linux-kernel - [PATCH 3.16 051/366] ACPI / hotplug / PCI: Check presence of slot itself in get_slot

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Message-ID: <lsq.1539530740.145069661@decadent.org.uk>
Date:   Sun, 14 Oct 2018 16:25:40 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Mika Westerberg" <mika.westerberg@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>,
        "Mike Lothian" <mike@...eburn.co.uk>
Subject: [PATCH 3.16 051/366] ACPI / hotplug / PCI: Check presence of slot
 itself in get_slot_status()

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Mika Westerberg <mika.westerberg@...ux.intel.com>

commit 13d3047c81505cc0fb9bdae7810676e70523c8bf upstream.

Mike Lothian reported that plugging in a USB-C device does not work
properly in his Dell Alienware system.  This system has an 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 is 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 (RP01)
but that seems to be incorrect because device 0 is the upstream port of the
Alpine Ridge PCIe switch and it has no functions other 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.  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 IDs of devices on PCI buses.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=198557
Reported-by: Mike Lothian <mike@...eburn.co.uk>
Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/pci/hotplug/acpiphp_glue.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -601,6 +601,7 @@ static unsigned int get_slot_status(stru
 {
 	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) {
@@ -611,19 +612,27 @@ static unsigned int get_slot_status(stru
 			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;
 }