i2c: piix4: Add EFCH MMIO support for SMBus port select

AMD processors include registers capable of selecting between 2 SMBus
ports. Port selection is made during each user access by writing to
FCH::PM::DECODEEN[smbus0sel]. Change the driver to use MMIO during
SMBus port selection because cd6h/cd7h port I/O is not available on
later AMD processors.
Signed-off-by: Terry Bowman <terry.bowman@amd.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-piix4.c

@@ -753,10 +753,19 @@ static void piix4_imc_wakeup(void)
 	release_region(KERNCZ_IMC_IDX, 2);
 }
 
-static int piix4_sb800_port_sel(u8 port)
+static int piix4_sb800_port_sel(u8 port, struct sb800_mmio_cfg *mmio_cfg)
 {
 	u8 smba_en_lo, val;
 
+	if (mmio_cfg->use_mmio) {
+		smba_en_lo = ioread8(mmio_cfg->addr + piix4_port_sel_sb800);
+		val = (smba_en_lo & ~piix4_port_mask_sb800) | port;
+		if (smba_en_lo != val)
+			iowrite8(val, mmio_cfg->addr + piix4_port_sel_sb800);
+
+		return (smba_en_lo & piix4_port_mask_sb800);
+	}
+
 	outb_p(piix4_port_sel_sb800, SB800_PIIX4_SMB_IDX);
 	smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
 
@@ -843,12 +852,12 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
 		}
 	}
 
-	prev_port = piix4_sb800_port_sel(adapdata->port);
+	prev_port = piix4_sb800_port_sel(adapdata->port, &adapdata->mmio_cfg);
 
 	retval = piix4_access(adap, addr, flags, read_write,
 			      command, size, data);
 
-	piix4_sb800_port_sel(prev_port);
+	piix4_sb800_port_sel(prev_port, &adapdata->mmio_cfg);
 
 	/* Release the semaphore */
 	outb_p(smbslvcnt | 0x20, SMBSLVCNT);