linux-kernel - Re: [PATCH] PCI: pciehp: Fix system hang on resume after hot-unplug during suspend

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Message-ID: <CAFv23Q=4O5czQaNw2mEnwkb9LQfODfQDeW+qQD14rfdeVEwjwA@mail.gmail.com>
Date: Mon, 7 Oct 2024 12:34:09 +0800
From: AceLan Kao <acelan.kao@...onical.com>
To: Lukas Wunner <lukas@...ner.de>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: pciehp: Fix system hang on resume after hot-unplug
 during suspend

Lukas Wunner <lukas@...ner.de> 於 2024年10月1日 週二 下午7:03寫道：
>
> On Tue, Oct 01, 2024 at 01:02:46PM +0200, Lukas Wunner wrote:
> > On Mon, Sep 30, 2024 at 09:31:53AM +0800, AceLan Kao wrote:
> > > Lukas Wunner <lukas@...ner.de> 2024 9 28 8:51:
> > > > -       if (pci_get_dsn(pdev) != ctrl->dsn)
> > > > +       dsn = pci_get_dsn(pdev);
> > > > +       if (!PCI_POSSIBLE_ERROR(dsn) &&
> > > > +           dsn != ctrl->dsn)
> > > >                 return true;
> > >
> > > In my case, the pciehp_device_replaced() returns true from this final check.
> > > And these are the values I got
> > > dsn = 0x00000000, ctrl->dsn = 0x7800AA00
> > > dsn = 0x00000000, ctrl->dsn = 0x21B7D000
> >
> > Ah because pci_get_dsn() returns 0 if the device is gone.
> > Below is a modified patch which returns false in that case.
>
> Sorry, forgot to include the patch:
>
> -- >8 --
>
> diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c
> index ff458e6..957c320 100644
> --- a/drivers/pci/hotplug/pciehp_core.c
> +++ b/drivers/pci/hotplug/pciehp_core.c
> @@ -287,24 +287,32 @@ static int pciehp_suspend(struct pcie_device *dev)
>  static bool pciehp_device_replaced(struct controller *ctrl)
>  {
>         struct pci_dev *pdev __free(pci_dev_put);
> +       u64 dsn;
>         u32 reg;
>
>         pdev = pci_get_slot(ctrl->pcie->port->subordinate, PCI_DEVFN(0, 0));
>         if (!pdev)
> +               return false;
> +
> +       if (pci_read_config_dword(pdev, PCI_VENDOR_ID, &reg) == 0 &&
> +           !PCI_POSSIBLE_ERROR(reg) &&
> +           reg != (pdev->vendor | (pdev->device << 16)))
>                 return true;
>
> -       if (pci_read_config_dword(pdev, PCI_VENDOR_ID, &reg) ||
> -           reg != (pdev->vendor | (pdev->device << 16)) ||
> -           pci_read_config_dword(pdev, PCI_CLASS_REVISION, &reg) ||
> +       if (pci_read_config_dword(pdev, PCI_CLASS_REVISION, &reg) == 0 &&
> +           !PCI_POSSIBLE_ERROR(reg) &&
>             reg != (pdev->revision | (pdev->class << 8)))
>                 return true;
>
>         if (pdev->hdr_type == PCI_HEADER_TYPE_NORMAL &&
> -           (pci_read_config_dword(pdev, PCI_SUBSYSTEM_VENDOR_ID, &reg) ||
> -            reg != (pdev->subsystem_vendor | (pdev->subsystem_device << 16))))
> +           pci_read_config_dword(pdev, PCI_SUBSYSTEM_VENDOR_ID, &reg) == 0 &&
> +           !PCI_POSSIBLE_ERROR(reg) &&
> +           reg != (pdev->subsystem_vendor | (pdev->subsystem_device << 16)))
>                 return true;
>
> -       if (pci_get_dsn(pdev) != ctrl->dsn)
> +       if ((dsn = pci_get_dsn(pdev)) &&
> +           !PCI_POSSIBLE_ERROR(dsn) &&
> +           dsn != ctrl->dsn)
>                 return true;
>
>         return false;
Hi Lukas,

Sorry for the late reply, just encountered a strong typhoon in my area
last week and can't check this in our lab.

The patched pciehp_device_replaced() returns false at the end of the
function in my case.
Unplug the dock which is connected with a tbt storage won't be
considered as a replacement.

But when I tried to replace the dock with the tbt storage during
suspend, it still returned false at the end of the function like
unplugged.

BTW, it's a new model, so I think the ICM is used. And the reg is
0xffffffff when unplugged.