PCI: pciehp: add ACPI based slot detection

There is a problem that some non hot-pluggable PCIe slots are detected
as hot-pluggable by pciehp on some platforms. The immediate cause of
this problem is that hot-plug capable bit in the Slot Capabilities
register is set even for non hot-pluggable slots on those platforms.
It seems a BIOS/hardware problem, but we need workaround about that.

Some of those platforms define hot-pluggable PCIe slots on ACPI
namespace properly, while hot-plug capable bit in the Slot
Capabilities register is set improperly. So using ACPI namespace
information in pciehp to detect PCIe hot-pluggable slots would be a
workaround.

This patch adds 'pciehp_detect_mode' module option. When 'acpi' is
specified, pciehp uses ACPI namespace information to detect PCIe
hot-pluggable slots.

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 114 insertions, 0 deletions

diff --git a/drivers/pci/hotplug/pciehp_acpi.c b/drivers/pci/hotplug/pciehp_acpi.c
new file mode 100644
index 0000000..0cd49b7
--- /dev/null
+++ b/drivers/pci/hotplug/pciehp_acpi.c
@@ -0,0 +1,114 @@
+/*
+ * ACPI related functions for PCI Express Hot Plug driver.
+ *
+ * Copyright (C) 2008 Kenji Kaneshige
+ * Copyright (C) 2008 Fujitsu Limited.
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#include <linux/acpi.h>
+#include "pciehp.h"
+
+#define PCIEHP_DETECT_PCIE	(0)
+#define PCIEHP_DETECT_ACPI	(1)
+#define PCIEHP_DETECT_DEFAULT	PCIEHP_DETECT_PCIE
+
+static int slot_detection_mode;
+static char *pciehp_detect_mode;
+module_param(pciehp_detect_mode, charp, 0444);
+MODULE_PARM_DESC(pciehp_detect_mode,
+		 "Slot detection mode: pcie, acpi\n"
+		 "  pcie - Use PCIe based slot detection (default)\n"
+		 "  acpi - Use ACPI for slot detection\n");
+
+static int is_ejectable(acpi_handle handle)
+{
+	acpi_status status;
+	acpi_handle tmp;
+	unsigned long long removable;
+	status = acpi_get_handle(handle, "_ADR", &tmp);
+	if (ACPI_FAILURE(status))
+		return 0;
+	status = acpi_get_handle(handle, "_EJ0", &tmp);
+	if (ACPI_SUCCESS(status))
+		return 1;
+	status = acpi_evaluate_integer(handle, "_RMV", NULL, &removable);
+	if (ACPI_SUCCESS(status) && removable)
+		return 1;
+	return 0;
+}
+
+static acpi_status
+check_hotplug(acpi_handle handle, u32 lvl, void *context, void **rv)
+{
+	int *found = (int *)context;
+	if (is_ejectable(handle)) {
+		*found = 1;
+		return AE_CTRL_TERMINATE;
+	}
+	return AE_OK;
+}
+
+static int pciehp_detect_acpi_slot(struct pci_bus *pbus)
+{
+	acpi_handle handle;
+	struct pci_dev *pdev = pbus->self;
+	int found = 0;
+
+	if (!pdev){
+		int seg = pci_domain_nr(pbus), busnr = pbus->number;
+		handle = acpi_get_pci_rootbridge_handle(seg, busnr);
+	} else
+		handle = DEVICE_ACPI_HANDLE(&(pdev->dev));
+
+	if (!handle)
+		return 0;
+
+	acpi_walk_namespace(ACPI_TYPE_DEVICE, handle, (u32)1,
+			    check_hotplug, (void *)&found, NULL);
+	return found;
+}
+
+int pciehp_acpi_slot_detection_check(struct pci_dev *dev)
+{
+	if (slot_detection_mode != PCIEHP_DETECT_ACPI)
+		return 0;
+	if (pciehp_detect_acpi_slot(dev->subordinate))
+		return 0;
+	return -ENODEV;
+}
+
+static int __init parse_detect_mode(void)
+{
+	if (!pciehp_detect_mode)
+		return PCIEHP_DETECT_DEFAULT;
+	if (!strcmp(pciehp_detect_mode, "pcie"))
+		return PCIEHP_DETECT_PCIE;
+	if (!strcmp(pciehp_detect_mode, "acpi"))
+		return PCIEHP_DETECT_ACPI;
+	warn("bad specifier '%s' for pciehp_detect_mode. Use default\n",
+	     pciehp_detect_mode);
+	return PCIEHP_DETECT_DEFAULT;
+}
+
+void __init pciehp_acpi_slot_detection_init(void)
+{
+	slot_detection_mode = parse_detect_mode();
+}