PCI/PME: Use FIELD_GET()

Use FIELD_GET() to remove dependences on the field position, i.e., the
shift value.  No functional change intended.

Link: https://lore.kernel.org/r/20231010204436.1000644-8-helgaas@kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Author: bjorn-helgaas

drivers/pci/pcie/pme.c

@@ -9,6 +9,7 @@
 
 #define dev_fmt(fmt) "PME: " fmt
 
+#include <linux/bitfield.h>
 #include <linux/pci.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
@@ -235,7 +236,8 @@ static void pcie_pme_work_fn(struct work_struct *work)
 			pcie_clear_root_pme_status(port);
 
 			spin_unlock_irq(&data->lock);
-			pcie_pme_handle_request(port, rtsta & 0xffff);
+			pcie_pme_handle_request(port,
+				    FIELD_GET(PCI_EXP_RTSTA_PME_RQ_ID, rtsta));
 			spin_lock_irq(&data->lock);
 
 			continue;

include/uapi/linux/pci_regs.h

@@ -637,6 +637,7 @@
 #define PCI_EXP_RTCAP		0x1e	/* Root Capabilities */
 #define  PCI_EXP_RTCAP_CRSVIS	0x0001	/* CRS Software Visibility capability */
 #define PCI_EXP_RTSTA		0x20	/* Root Status */
+#define  PCI_EXP_RTSTA_PME_RQ_ID 0x0000ffff /* PME Requester ID */
 #define  PCI_EXP_RTSTA_PME	0x00010000 /* PME status */
 #define  PCI_EXP_RTSTA_PENDING	0x00020000 /* PME pending */
 /*