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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 0/3] PCI: pciehp: Do not turn off slot if presence comes up after link
Date:   Tue,  1 Oct 2019 17:14:16 -0400
Message-Id: <20191001211419.11245-1-stuart.w.hayes@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.

This patch set is based on a patch set [1] submitted many months ago by
Alexandru Gagniuc, who is no longer working on it.

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

Stuart Hayes (3):
  PCI: pciehp: Add support for disabling in-band presence
  PCI: pciehp: Wait for PDS when in-band presence is disabled
  PCI: pciehp: Add dmi table for systems with 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