
the BIOS didn't clear the Root PME Status bit in the root port that
received the wakeup PME and since the Requester ID was also set in
the port's Root Status register, any subsequent PMEs didn't trigger
interrupts.
This problem can be avoided by clearing the Root PME Status bits in
all PCI Express root ports during early resume. For this purpose,
add an early resume routine to the PCIe port driver and make this
driver be always registered, even if pci_ports_disable is set (in
which case the driver's only function is to provide the early
resume callback).
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Then we can use it instead of magic number 1.
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Then it can be used by others.
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Reviewed-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
These are already defined in pcilib's pci/header.h but not in kernel's
linux/pci_regs.h. Copy them to avoid using magic numbers.
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
This change corrects the fact that we were not reporting Gen2 link speeds
when we were in fact connected at Gen2 rates.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The Moorestown platform only has a few devices that actually support
PCI config cycles. The rest of the devices use an in-RAM MCFG space
for the purposes of device enumeration and initialization.
There are a few uglies in the fake support, like BAR sizes that aren't
a power of two, sizing detection, and writes to the real devices, but
other than that it's pretty straightforward.
Another way to think of this is not really as PCI at all, but just a
table in RAM describing which devices are present, their capabilities
and their offsets in MMIO space. This could have been done with a
special new firmware table on this platform, but given that we do have
some real PCI devices too, simply describing things in an MCFG type
space was pretty simple.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
LKML-Reference: <43F901BD926A4E43B106BF17856F07559FB80D08@orsmsx508.amr.corp.intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Change to populate the subsystem vendor and subsytem device IDs for
PCI-PCI bridges that implement the PCI Subsystem Vendor ID capability.
Previously bridges left subsystem vendor IDs unpopulated.
Signed-off-by: Gabe Black <gabe.black@ni.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Note: dom0 checking in v4 has been separated out into 2/2.
This patch enables P2P upstream forwarding in ACS capable PCIe switches.
It solves two potential problems in virtualization environment where a PCIe
device is assigned to a guest domain using a HW iommu such as VT-d:
1) Unintentional failure caused by guest physical address programmed
into the device's DMA that happens to match the memory address range
of other downstream ports in the same PCIe switch. This causes the PCI
transaction to go to the matching downstream port instead of go to the
root complex to get translated by VT-d as it should be.
2) Malicious guest software intentionally attacks another downstream
PCIe device by programming the DMA address into the assigned device
that matches memory address range of the downstream PCIe port.
We are in process of implementing device filtering software in KVM/XEN
management software to allow device assignment of PCIe devices behind a PCIe
switch only if it has ACS capability and with the P2P upstream forwarding bits
enabled. This patch is intended to work for both KVM and Xen environments.
Signed-off-by: Allen Kay <allen.m.kay@intel.com>
Reviewed-by: Mathew Wilcox <willy@linux.intel.com>
Reviewed-by: Chris Wright <chris@sous-sol.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
This adds a generic uio driver that can bind to any PCI device. First
user will be virtualization where a qemu userspace process needs to give
guest OS access to the device.
Interrupts are handled using the Interrupt Disable bit in the PCI
command register and Interrupt Status bit in the PCI status register.
All devices compliant to PCI 2.3 (circa 2002) and all compliant PCI
Express devices should support these bits. Driver detects this support,
and won't bind to devices which do not support the Interrupt Disable Bit
in the command register.
It's expected that more features of interest to virtualization will be
added to this driver in the future. Possibilities are: mmap for device
resources, MSI/MSI-X, eventfd (to interface with kvm), iommu.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Chris Wright <chrisw@redhat.com>
Signed-off-by: Hans J. Koch <hjk@linutronix.de>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* git://git.infradead.org/~dwmw2/iommu-2.6.31:
intel-iommu: Fix one last ia64 build problem in Pass Through Support
VT-d: support the device IOTLB
VT-d: cleanup iommu_flush_iotlb_psi and flush_unmaps
VT-d: add device IOTLB invalidation support
VT-d: parse ATSR in DMA Remapping Reporting Structure
PCI: handle Virtual Function ATS enabling
PCI: support the ATS capability
intel-iommu: dmar_set_interrupt return error value
intel-iommu: Tidy up iommu->gcmd handling
intel-iommu: Fix tiny theoretical race in write-buffer flush.
intel-iommu: Clean up handling of "caching mode" vs. IOTLB flushing.
intel-iommu: Clean up handling of "caching mode" vs. context flushing.
VT-d: fix invalid domain id for KVM context flush
Fix !CONFIG_DMAR build failure introduced by Intel IOMMU Pass Through Support
Intel IOMMU Pass Through Support
Fix up trivial conflicts in drivers/pci/{intel-iommu.c,intr_remapping.c}
Impact: cleanup, spec compliance
This patch does:
- Remove unused msi/msix_enable/disable macros.
User should use msi/msix_set_enable() functions instead.
- Remove unused msix_mask/unmask/pending macros.
These macros are useless because they are not based on any of
the PCI Local Bus Specifications properly.
It seems that they were written based on a draft of PCI spec,
and that the draft was the MSI-X ECN that underwent membership
review in September 2002.
(* In the draft, the size of a entry in MSI-X table was 64bit,
containing 32bit message data and DWORD aligned lower address
plus a pending bit and a mask bit.(30+1+1bit) The higher
address was placed in MSI-X capability structure and shared
by all entries.)
- Remove PCI_MSIX_FLAGS_BITMASK.
This definition also come from the draft ECN.
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Reviewed-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
The PCIe ATS capability makes the Endpoint be able to request the
DMA address translation from the IOMMU and cache the translation
in the device side, thus alleviate IOMMU pressure and improve the
hardware performance in the I/O virtualization environment.
Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
PCIe 1.1 base neither requires the endpoint to implement the entire
PCIe capability structure nor specifies default values of registers
that are not implemented by the device. So we only save and restore
registers that must be implemented by different device types if the
device PCIe capability version is 1.
PCIe 1.1 Capability Structure Expansion ECN and PCIe 2.0 requires
all registers in the PCIe capability to be either implemented or
hardwired to 0. Their PCIe capability version is 2.
Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
PCIe 2.0 defines several new registers (Device Control 2, Link Control 2,
and Slot Control 2). Save and retore them in pci_save_pcie_state() and
pci_restore_pcie_state().
Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
If a device has the SR-IOV capability, initialize it (set the ARI
Capable Hierarchy in the lowest numbered PF if necessary; calculate
the System Page Size for the VF MMIO, probe the VF Offset, Stride
and BARs). A lock for the VF bus allocation is also initialized if
a PF is the lowest numbered PF.
Reviewed-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Clean up register definitions related to PCI Express Hot plug.
- Add register definitions into include/linux/pci_regs.h, and use
them instead of pciehp's locally definied register definitions.
- Remove pciehp's locally defined register definitions
- Remove unused register definitions in pciehp.
- Some minor cleanups.
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
PCI Advanced Features Capability is introduced by "Conventional PCI
Advanced Caps ECN" (can be downloaded in pcisig.com). Add defines for
the various AF capabilities, including function level reset (FLR).
Reviewed-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Sometimes, it's necessary to enable software's ability to quiesce and
reset endpoint hardware with function-level granularity, so provide
support for it.
The patch implement Function Level Reset(FLR) feature following PCI-e
spec. And this is the first step. We would add more generic method, like
D0/D3, to allow more devices support this function.
The patch contains two functions. pcie_reset_function() is the new
driver API, and, contains some action to quiesce a device. The other
function is a helper: pcie_execute_reset_function() just executes the
reset for a particular device function.
Current the usage model is in KVM. Function reset is necessary for
assigning device to a guest, or moving it between partitions.
For Function Level Reset(FLR), please refer to PCI Express spec chapter
6.6.2.
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
This patch adds support for PCI Express Alternative Routing-ID
Interpretation (ARI) capability.
The ARI capability extends the Function Number field of the PCI Express
Endpoint by reusing the Device Number which is otherwise hardwired to 0.
With ARI, an Endpoint can have up to 256 functions.
Signed-off-by: Yu Zhao <yu.zhao@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Disable ASPM on pre-1.1 PCIe devices, as many of them don't implement it
correctly.
Tested-by: Jack Howarth <howarth@bromo.msbb.uc.edu>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
If the offset of PCI device's PM capability in its configuration space,
the mask of states that the device supports PME# from and the D1 and D2
support bits are cached in the corresponding struct pci_dev, the PCI
device PM code can be simplified quite a bit.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
PCI Express ASPM defines a protocol for PCI Express components in the D0
state to reduce Link power by placing their Links into a low power state
and instructing the other end of the Link to do likewise. This
capability allows hardware-autonomous, dynamic Link power reduction
beyond what is achievable by software-only controlled power management.
However, The device should be configured by software appropriately.
Enabling ASPM will save power, but will introduce device latency.
This patch adds ASPM support in Linux. It introduces a global policy for
ASPM, a sysfs file /sys/module/pcie_aspm/parameters/policy can control
it. The interface can be used as a boot option too. Currently we have
below setting:
-default, BIOS default setting
-powersave, highest power saving mode, enable all available ASPM
state and clock power management
-performance, highest performance, disable ASPM and clock power
management
By default, the 'default' policy is used currently.
In my test, power difference between powersave mode and performance mode
is about 1.3w in a system with 3 PCIE links.
Note: some devices might not work well with aspm, either because chipset
issue or device issue. The patch provide API (pci_disable_link_state),
driver can disable ASPM for specific device.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This reverts commit 6c723d5bd8.
It caused build errors on non-x86 platforms, config file confusion, and
even some boot errors on some x86-64 boxes. All around, not quite ready
for prime-time :(
Cc: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
PCI Express ASPM defines a protocol for PCI Express components in the D0
state to reduce Link power by placing their Links into a low power state
and instructing the other end of the Link to do likewise. This
capability allows hardware-autonomous, dynamic Link power reduction
beyond what is achievable by software-only controlled power management.
However, The device should be configured by software appropriately.
Enabling ASPM will save power, but will introduce device latency.
This patch adds ASPM support in Linux. It introduces a global policy for
ASPM, a sysfs file /sys/module/pcie_aspm/parameters/policy can control
it. The interface can be used as a boot option too. Currently we have
below setting:
-default, BIOS default setting
-powersave, highest power saving mode, enable all available ASPM
state
and clock power management
-performance, highest performance, disable ASPM and clock power
management
By default, the 'default' policy is used currently.
In my test, power difference between powersave mode and performance mode
is about 1.3w in a system with 3 PCIE links.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Bjorn Helgaas