Need to use it in _e1000e_disable_aspm.  This routine is used for error
recovery, where the pci_bus_sem is already held, and we don't want
pci_disable_link_state to try to take it again.  So add a locked variant
for use in cases like this.

Found lock up:

[ 2374.654557] kworker/32:1    D ffff881027f6b0f0     0  6075      2 0x00000000
[ 2374.654816]  ffff88503f099a68 0000000000000046 ffff88503f098000 0000000000004000
[ 2374.654837]  00000000001d1ec0 ffff88503f099fd8 00000000001d1ec0 ffff88503f099fd8
[ 2374.654860]  0000000000004000 00000000001d1ec0 ffff88503dcc8000 ffff88503f090000
[ 2374.654880] Call Trace:
[ 2374.654898]  [<ffffffff810b1302>] ? __lock_acquired+0x3a/0x224
[ 2374.654914]  [<ffffffff81c2b59c>] ? _raw_spin_unlock_irq+0x30/0x36
[ 2374.654925]  [<ffffffff810b069d>] ? trace_hardirqs_on_caller+0x1f/0x178
[ 2374.654936]  [<ffffffff81c2ab24>] rwsem_down_failed_common+0xd3/0x103
[ 2374.654945]  [<ffffffff810b158f>] ? __lock_contended+0x3a/0x2a2
[ 2374.654955]  [<ffffffff81c2ab7b>] rwsem_down_read_failed+0x12/0x14
[ 2374.654967]  [<ffffffff813371e4>] call_rwsem_down_read_failed+0x14/0x30
[ 2374.654981]  [<ffffffff8135df20>] ? pci_disable_link_state+0x5f/0xf5
[ 2374.654990]  [<ffffffff81c2a0e6>] ? down_read+0x7e/0x91
[ 2374.654999]  [<ffffffff8135df20>] ? pci_disable_link_state+0x5f/0xf5
[ 2374.655008]  [<ffffffff8135df20>] pci_disable_link_state+0x5f/0xf5
[ 2374.655024]  [<ffffffff81661796>] e1000e_disable_aspm+0x55/0x5a
[ 2374.655037]  [<ffffffff816677eb>] e1000_io_slot_reset+0x59/0xea
[ 2374.655048]  [<ffffffff8135fe0d>] ? report_mmio_enabled+0x5d/0x5d
[ 2374.655057]  [<ffffffff8135fe3b>] report_slot_reset+0x2e/0x5d
[ 2374.655072]  [<ffffffff8135369e>] pci_walk_bus+0x8a/0xb7
[ 2374.655081]  [<ffffffff8135fe0d>] ? report_mmio_enabled+0x5d/0x5d
[ 2374.655091]  [<ffffffff813603be>] broadcast_error_message+0xa4/0xb2
[ 2374.655101]  [<ffffffff81352c71>] ? pci_bus_read_config_dword+0x72/0x80
[ 2374.655110]  [<ffffffff813606df>] do_recovery+0x9e/0xf9
[ 2374.655120]  [<ffffffff81360786>] handle_error_source+0x4c/0x51
[ 2374.655129]  [<ffffffff81360974>] aer_isr_one_error+0x1e9/0x21a
[ 2374.655138]  [<ffffffff81360a6c>] aer_isr+0xc7/0xcc
[ 2374.655147]  [<ffffffff813609a5>] ? aer_isr_one_error+0x21a/0x21a
[ 2374.655159]  [<ffffffff81096d9f>] process_one_work+0x237/0x3ec
[ 2374.655168]  [<ffffffff81096d10>] ? process_one_work+0x1a8/0x3ec
[ 2374.655178]  [<ffffffff8109728d>] worker_thread+0x17c/0x240
[ 2374.655186]  [<ffffffff810b0803>] ? trace_hardirqs_on+0xd/0xf
[ 2374.655196]  [<ffffffff81097111>] ? manage_workers+0xab/0xab
[ 2374.655209]  [<ffffffff8109c8ed>] kthread+0xa0/0xa8
[ 2374.655223]  [<ffffffff81c332d4>] kernel_thread_helper+0x4/0x10
[ 2374.655232]  [<ffffffff81c2b880>] ? retint_restore_args+0xe/0xe
[ 2374.655243]  [<ffffffff8109c84d>] ? __init_kthread_worker+0x5b/0x5b
[ 2374.655252]  [<ffffffff81c332d0>] ? gs_change+0xb/0xb

when aer happens,
pci_walk_bus already have down_read(&pci_bus_sem)...
then report_slot_reset
        ==> e1000_io_slot_reset
                ==> e1000e_disable_aspm
                        ==> pci_disable_link_state...

We can not use pci_disable_link_state, and it will try to hold pci_bus_sem again.

Try to have __pci_disable_link_state that will not need to hold pci_bus_sem.

-v2: change name to pci_disable_link_state_locked() according to Jesse.

[jbarnes: make sure new function is exported for modules]
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

v3 -> v2: Moved ASPM enabling logic to pci_set_power_state()
v2 -> v1: Preserved the logic in pci_raw_set_power_state()
	: Added ASPM enabling logic after scanning Root Bridge
	: http://marc.info/?l=linux-pci&m=130046996216391&w=2
v1	: http://marc.info/?l=linux-pci&m=130013164703283&w=2

The assumption made in commit 41cd766b
(PCI: Don't enable aspm before drivers have had a chance to veto it) that
pci_enable_device() will result in re-configuring ASPM when aspm_policy is
POWERSAVE is no longer valid.  This is due to commit
97c145f7 (PCI: read current power state
at enable time) which resets dev->current_state to D0. Due to this the
call to pcie_aspm_pm_state_change() is never made. Note the equality check
(below) that returns early:
./drivers/pci/pci.c: pci_raw_set_pci_power_state()
546         /* Check if we're already there */
547         if (dev->current_state == state)
548                 return 0;

Therefore OSPM never configures the PCIe links for ASPM to turn them "on".

Fix it by configuring ASPM from the pci_enable_device() code path. This
also allows a driver such as the e1000e networking driver a chance to
disable ASPM (L0s, L1), if need be, prior to enabling the device. A
driver may perform this action if the device is known to mis-behave
wrt ASPM.
Signed-off-by: NNaga Chumbalkar <nagananda.chumbalkar@hp.com>
Acked-by: NRafael J. Wysocki <rjw@sisk.pl>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

We currently refuse to touch the ASPM registers if the BIOS tells us that
ASPM isn't supported. This can cause problems if the BIOS has (for any
reason) enabled ASPM on some devices anyway. Change the code such that we
explicitly clear ASPM if the FADT indicates that ASPM isn't supported,
and make sure we tidy up appropriately on device removal in order to deal
with the hotplug case. If ASPM is disabled because the BIOS doesn't hand
over control then we won't touch the registers.
Signed-off-by: NMatthew Garrett <mjg@redhat.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

The ACPI FADT table includes an ASPM control bit. If the bit is set, do
not enable ASPM since it may indicate that the platform doesn't actually
support the feature.
Tested-by: NJack Howarth <howarth@bromo.msbb.uc.edu>
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NJesse 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: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>