lkml.org 
[lkml]   [2019]   [Oct]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v4 2/3] PCI: pciehp: Wait for PDS if in-band presence is disabled
    Date
    From: Alexandru Gagniuc <mr.nuke.me@gmail.com>

    When inband presence is disabled, PDS may come up at any time, or not
    at all. PDS being low may indicate that the card is still mating, and
    we could expect contact bounce to bring down the link as well.

    It is reasonable to assume that most cards will mate in a hotplug slot
    in about a second. Thus, when we know PDS only reflects out-of-band
    presence, it's worthwhile to wait the extra second or so to make sure
    the card is properly mated before loading the driver, and to prevent
    the hotplug code from disabling a device if the presence detect change
    goes active after the device is enabled.

    Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
    Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
    ---
    v2:
    replace while(true) loop with do...while
    v3
    remove unused variable declaration (pds)
    modify text of warning message
    v4
    remove "!!" boolean conversion from "if" condition for readability

    drivers/pci/hotplug/pciehp_hpc.c | 19 +++++++++++++++++++
    1 file changed, 19 insertions(+)

    diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
    index dc109d521f30..02d95ab27a12 100644
    --- a/drivers/pci/hotplug/pciehp_hpc.c
    +++ b/drivers/pci/hotplug/pciehp_hpc.c
    @@ -242,6 +242,22 @@ static bool pci_bus_check_dev(struct pci_bus *bus, int devfn)
    return found;
    }

    +static void pcie_wait_for_presence(struct pci_dev *pdev)
    +{
    + int timeout = 1250;
    + u16 slot_status;
    +
    + do {
    + pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
    + if (slot_status & PCI_EXP_SLTSTA_PDS)
    + return;
    + msleep(10);
    + timeout -= 10;
    + } while (timeout > 0);
    +
    + pci_info(pdev, "Timeout waiting for Presence Detect state to be set\n");
    +}
    +
    int pciehp_check_link_status(struct controller *ctrl)
    {
    struct pci_dev *pdev = ctrl_dev(ctrl);
    @@ -251,6 +267,9 @@ int pciehp_check_link_status(struct controller *ctrl)
    if (!pcie_wait_for_link(pdev, true))
    return -1;

    + if (ctrl->inband_presence_disabled)
    + pcie_wait_for_presence(pdev);
    +
    found = pci_bus_check_dev(ctrl->pcie->port->subordinate,
    PCI_DEVFN(0, 0));

    --
    2.18.1
    \
     
     \ /
      Last update: 2019-10-25 21:01    [W:4.159 / U:0.312 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site