When removing PCI devices below a hotplug bridge, pciehp marks them as
disconnected if the card is no longer present in the slot or it quiesces
them if the card is still present (by disabling INTx interrupts, bus
mastering and SERR# reporting).

To detect whether the card is still present, pciehp checks the Presence
Detect State bit in the Slot Status register.  The problem with this
approach is that even if the card is present, the link to it may be
down, and it that case it would be better to mark the devices as
disconnected instead of trying to quiesce them.  Moreover, if the card
in the slot was quickly replaced by another one, the Presence Detect
State bit would be set, yet trying to quiesce the new card's devices
would be wrong and the correct thing to do is to mark the previous
card's devices as disconnected.

Instead of looking at the Presence Detect State bit, it is better to
differentiate whether the card was surprise removed versus safely
removed (via sysfs or an Attention Button press).  On surprise removal,
the devices should be marked as disconnected, whereas on safe removal it
is correct to quiesce the devices.

The knowledge whether a surprise removal or a safe removal is at hand
does exist further up in the call stack:  A surprise removal is
initiated by pciehp_handle_presence_or_link_change(), a safe removal by
pciehp_handle_disable_request().

Pass that information down to pciehp_unconfigure_device() and use it in
lieu of the Presence Detect State bit.  While there, add kernel-doc to
pciehp_unconfigure_device() and pciehp_configure_device().
Tested-by: NAlexandru Gagniuc <mr.nuke.me@gmail.com>
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Cc: Keith Busch <keith.busch@intel.com>

Per Mika's request, add an explicit break to the last case of switch
statements everywhere in pciehp to be more defensive towards future
amendments.

Per Gustavo's request, mark all non-empty implicit fallthroughs with a
comment to silence warnings triggered by -Wimplicit-fallthrough=2.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: NGustavo A. R. Silva <gustavo@embeddedor.com>

pciehp's IRQ thread ensures accessibility of the port by runtime resuming
its parent to D0.  However when the slot is enabled/disabled, the port
itself needs to be in D0 because its secondary bus is accessed in:

    pciehp_check_link_status(),
    pciehp_configure_device() (both called from board_added())
and
    pciehp_unconfigure_device() (called from remove_board()).

Thus, acquire a runtime PM ref on enable/disablement of the slot.

Yinghai Lu additionally discovered that some SkyLake servers feature a
Power Controller for their PCIe hotplug ports (PCIe r3.1, sec 6.7.1.8)
which requires the port to be in D0 when invoking

    pciehp_power_on_slot() (likewise called from board_added()).

If slot power is turned on while in D3hot, link training later fails:
https://lkml.kernel.org/r/20170205073454.GA253@wunner.de

The spec is silent about such a requirement, but it seems prudent to
assume that any hotplug port with a Power Controller may need this.

The present commit holds a runtime PM ref whenever slot power is turned
on and off, but it doesn't keep the port in D0 as long as slot power is
on.  If vendors determine that's necessary, they need to amend pciehp to
acquire a runtime PM ref in pciehp_power_on_slot() and release one in
pciehp_power_off_slot().
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>

A hotplug port's Slot Status register does not count how often each type
of event occurred, it only records the fact *that* an event has occurred.

Previously pciehp queued a work item for each event.  But if it missed
an event, e.g. removal of a card in-between two back-to-back insertions,
it queued up the wrong work item or no work item at all.  Commit
fad214b0 ("PCI: pciehp: Process all hotplug events before looking
for new ones") sought to improve the situation by shrinking the window
during which events may be missed.

But Stefan Roese reports unbalanced Card present and Link Up events,
suggesting that we're still missing events if they occur very rapidly.
Bjorn Helgaas responds that he considers pciehp's event handling
"baroque" and calls for its simplification and rationalization:
https://lkml.kernel.org/r/20180202192045.GA53759@bhelgaas-glaptop.roam.corp.google.com

It gets worse once a hotplug port is runtime suspended:  The port can
signal an interrupt while it and its parents are in D3hot, i.e. while
it is inaccessible.  By the time we've runtime resumed all parents to D0
and read the port's Slot Status register, we may have missed an arbitrary
number of events.  Event handling therefore needs to be reworked to
become resilient to missed events.

Assume that a Presence Detect Changed event has occurred.
Consider the following truth table:
- Slot is in OFF_STATE and is currently empty.    => Do nothing.
  (The event is trailing a Link Down or we've
  missed an insertion and subsequent removal.)
- Slot is in OFF_STATE and is currently occupied. => Turn the slot on.
- Slot is in ON_STATE  and is currently empty.    => Turn the slot off.
- Slot is in ON_STATE  and is currently occupied. => Turn the slot off,
  (Be cautious and assume the card in                then back on.
  the slot isn't the same as before.)

This leads to the following simple algorithm:
1 If the slot is in ON_STATE, turn it off unconditionally.
2 If the slot is currently occupied, turn it on.

Because those actions are now carried out synchronously, rather than by
scheduled work items, pciehp reacts to the *current* situation and
missed events no longer matter.

Data Link Layer State Changed events can be handled identically to
Presence Detect Changed events.  Note that in the above truth table,
a Link Up trailing a Card present event didn't have to be accounted for:
It is filtered out by pciehp_check_link_status().

As for Attention Button Pressed events, PCIe r4.0, sec 6.7.1.5 says:
"Once the Power Indicator begins blinking, a 5-second abort interval
exists during which a second depression of the Attention Button cancels
the operation."  In other words, the user can only expect the system to
react to a button press after it starts blinking.  Missed button presses
that occur in-between are irrelevant.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Cc: Stefan Roese <sr@denx.de>
Cc: Mayurkumar Patel <mayurkumar.patel@intel.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>

No callers of pciehp_enable/disable_slot() outside of pciehp_ctrl.c
remain, so declare the functions static.  For now this requires forward
declarations.  Those can be eliminated by reshuffling functions once the
ongoing effort to refactor the driver has settled.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Previously slot enablement and disablement could happen concurrently.
But now it's under the exclusive control of the IRQ thread, rendering
the locking obsolete.  Drop it.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Besides the IRQ thread, there are several other places in the driver
which enable or disable the slot:

- pciehp_probe() enables the slot if it's occupied and the pciehp_force
  module parameter is used.

- pciehp_resume() enables or disables the slot after system sleep.

- pciehp_queue_pushbutton_work() enables or disables the slot after the
  5 second delay following an Attention Button press.

- pciehp_sysfs_enable_slot() and pciehp_sysfs_disable_slot() enable or
  disable the slot on sysfs write.

This requires locking and complicates pciehp's state machine.

A simplification can be achieved by enabling and disabling the slot
exclusively from the IRQ thread.

Amend the functions listed above to request slot enable/disablement from
the IRQ thread by either synthesizing a Presence Detect Changed event or,
in the case of a disable user request (via sysfs or an Attention Button
press), submitting a newly introduced force disable request.  The latter
is needed because the slot shall be forced off despite being occupied.
For this force disable request, avoid colliding with Slot Status register
bits by using a bit number greater than 16.

For synchronous execution of requests (on sysfs write), wait for the
request to finish and retrieve the result.  There can only ever be one
sysfs write in flight due to the locking in kernfs_fop_write(), hence
there is no risk of returning the result of a different sysfs request to
user space.

The POWERON_STATE and POWEROFF_STATE is now no longer entered by the
above-listed functions, but solely by the IRQ thread when it begins a
power transition.  Afterwards, it moves to STATIC_STATE.  The same
applies to canceling the Attention Button work, it likewise becomes an
IRQ thread only operation.

An immediate consequence is that the POWERON_STATE and POWEROFF_STATE is
never observed by the IRQ thread itself, only by functions called in a
different context, such as pciehp_sysfs_enable_slot().  So remove
handling of these states from pciehp_handle_button_press() and
pciehp_handle_link_change() which are exclusively called from the IRQ
thread.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

handle_button_press_event() currently determines whether the slot has
been turned on or off by looking at the Power Controller Control bit in
the Slot Control register.  This assumes that an attention button
implies presence of a power controller even though that's not mandated
by the spec.  Moreover the Power Controller Control bit is unreliable
when a power fault occurs (PCIe r4.0, sec 6.7.1.8).  This issue has
existed since the driver was introduced in 2004.

Fix by replacing STATIC_STATE with ON_STATE and OFF_STATE and tracking
whether the slot has been turned on or off.  This is also a required
ingredient to make pciehp resilient to missed events, which is the
object of an upcoming commit.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Previously the slot workqueue was used to handle events and enable or
disable the slot.  That's no longer the case as those tasks are done
synchronously in the IRQ thread.  The slot workqueue is thus merely used
to handle a button press after the 5 second delay and only one such work
item may be in flight at any given time.  A separate workqueue isn't
necessary for this simple task, so use the system workqueue instead.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Up until now, pciehp's IRQ handler schedules a work item for each event,
which in turn schedules a work item to enable or disable the slot.  This
double indirection was necessary because sleeping wasn't allowed in the
IRQ handler.

However it is now that pciehp has been converted to threaded IRQ handling
and polling, so handle events synchronously in pciehp_ist() and remove
the work item infrastructure (with the exception of work items to handle
a button press after the 5 second delay).

For link or presence change events, move the register read to determine
the current link or presence state behind acquisition of the slot lock
to prevent it from becoming stale while the lock is contended.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

If the attention button is pressed to power on the slot AND the user
powers on the slot via sysfs before 5 seconds have elapsed AND powering
on the slot fails because either the slot is unoccupied OR the latch is
open, we neglect turning off the green LED so it keeps on blinking.

That's because the error path of pciehp_sysfs_enable_slot() doesn't call
pciehp_green_led_off(), unlike pciehp_power_thread() which does.
The bug has been present since 2004 when the driver was introduced.

Fix by deduplicating common code in pciehp_sysfs_enable_slot() and
pciehp_power_thread() into a wrapper function pciehp_enable_slot() and
renaming the existing function to __pciehp_enable_slot().  Same for
pciehp_disable_slot().  This will also simplify the upcoming rework of
pciehp's event handling.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Since commit 0f4bd801 ("PCI: hotplug: Drop checking of PCI_BRIDGE_
CONTROL in *_unconfigure_device()"), pciehp_unconfigure_device() can no
longer fail, so declare it and its sole caller remove_board() void, in
keeping with the usual kernel pattern that enablement can fail, but
disablement cannot.  No functional change intended.
Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>

pciehp_disable_slot() checks if the ctrl attribute of the slot is NULL
and bails out if so.  However the function is not called prior to the
attribute being set in pcie_init_slot(), and pcie_init_slot() is not
called if ctrl is NULL.  So the check is unnecessary.  Drop it.

It has been present ever since the driver was introduced in 2004, but it
was already unnecessary back then:
https://git.kernel.org/tglx/history/c/c16b4b14d980Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

In preparation to enabling -Wimplicit-fallthrough, mark switch cases where
we are expecting to fall through.

Warning level 2 was used: -Wimplicit-fallthrough=2
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Add SPDX GPL-2.0+ to all PCI files that specified the GPL and allowed
either GPL version 2 or any later version.

Remove the boilerplate GPL version 2 or later language, relying on the
assertion in b2441318 ("License cleanup: add SPDX GPL-2.0 license
identifier to files with no license") that the SPDX identifier may be used
instead of the full boilerplate text.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

A surprise link down may retrain very quickly causing the same slot
generate a link up event before handling the link down event completes.

Since the link is active, the power off work queued from the first link
down will cause a second down event when power is disabled. However, the
link up event sets the slot state to POWERON_STATE before the event to
handle this is enqueued, making the second down event believe it needs to
do something.

This creates constant link up and down event cycle.

To prevent this it is better to handle each event at the time in order it
occurred, so change the driver to use ordered workqueue instead.

A normal device hotplug triggers two events (presense detect and link up)
that are already handled properly in the driver but we currently log an
error if we find an existing device in the slot. Since this is not an error
change the log level to be debug instead to avoid scaring users.

This is based on the original work by Ashok Raj.

Link: https://patchwork.kernel.org/patch/9469023Suggested-by: NBjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

This reverts commit 68db9bc8.

Yinghai reported that the following manual hotplug sequence:

  # echo 0 > /sys/bus/pci/slots/8/power
  # echo 1 > /sys/bus/pci/slots/8/power

worked in v4.9, but fails in v4.10-rc1, and that reverting 68db9bc8
("PCI: pciehp: Add runtime PM support for PCIe hotplug ports") makes it
work again.

Fixes: 68db9bc8 ("PCI: pciehp: Add runtime PM support for PCIe hotplug ports")
Link: https://lkml.kernel.org/r/CAE9FiQVCMCa7iVyuwp9z6VrY0cE7V_xghuXip28Ft52=8QmTWw@mail.gmail.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=193951Reported-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

If an error occurs when enabling a slot, pciehp_power_thread() turns off
the power indicator.  But if the only error is that the slot was already
enabled, we should leave the power indicator on.

Return success if called to enable an already-enabled slot.
This is in the same spirit of the special handling for EEXISTS when
pciehp_configure_device() determines the slot devices already exist.
Signed-off-by: NAshok Raj <ashok.raj@intel.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NKeith Busch <keith.busch@intel.com>

Linux 4.8 added support for runtime suspending PCIe ports to D3hot with
commit 006d44e4 ("PCI: Add runtime PM support for PCIe ports"), but
excluded hotplug ports.  Those are now afforded runtime PM by the present
commit.

Hotplug ports require a few extra considerations:

- The configuration space of the port remains accessible in D3hot, so all
  the functions to read or modify the Slot Status and Slot Control
  registers need not be modified.  Even turning on slot power doesn't seem
  to require the port to be in D0, at least the PCIe spec doesn't say so
  and I confirmed that by testing with a Thunderbolt controller.

- However D0 is required to access devices on the secondary bus.  This
  happens in pciehp_check_link_status() and pciehp_configure_device() (both
  called from board_added()) and in pciehp_unconfigure_device() (called
  from remove_board()), so acquire a runtime PM ref for their invocation.

- The hotplug port stays active as long as it has active children.  If all
  hotplugged devices below the port runtime suspend, the port is allowed to
  runtime suspend as well.  Plug and unplug detection continues to work in
  D3hot.

- Hotplug interrupts are delivered in-band, so while the hotplug port
  itself is allowed to go to D3hot, its parent ports must stay in D0 for
  interrupts to come through.  Add a corresponding restriction to
  pci_dev_check_d3cold().

- Runtime PM may only be allowed if the hotplug port is handled natively by
  the OS.  On ACPI systems, the port may alternatively be handled by the
  firmware and things break if the OS puts the port into D3 behind the
  firmware's back:  E.g. Thunderbolt hotplug ports on non-Macs are handled
  by Intel's firmware in System Management Mode and the firmware is known
  to access devices on the port's secondary bus without checking first if
  the port is in D0: https://bugzilla.kernel.org/show_bug.cgi?id=53811Signed-off-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
CC: Mika Westerberg <mika.westerberg@linux.intel.com>

Long ago, we updated a "switch_save" field based on the latch status.  But
switch_save was unused, and ed6cbcf2 ("[PATCH] pciehp: miscellaneous
cleanups") removed it.

We no longer use the latch status, so remove calls to
pciehp_get_latch_status().  No functional change intended.
Tested-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NMika Westerberg <mika.westerberg@linux.intel.com>

Print slot name consistently as "Slot(%s)".  I don't know whether that's
ideal, but we can at least do it the same way all the time.  No functional
change intended.
Tested-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NMika Westerberg <mika.westerberg@linux.intel.com>

Previously we read Slot Status when handling a surprise event.  But Slot
Status might have changed since we identified the event, and the event_type
already tells us whether to enable or disable the slot, so there's no need
to read it again.

Remove handle_surprise_event() and queue the power work directly.

[bhelgaas: changelog]
Tested-by: NLukas Wunner <lukas@wunner.de>
Signed-off-by: NMayurkumar Patel <mayurkumar.patel@intel.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: NRajat Jain <rajatxjain@gmail.com>

Clear the LED attention status after a successful device add.  It is
possible the attention LED was on from a previous power fault or link
failure, and a subsequent successful device insert insertion should clear
it.
Signed-off-by: NKeith Busch <keith.busch@intel.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

When called from pciehp_sysfs_disable_slot(), the call to
pciehp_disable_slot() was not protected by the hotplug mutex.

Hold slot->hotplug_lock while calling pciehp_disable_slot().
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NRajat Jain <rajatxjain@gmail.com>

Up to now, work items to be queued to be handled by pciehp_power_thread()
are allocated using kmalloc() in three different locations.  If not needed,
kfree() is called to free the allocated data.

Introduce a separate function to allocate the work item and queue it, and
call it only if needed.  This reduces code duplication and avoids having to
free memory if the work item does not need to get executed.

[bhelgaas: tweak "no memory" message, make pciehp_queue_power_work() static]
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

The pciehp_handle_*() functions (pciehp_handle_attention_button(), etc.)
only contain a line or two of useful code, so it's clumsy to put
them in separate functions.  All they so is add an event to a work queue,
and it's clearer to see that directly in the ISR.

Inline them directly into pcie_isr().  No functional change.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NRajat Jain <rajatja@google.com>
Acked-by: NYinghai Lu <yinghai@kernel.org>

Rename queue_interrupt_event() to pciehp_queue_interrupt_event() so we can
make it extern and call it from pcie_isr().

No functional change.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NRajat Jain <rajatja@google.com>
Acked-by: NYinghai Lu <yinghai@kernel.org>

Nobody looks at the return value from queue_interrupt_event(), so errors
were silently ignored.  Convert it to a "void" function and note the error
in the dmesg log.

No functional change except the new message.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NRajat Jain <rajatja@google.com>
Acked-by: NYinghai Lu <yinghai@kernel.org>

The pciehp debug logging is overly verbose and often redundant.  Almost all
of the information printed by dbg_ctrl() is also printed by the normal PCI
core enumeration code and by pcie_init().

Remove the redundant debug info.

When claiming a pciehp bridge, we print the slot characteristics, e.g.,

  Slot #6 AttnBtn- AttnInd- PwrInd- PwrCtrl- MRL- Interlock- NoCompl+ LLActRep+

Add the Hot-Plug Capable and Hot-Plug Surprise bits to this information,
and print it all in the same order as lspci does.

No functional change except the message text changes.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NRajat Jain <rajatja@google.com>
Acked-by: NYinghai Lu <yinghai@kernel.org>

The PCIe spec (r3.0, sec 7.8.9) says Hot-Plug Surprise indicates support
for surprise *removal*, but pciehp checked this to determine if it should
handle presence detect interrupts for device *addition*.

Allow surprise device addition even if the slot doesn't advertise support
for surprise removal.

Keith has a platform with slots for front-loading SFF devices.  The slots
do not have attention buttons and do not support surprise removal, but they
do have presence detect.  In that case, we still want to use presence
detect for device addition.

Keith's original patch handled surprise insertions only if Hot-Plug Capable
is set.  I think that test is superfluous because pciehp only claims slots
that advertise Hot-Plug Capable (see get_port_device_capability()).

Link: http://lkml.kernel.org/r/1419275223-14602-1-git-send-email-keith.busch@intel.comBased-on-patch-by: NKeith Busch <keith.busch@intel.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: NRajat Jain <rajatxjain@gmail.com>

Merge quoted strings that are broken across lines into a single entity.
The compiler merges them anyway, but checkpatch complains about it, and
merging them makes it easier to grep for strings.

No functional change.

[bhelgaas: changelog, do the same for everything under drivers/pci]
Signed-off-by: NRyan Desfosses <ryan@desfo.org>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Fix various whitespace errors.

No functional change.

[bhelgaas: fix other similar problems]
Signed-off-by: NRyan Desfosses <ryan@desfo.org>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Minor whitespace cleanup; no functional change.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

In case a card is physically yanked out, it should immediately be removed,
regardless of the "surprise" capability bit. Thus:

  - Always handle the physical removal - regardless of the "surprise" bit.
  - Don't use "surprise" capability when making decisions about enabling
    presence detect notifications.
  - Reword the comments to indicate the intent.
Signed-off-by: NRajat Jain <rajatxjain@gmail.com>
Signed-off-by: NRajat Jain <rajatjain@juniper.net>
Signed-off-by: NGuenter Roeck <groeck@juniper.net>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

If we found device already exists during hot add device, we should leave
it, not turn the slot off.
Signed-off-by: NYijing Wang <wangyijing@huawei.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Today it is there is no protection around pciehp_enable_slot() and
pciehp_disable_slot() to ensure that they complete before another
hot-plug operation can be done on that particular slot.

This patch introduces the slot->hotplug_lock to ensure that any hotplug
operations (add / remove) complete before another hotplug event can begin
processing on that particular slot.
Signed-off-by: NRajat Jain <rajatxjain@gmail.com>
Signed-off-by: NRajat Jain <rajatjain@juniper.net>
Signed-off-by: NGuenter Roeck <groeck@juniper.net>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Today, this is how all the hotplug and unplug events work:

Hotplug / Removal needs to be done
  => Set slot->state (protected by slot->lock) to either
    POWERON_STATE (for enabling) or POWEROFF_STATE (for disabling).
  => Submit the work item for pciehp_power_thread() to slot->wq.

Problem:
  There is a problem if the hotplug events can happen fast enough that
  they do not give SW enough time to add or remove the new devices.

  => Assume: Event for unplug comes (e.g. surprise removal). But
     before the pciehp_power_thread() work item was executed, the
     card was replaced by another card, causing surprise hotplug event.

  => What goes wrong:
    => The hot-removal event sets slot->state to POWEROFF_STATE, and
       schedules the pciehp_power_thread().
    => The hot-add event sets slot->state to POWERON_STATE, and
       schedules the pciehp_power_thread().
    => Now the pciehp_power_thread() is scheduled twice, and on both
       occasions it will find POWERON_STATE and will try to add the
       devices on the slot, and will fail complaining that the devices
       already exist.

  => Why this is a problem: If the device was replaced between the hot
     removal and hot-add, then we should unload the old driver and
     reload the new one. This does not happen today. The kernel or the
     driver is not even aware that the device was replaced.

     The problem is that the pciehp_power_thread() only looks at the
     slot->state which would only contain the *latest* state - not
     the actual event (add / remove) that was the intent of the IRQ
     handler who submitted the work.

What this patch does:

  => Hotplug events pass on an actual request (for addition or removal)
     to pciehp_power_thread() which is local to that work item
     submission.

  => pciehp_power_thread() does not need to look at slote->state and
     hence no locks needed in that.

  => Essentially this results in all the hotplug and unplug events
     "replayed" by pciehp_power_thread().
Signed-off-by: NRajat Jain <rajatxjain@gmail.com>
Signed-off-by: NRajat Jain <rajatjain@juniper.net>
Signed-off-by: NGuenter Roeck <groeck@juniper.net>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

It does not make much sense to refuse to disable a slot if an adapter is
not present or the latch is open. If an adapter is not present, it provides
an even better reason to disable the device slot.

This is specially a problem for link state hot-plug, because some ports use
in band mechanism for presence detection. Thus when link goes down,
presence detect also goes down. We _want_ that the removal should take
place in such case.

Thus remove the checks for adapter and latch in pciehp_disable_slot()
Signed-off-by: NRajat Jain <rajatxjain@gmail.com>
Signed-off-by: NRajat Jain <rajatjain@juniper.net>
Signed-off-by: NGuenter Roeck <groeck@juniper.net>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

A lot of systems do not have the fancy buttons and LEDs, and instead
want to rely only on the Link state change events to drive the hotplug
and removal state machinery.
(http://www.spinics.net/lists/hotplug/msg05802.html)

This patch adds support for that functionality. Here are the details
about the patch itself:

* Define and use interrupt events for linkup / linkdown.

* Make the pcie_isr() also look at link events, and direct control to
  corresponding (new) link state change handler function.

* Introduce the functions to handle link-up and link-down events and
  queue the add / removal work in the slot->wq to be processed by
  pciehp_power_thread()

As a side note, this patch also fixes the bug
https://bugzilla.kernel.org/show_bug.cgi?id=65521 "pciehp ignores Data Link
Layer State Changed bit."
Signed-off-by: NRajat Jain <rajatxjain@gmail.com>
Signed-off-by: NRajat Jain <rajatjain@juniper.net>
Signed-off-by: NGuenter Roeck <groeck@juniper.net>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Previously, the caller checked ATTN_LED() or PWR_LED() to see whether the
slot has indicators before setting the indicator state.  That clutters the
caller unnecessarily, so this moves the test inside the callees.  The test
may not even be necessary; per spec it should be harmless to try to turn on
a non-existent LED.  But checking first does avoid unnecessary hotplug
commands.

No functional change.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>