From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Stuart Hayes <stuart.w.hayes@gmail.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
Austin Bolen <austin_bolen@dell.com>,
Keith Busch <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>,
"Gustavo A . R . Silva" <gustavo@embeddedor.com>,
Sinan Kaya <okaya@kernel.org>,
Oza Pawandeep <poza@codeaurora.org>,
linux-pci@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Lukas Wunner <lukas@wunner.de>
Subject: Re: [PATCH v4 2/3] PCI: pciehp: Wait for PDS if in-band presence is disabled
Date: Fri, 25 Oct 2019 22:16:59 +0300 [thread overview]
Message-ID: <CAHp75Vd54iDEe0ucTW8Gz9Q6cDGnA88XcBMy9-C5P1QuLzDm0Q@mail.gmail.com> (raw)
In-Reply-To: <20191025190047.38130-3-stuart.w.hayes@gmail.com>
On Fri, Oct 25, 2019 at 10:01 PM Stuart Hayes <stuart.w.hayes@gmail.com> wrote:
>
> 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.
>
FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> 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
>
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2019-10-25 19:17 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-25 19:00 [PATCH v4 0/3] PCI: pciehp: Do not turn off slot if presence comes up after link Stuart Hayes
2019-10-25 19:00 ` [PATCH v4 1/3] PCI: pciehp: Add support for disabling in-band presence Stuart Hayes
2019-10-25 19:15 ` Andy Shevchenko
2019-11-27 1:36 ` Bjorn Helgaas
2019-11-27 2:19 ` Stuart Hayes
2019-12-31 22:06 ` Stuart Hayes
2020-01-29 13:15 ` Libor Pechacek
2019-10-25 19:00 ` [PATCH v4 2/3] PCI: pciehp: Wait for PDS if in-band presence is disabled Stuart Hayes
2019-10-25 19:16 ` Andy Shevchenko [this message]
2019-10-25 19:00 ` [PATCH v4 3/3] PCI: pciehp: Add dmi table for in-band presence disabled Stuart Hayes
2019-10-25 19:18 ` Andy Shevchenko
2020-02-21 5:21 ` Bjorn Helgaas
2020-02-21 17:46 ` Stuart Hayes
2019-10-28 11:31 ` [PATCH v4 0/3] PCI: pciehp: Do not turn off slot if presence comes up after link Mika Westerberg
2020-02-08 20:22 ` Lukas Wunner
2020-02-11 0:08 ` Bjorn Helgaas
2020-02-11 4:49 ` Lukas Wunner
2020-02-11 14:14 ` Bjorn Helgaas
2020-02-11 14:32 ` Lukas Wunner
2020-02-11 19:31 ` Bjorn Helgaas
2020-02-18 17:32 ` Bjorn Helgaas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAHp75Vd54iDEe0ucTW8Gz9Q6cDGnA88XcBMy9-C5P1QuLzDm0Q@mail.gmail.com \
--to=andy.shevchenko@gmail.com \
--cc=austin_bolen@dell.com \
--cc=bhelgaas@google.com \
--cc=gustavo@embeddedor.com \
--cc=keith.busch@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=lukas@wunner.de \
--cc=mika.westerberg@linux.intel.com \
--cc=mr.nuke.me@gmail.com \
--cc=okaya@kernel.org \
--cc=poza@codeaurora.org \
--cc=rafael.j.wysocki@intel.com \
--cc=stuart.w.hayes@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).