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Lukas Wunner 493fb50e95 PCI: pciehp: Assume NoCompl+ for Thunderbolt ports
Certain Thunderbolt 1 controllers claim to support Command Completed events
(value of 0b in the No Command Completed Support field of the Slot
Capabilities register) but in reality they neither set the Command
Completed bit in the Slot Status register nor signal a Command Completed
interrupt:

  8086:1513  CV82524  [Light Ridge 4C  2010]
  8086:151a  DSL2310  [Eagle Ridge 2C  2011]
  8086:151b  CVL2510  [Light Peak 2C   2010]
  8086:1547  DSL3510  [Cactus Ridge 4C 2012]
  8086:1548  DSL3310  [Cactus Ridge 2C 2012]
  8086:1549  DSL2210  [Port Ridge 1C   2011]

All known newer chips (Redwood Ridge and onwards) set No Command Completed
Support, indicating that they do not support Command Completed events.

The user-visible impact is that after unplugging such a device, 2 seconds
elapse until pciehp is unbound.  That's because on ->remove,
pcie_write_cmd() is called via pcie_disable_notification() and every call
to pcie_write_cmd() takes 2 seconds (1 second for each invocation of
pcie_wait_cmd()):

  [  337.942727] pciehp 0000:0a:00.0:pcie204: Timeout on hotplug command 0x1038 (issued 21176 msec ago)
  [  340.014735] pciehp 0000:0a:00.0:pcie204: Timeout on hotplug command 0x0000 (issued 2072 msec ago)

That by itself has always been unpleasant, but the situation has become
worse with commit cc27b735ad ("PCI/portdrv: Turn off PCIe services during
shutdown"):  Now pciehp is unbound on ->shutdown.  Because Thunderbolt
controllers typically have 4 hotplug ports, every reboot and shutdown is
now delayed by 8 seconds, plus another 2 seconds for every attached
Thunderbolt 1 device.

Thunderbolt hotplug slots are not physical slots that one inserts cards
into, but rather logical hotplug slots implemented in silicon.  Devices
appear beyond those logical slots once a PCI tunnel is established on top
of the Thunderbolt Converged I/O switch.  One would expect commands written
to the Slot Control register to be executed immediately by the silicon, so
for simplicity we always assume NoCompl+ for Thunderbolt ports.

Fixes: cc27b735ad ("PCI/portdrv: Turn off PCIe services during shutdown")
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: stable@vger.kernel.org	# v4.12+
Cc: Sinan Kaya <okaya@codeaurora.org>
Cc: Yehezkel Bernat <yehezkel.bernat@intel.com>
Cc: Michael Jamet <michael.jamet@intel.com>
Cc: Andreas Noever <andreas.noever@gmail.com>
2018-01-23 14:28:41 -06:00
arch Revert "mm: replace p??_write with pte_access_permitted in fault + gup paths" 2017-12-15 18:53:22 -08:00
block Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-12-01 08:05:45 -05:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-12-11 16:32:45 -08:00
Documentation Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs 2017-12-15 12:46:48 -08:00
drivers PCI: pciehp: Assume NoCompl+ for Thunderbolt ports 2018-01-23 14:28:41 -06:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Revert "exec: avoid RLIMIT_STACK races with prlimit()" 2017-12-17 14:26:25 -08:00
include Merge branch 'WIP.x86-pti.base.prep-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-12-17 13:54:31 -08:00
init main: kernel_start: move housekeeping_init() before workqueue_init_early() 2017-11-27 08:56:57 -08:00
ipc Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
kernel Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-12-17 13:48:50 -08:00
lib Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-12-15 11:44:59 -08:00
mm Revert "mm: replace p??_write with pte_access_permitted in fault + gup paths" 2017-12-15 18:53:22 -08:00
net NFS client fixes for Linux 4.15-rc4 2017-12-16 13:12:53 -08:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2017-12-03 13:08:30 -05:00
scripts Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-12-15 11:44:59 -08:00
security KEYS: reject NULL restriction string when type is specified 2017-12-08 15:13:29 +00:00
sound sound fixes for 4.15-rc3 2017-12-06 10:49:14 -08:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-12-15 13:08:37 -08:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: x86: fix APIC page invalidation 2017-12-06 16:10:34 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild misc updates for v4.15 2017-11-17 17:51:33 -08:00
.mailmap Add Jason Gunthorpe as co-maintainer of the RDMA stack 2017-11-17 09:36:18 -08:00
COPYING
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-12-15 13:08:37 -08:00
Makefile Linux 4.15-rc4 2017-12-17 18:59:59 -08:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.