From: Sean O. Stalley <sean.stalley@intel.com>
Date: Thu, 2 Apr 2015 21:10:19 +0000 (-0700)
Subject: PCI: Read capability list as dwords, not bytes
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=55db3208f238ee776f1f747734051723d8a3c13e;p=deliverable%2Flinux.git

PCI: Read capability list as dwords, not bytes

Reading both the capability ID and "next" pointer at the same time lets us
parse the list with half the number of config reads.

Signed-off-by: Sean O. Stalley <sean.stalley@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 81f06e8dcc04..3c84cc6bc75a 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -145,19 +145,22 @@ static int __pci_find_next_cap_ttl(struct pci_bus *bus, unsigned int devfn,
 				   u8 pos, int cap, int *ttl)
 {
 	u8 id;
+	u16 ent;
+
+	pci_bus_read_config_byte(bus, devfn, pos, &pos);
 
 	while ((*ttl)--) {
-		pci_bus_read_config_byte(bus, devfn, pos, &pos);
 		if (pos < 0x40)
 			break;
 		pos &= ~3;
-		pci_bus_read_config_byte(bus, devfn, pos + PCI_CAP_LIST_ID,
-					 &id);
+		pci_bus_read_config_word(bus, devfn, pos, &ent);
+
+		id = ent & 0xff;
 		if (id == 0xff)
 			break;
 		if (id == cap)
 			return pos;
-		pos += PCI_CAP_LIST_NEXT;
+		pos = (ent >> 8);
 	}
 	return 0;
 }