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From: Stuart Hayes <stuart.w.hayes@gmail.com>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: Austin Bolen <austin_bolen@dell.com>,
	keith.busch@intel.com, Alexandru Gagniuc <mr.nuke.me@gmail.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	"Gustavo A . R . Silva" <gustavo@embeddedor.com>,
	Sinan Kaya <okaya@kernel.org>,
	Oza Pawandeep <poza@codeaurora.org>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
	lukas@wunner.de, Stuart Hayes <stuart.w.hayes@gmail.com>
Subject: [PATCH v2 0/3] PCI: pciehp: Do not turn off slot if presence comes up after link
Date: Fri, 11 Oct 2019 16:51:24 -0400
Message-ID: <20191011205127.4884-1-stuart.w.hayes@gmail.com> (raw)

In older PCIe specs, PDS (presence detect) would come up when the
"in-band" presence detect pin connected, and would be up before DLLLA
(link active).

In PCIe 4.0 (as an ECN) and in PCIe 5.0, there is a new bit to show if
in-band presence detection can be disabled for the slot, and another bit
that disables it--and a recommendation that it should be disabled if it
can be. In addition, certain OEMs disable in-band presence detection
without implementing these bits.

This means it is possible to get a "card present" interrupt after the
link is up and the driver is loaded.  This causes an erroneous removal
of the device driver, followed by an immediate re-probing.

This patch set defines these new bits, uses them to disable in-band
presence detection if it can be, waits for PDS to go up if in-band
presence detection is disabled, and adds a DMI table that will let us
know if we should assume in-band presence is disabled on a system.

The first two patches in this set come from a patch set that was
submitted but not accepted many months ago by Alexandru Gagniuc [1].
The first is unmodified, the second has the commit message and timeout 
modified.

[1] https://patchwork.kernel.org/cover/10909167/
    [v3,0/4] PCI: pciehp: Do not turn off slot if presence comes up after link

v2:
- modify loop in pcie_wait_for_presence to do..while

Alexandru Gagniuc (2):
  PCI: pciehp: Add support for disabling in-band presence
  PCI: pciehp: Wait for PDS if in-band presence is disabled

Stuart Hayes (1):
  PCI: pciehp: Add dmi table for in-band presence disabled

 drivers/pci/hotplug/pciehp.h     |  1 +
 drivers/pci/hotplug/pciehp_hpc.c | 45 +++++++++++++++++++++++++++++++-
 include/uapi/linux/pci_regs.h    |  2 ++
 3 files changed, 47 insertions(+), 1 deletion(-)

-- 
2.18.1


             reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-11 20:51 Stuart Hayes [this message]
2019-10-11 20:51 ` [PATCH v2 1/3] PCI: pciehp: Add support for disabling in-band presence Stuart Hayes
2019-10-11 20:51 ` [PATCH v2 2/3] PCI: pciehp: Wait for PDS if in-band presence is disabled Stuart Hayes
2019-10-12  7:34   ` Andy Shevchenko
2019-10-11 20:51 ` [PATCH v2 3/3] PCI: pciehp: Add dmi table for in-band presence disabled Stuart Hayes

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