[PATCH v2 6/6] ACPI: scan: Take PCI device enumeration into account directly

["Rafael J. Wysocki" <rafael@kernel.org>]

From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>

The ACPI companions of PCI devices are associated with the corresponding
PCI devices before being processed by acpi_scan_attach() and by the time
they are passed to attach_subtree(), the PCI devices associated with
them have been already enumerated and initialized.

Accordingly, it is not necessary or even useful to check their status in
attach_subtree(), so do not do that.

Fixes: 2c22e6520ac8 ("ACPI / scan: Use direct recurrence for device hierarchy walks")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Peixin Xie <peixin.xie@linux.spacemit.com>
---

v1 -> v2:
   * Use pci_name() (Andy)
   * Add tag from Peixin Xie

---
 drivers/acpi/scan.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index f4718b0207e0..34f7f477a25a 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -20,6 +20,7 @@
 #include <linux/kthread.h>
 #include <linux/dmi.h>
 #include <linux/dma-map-ops.h>
+#include <linux/pci.h>
 #include <linux/platform_data/x86/apple.h>
 #include <linux/pgtable.h>
 #include <linux/crc32.h>
@@ -2342,6 +2343,7 @@ static int acpi_scan_attach_handler(struct acpi_device *device)
 
 static int attach_subtree(struct acpi_device *device, void *not_used)
 {
+	struct pci_dev *pci;
 	acpi_handle ejd;
 	bool skip;
 	int ret;
@@ -2353,10 +2355,26 @@ static int attach_subtree(struct acpi_device *device, void *not_used)
 	if (ACPI_SUCCESS(acpi_bus_get_ejd(device->handle, &ejd)))
 		register_dock_dependent_device(device, ejd);
 
-	acpi_bus_get_status(device);
-	/* Skip devices that are not ready for enumeration (e.g. not present) */
-	if (!acpi_dev_ready_for_enumeration(device))
-		return 0;
+	/*
+	 * If the given ACPI device object has been already associated with a
+	 * PCI device found on the bus, its status is effectively "present
+	 * and functional".
+	 */
+	pci = acpi_dev_get_pci_dev(device);
+	if (pci) {
+		acpi_handle_debug(device->handle, "PCI companion %s found\n",
+				  pci_name(pci));
+
+		pci_dev_put(pci);
+	} else {
+		acpi_bus_get_status(device);
+		/*
+		 * Skip devices that are not ready for enumeration (e.g. not
+		 * present).
+		 */
+		if (!acpi_dev_ready_for_enumeration(device))
+			return 0;
+	}
 
 	acpi_ec_register_opregions(device);
 
-- 
2.51.0