diff --git a/drivers/mfd/tqmx86.c b/drivers/mfd/tqmx86.c
index 732013f40e4e..99a59341e449 100644
--- a/drivers/mfd/tqmx86.c
+++ b/drivers/mfd/tqmx86.c
@@ -45,9 +45,8 @@
 #define TQMX86_REG_IO_EXT_INT_MASK		0x3
 #define TQMX86_REG_IO_EXT_INT_GPIO_SHIFT	4
 
-#define TQMX86_REG_I2C_DETECT	0x47
+#define TQMX86_REG_I2C_DETECT	0x1a7
 #define TQMX86_REG_I2C_DETECT_SOFT		0xa5
-#define TQMX86_REG_I2C_INT_EN	0x49
 
 static uint gpio_irq;
 module_param(gpio_irq, uint, 0);
@@ -195,7 +194,12 @@ static int tqmx86_probe(struct platform_device *pdev)
 		 "Found %s - Board ID %d, PCB Revision %d, PLD Revision %d\n",
 		 board_name, board_id, rev >> 4, rev & 0xf);
 
-	i2c_det = ioread8(io_base + TQMX86_REG_I2C_DETECT);
+	/*
+	 * The I2C_DETECT register is in the range assigned to the I2C driver
+	 * later, so we don't extend TQMX86_IOSIZE. Use inb() for this one-off
+	 * access instead of ioport_map + unmap.
+	 */
+	i2c_det = inb(TQMX86_REG_I2C_DETECT);
 
 	if (gpio_irq_cfg) {
 		io_ext_int_val =