i2c: i801: Use MMIO if available

Newer versions of supported chips support MMIO in addition to legacy
PMIO register access. Probe the MMIO PCI BAR and use faster MMIO
register access if available.

Signed-off-by: Heiner Kallweit <[email protected]>
Signed-off-by: Andi Shyti <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: hkallweit

drivers/i2c/busses/i2c-i801.c

@@ -144,6 +144,7 @@
 #define SMBNTFDADD(p)	(20 + (p)->smba)	/* ICH3 and later */
 
 /* PCI Address Constants */
+#define SMBBAR_MMIO	0
 #define SMBBAR		4
 #define SMBHSTCFG	0x040
 #define TCOBASE		0x050
@@ -1522,7 +1523,7 @@ static void i801_restore_regs(struct i801_priv *priv)
 
 static int i801_probe(struct pci_dev *dev, const struct pci_device_id *id)
 {
-	int err, i;
+	int err, i, bar = SMBBAR;
 	struct i801_priv *priv;
 
 	priv = devm_kzalloc(&dev->dev, sizeof(*priv), GFP_KERNEL);
@@ -1570,10 +1571,13 @@ static int i801_probe(struct pci_dev *dev, const struct pci_device_id *id)
 	if (i801_acpi_probe(priv))
 		return -ENODEV;
 
-	priv->smba = pcim_iomap_region(dev, SMBBAR, DRV_NAME);
+	if (pci_resource_flags(dev, SMBBAR_MMIO) & IORESOURCE_MEM)
+		bar = SMBBAR_MMIO;
+
+	priv->smba = pcim_iomap_region(dev, bar, DRV_NAME);
 	if (IS_ERR(priv->smba)) {
 		pci_err(dev, "Failed to request SMBus region %pr\n",
-			pci_resource_n(dev, SMBBAR));
+			pci_resource_n(dev, bar));
 		i801_acpi_remove(priv);
 		return PTR_ERR(priv->smba);
 	}