PCI/MSI: Use FIELD_GET/PREP()

Instead of custom masking and shifting, use FIELD_GET/PREP() with
register fields.

Link: https://lore.kernel.org/r/20231018113254.17616-8-ilpo.jarvinen@linux.intel.comSigned-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/msi/msi.c

@@ -6,6 +6,7 @@
  * Copyright (C) Tom Long Nguyen (tom.l.nguyen@intel.com)
  * Copyright (C) 2016 Christoph Hellwig.
  */
+#include <linux/bitfield.h>
 #include <linux/err.h>
 #include <linux/export.h>
 #include <linux/irq.h>
@@ -188,7 +189,7 @@ static inline void pci_write_msg_msi(struct pci_dev *dev, struct msi_desc *desc,
 
 	pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &msgctl);
 	msgctl &= ~PCI_MSI_FLAGS_QSIZE;
-	msgctl |= desc->pci.msi_attrib.multiple << 4;
+	msgctl |= FIELD_PREP(PCI_MSI_FLAGS_QSIZE, desc->pci.msi_attrib.multiple);
 	pci_write_config_word(dev, pos + PCI_MSI_FLAGS, msgctl);
 
 	pci_write_config_dword(dev, pos + PCI_MSI_ADDRESS_LO, msg->address_lo);
@@ -299,7 +300,7 @@ static int msi_setup_msi_desc(struct pci_dev *dev, int nvec,
 	desc.pci.msi_attrib.is_64	= !!(control & PCI_MSI_FLAGS_64BIT);
 	desc.pci.msi_attrib.can_mask	= !!(control & PCI_MSI_FLAGS_MASKBIT);
 	desc.pci.msi_attrib.default_irq	= dev->irq;
-	desc.pci.msi_attrib.multi_cap	= (control & PCI_MSI_FLAGS_QMASK) >> 1;
+	desc.pci.msi_attrib.multi_cap	= FIELD_GET(PCI_MSI_FLAGS_QMASK, control);
 	desc.pci.msi_attrib.multiple	= ilog2(__roundup_pow_of_two(nvec));
 	desc.affinity			= masks;
 
@@ -478,7 +479,7 @@ int pci_msi_vec_count(struct pci_dev *dev)
 		return -EINVAL;
 
 	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &msgctl);
-	ret = 1 << ((msgctl & PCI_MSI_FLAGS_QMASK) >> 1);
+	ret = 1 << FIELD_GET(PCI_MSI_FLAGS_QMASK, msgctl);
 
 	return ret;
 }
@@ -511,7 +512,8 @@ void __pci_restore_msi_state(struct pci_dev *dev)
 	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
 	pci_msi_update_mask(entry, 0, 0);
 	control &= ~PCI_MSI_FLAGS_QSIZE;
-	control |= (entry->pci.msi_attrib.multiple << 4) | PCI_MSI_FLAGS_ENABLE;
+	control |= PCI_MSI_FLAGS_ENABLE |
+		   FIELD_PREP(PCI_MSI_FLAGS_QSIZE, entry->pci.msi_attrib.multiple);
 	pci_write_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, control);
 }