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References: <20220905065622.1573811-1-kai.heng.feng@canonical.com> <YxWgGKIAvsxwSz85@black.fi.intel.com>
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From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
Date:   Mon, 5 Sep 2022 15:26:28 +0800
Message-ID: <CAAd53p4iV=ne5bDGZ6FxE9bBUVoFh=eXF9_oMPvPzjVj=UVoog@mail.gmail.com>
Subject: Re: [PATCH] thunderbolt: Resume PCIe bridges after switch is found on
 AMD USB4 controller
To:     Mika Westerberg <mika.westerberg@linux.intel.com>
Cc:     andreas.noever@gmail.com, michael.jamet@intel.com,
        YehezkelShB@gmail.com, sanju.mehta@amd.com,
        mario.limonciello@amd.com, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Hi Mika,

On Mon, Sep 5, 2022 at 3:06 PM Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
>
> Hi,
>
> On Mon, Sep 05, 2022 at 02:56:22PM +0800, Kai-Heng Feng wrote:
> > AMD USB4 can not detect external PCIe devices like external NVMe when
> > it's hotplugged, because card/link are not up:
> >
> > pcieport 0000:00:04.1: pciehp: pciehp_check_link_active: lnk_status = 1101
>
> I think the correct solution is then to block them from runtime
> suspending entirely.

Do you mean disable runtime suspend completely? Or just block runtime
suspend for a period?

>
> > Use `lspci` to resume pciehp bridges can find external devices.
> >
> > A long delay before checking card/link presence doesn't help, either.
> > The only way to make the hotplug work is to enable pciehp interrupt and
> > check card presence after the TB switch is added.
> >
> > Since the topology of USB4 and its PCIe bridges are siblings, hardcode
> > the bridge ID so TBT driver can wake them up to check presence.
>
> Let's not add PCI things into TBT driver unless absolutely necessary.

OK. It's getting harder as different components are intertwined
together on new hardwares...

>
> At least on Intel hardware the PCIe hotplug is signaled by SCI when the
> root port is in D3, I wonder if AMD has something similar.

Yes those root ports are resumed to D0 when something is plugged. They
however fail to detect any externel PCIe devices.

Kai-Heng