i2c: i801: Use MMIO if available

JIRA: https://issues.redhat.com/browse/RHEL-113184

commit d50f2f5
Author: Heiner Kallweit <hkallweit1@gmail.com>
Date:   Wed Mar 12 20:08:18 2025 +0100

    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 <hkallweit1@gmail.com>
    Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
    Link: https://lore.kernel.org/r/b4748b7a-aac5-445c-b813-20c4d2c23ec3@gmail.com

Signed-off-by: Steve Best <sbest@redhat.com>

Author: sfbest

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);
 	}