On Thu, Feb 22, 2018 at 09:19:24AM +0000, Mike Lothian wrote:
> On 12 February 2018 at 15:21, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> > On Mon, Feb 12, 2018 at 11:08:55AM +0000, Mike Lothian wrote:
> >> On 12 February 2018 at 10:55, Mika Westerberg
> >> <mika.westerberg@xxxxxxxxxxxxxxx> wrote:
> >> > Mike Lothian reported that plugging in a USB-C device does not work
> >> > properly in his Dell Alienware system. This system has Intel Alpine
> >> > Ridge Thunderbolt controller providing USB-C functionality. In these
> >> > systems the USB controller (xHCI) is hotplugged whenever a device is
> >> > connected to the port using ACPI based hotplug.
> >> >
> >> > The ACPI description of the root port in question looks as follows:
> >> >
> >> > Device (RP01)
> >> > {
> >> > Name (_ADR, 0x001C0000)
> >> >
> >> > Device (PXSX)
> >> > {
> >> > Name (_ADR, 0x02)
> >> >
> >> > Method (_RMV, 0, NotSerialized)
> >> > {
> >> > // ...
> >> > }
> >> > }
> >> >
> >> > Here _ADR 0x02 means device 0, function 2 on the bus under root port
> >> > (RP1) but that seems to be incorrect because device 0 is the upstream
> >> > port of the Alpine Ridge PCIe switch and it does not have other
> >> > functions than 0 (the bridge itself). When we get ACPI Notify() to the
> >> > root port resulting from connecting a USB-C device, Linux tries to read
> >> > PCI_VENDOR_ID from device 0, function 2 which of course always returns
> >> > 0xffffffff because there is no such function and we never find the
> >> > device.
> >> >
> >> > In Windows this works fine.
> >> >
> >> > Now, since we get ACPI Notify() to the root port and not to the PXSX
> >> > device we should actually start our scan from there as well and not from
> >> > the non-existent PXSX device so fix this by checking presence of the
> >> > slot itself (function 0) if we fail to do that otherwise.
> >> >
> >> > While there use pci_bus_read_dev_vendor_id() in get_slot_status() which
> >> > is the recommended way to read device and vendor ID of device on PCI bus.
> >> >
> >> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=198557
> >> > Reported-by: Mike Lothian <mike@xxxxxxxxxxxxxx>
> >> > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> >> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> >> > Cc: stable@xxxxxxxxxxxxxxx
> >> > ---
> >> > drivers/pci/hotplug/acpiphp_glue.c | 23 ++++++++++++++++-------
> >> > 1 file changed, 16 insertions(+), 7 deletions(-)
> >> >
> >> > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> >> > index e2198a2feeca..b45b375c0e6c 100644
> >> > --- a/drivers/pci/hotplug/acpiphp_glue.c
> >> > +++ b/drivers/pci/hotplug/acpiphp_glue.c
> >> > @@ -541,6 +541,7 @@ static unsigned int get_slot_status(struct acpiphp_slot *slot)
> >> > {
> >> > unsigned long long sta = 0;
> >> > struct acpiphp_func *func;
> >> > + u32 dvid;
> >> >
> >> > list_for_each_entry(func, &slot->funcs, sibling) {
> >> > if (func->flags & FUNC_HAS_STA) {
> >> > @@ -551,19 +552,27 @@ static unsigned int get_slot_status(struct acpiphp_slot *slot)
> >> > if (ACPI_SUCCESS(status) && sta)
> >> > break;
> >> > } else {
> >> > - u32 dvid;
> >> > -
> >> > - pci_bus_read_config_dword(slot->bus,
> >> > - PCI_DEVFN(slot->device,
> >> > - func->function),
> >> > - PCI_VENDOR_ID, &dvid);
> >> > - if (dvid != 0xffffffff) {
> >> > + if (pci_bus_read_dev_vendor_id(slot->bus,
> >> > + PCI_DEVFN(slot->device, func->function),
> >> > + &dvid, 0)) {
> >> > sta = ACPI_STA_ALL;
> >> > break;
> >> > }
> >> > }
> >> > }
> >> >
> >> > + if (!sta) {
> >> > + /*
> >> > + * Check for the slot itself since it may be that the
> >> > + * ACPI slot is a device below PCIe upstream port so in
> >> > + * that case it may not even be reachable yet.
> >> > + */
> >> > + if (pci_bus_read_dev_vendor_id(slot->bus,
> >> > + PCI_DEVFN(slot->device, 0), &dvid, 0)) {
> >> > + sta = ACPI_STA_ALL;
> >> > + }
> >> > + }
> >> > +
> >> > return (unsigned int)sta;
> >> > }
> >> >
> >> > --
> >> > 2.15.1
> >> >
> >>
> >> Thanks for this, it fixes a few other issues on my machine too
> >
> > Thanks for testing this. Can you elaborate on what other issues this
> > fixes? I don't know what they are, but they might be worth mentioning
> > in the changelog do make this fix more discoverable.
> >
> >> I'm going to do some searches around different bugzillas for the USB-C
> >> non-detection and the NVMe drive disappearing after suspend issues and
> >> report that they'll be getting a fix soon
> >
> > If you find more bugzillas that are fixed by this, please include the
> > URLs so we can include them in the changelog. (I can do this; no need
> > to respin the patch just for this.)
> >
> >> Tested-by: Mike Lothian <mike@xxxxxxxxxxxxxx>
> >> --
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>
> Hi
>
> Is this going in via this tree:
> https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/
>
> Is there anything else that needs to be done before it can go into rc3?
Not on your end. But thanks fo the reminder, and also for the hint
that you'd like it in -rc3. It's not likely to make -rc3 because I
like things to at least be in -next for a few days before I ask Linus
to pull them.
But more importantly, what's the justification for adding this after
the merge window? It doesn't look like a regression or a fix for
something we broke in the merge window. It certainly *could* still be
merged for v4.16, but the default target would be v4.17.
Bjorn
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