diff --git a/drivers/net/fddi/Kconfig b/drivers/net/fddi/Kconfig
index f722079dfb6aea7b495952aa7ce7a53cd8feefb5..846bf41c27178ad8766a34a9418cf3be674d5322 100644
--- a/drivers/net/fddi/Kconfig
+++ b/drivers/net/fddi/Kconfig
@@ -38,22 +38,6 @@ config DEFXX
 	  To compile this driver as a module, choose M here: the module
 	  will be called defxx.  If unsure, say N.
 
-config DEFXX_MMIO
-	bool
-	prompt "Use MMIO instead of PIO" if PCI || EISA
-	depends on DEFXX
-	default n if PCI || EISA
-	default y
-	help
-	  This instructs the driver to use EISA or PCI memory-mapped I/O
-	  (MMIO) as appropriate instead of programmed I/O ports (PIO).
-	  Enabling this gives an improvement in processing time in parts
-	  of the driver, but it may cause problems with EISA (DEFEA)
-	  adapters.  TURBOchannel does not have the concept of I/O ports,
-	  so MMIO is always used for these (DEFTA) adapters.
-
-	  If unsure, say N.
-
 config SKFP
 	tristate "SysKonnect FDDI PCI support"
 	depends on FDDI && PCI
diff --git a/drivers/net/fddi/defxx.c b/drivers/net/fddi/defxx.c
index 98302356dcb4a591e345642a7fed46dab4fefabc..6d1e3f49a3d3daa9f46f1dfbd529d940850e7ab6 100644
--- a/drivers/net/fddi/defxx.c
+++ b/drivers/net/fddi/defxx.c
@@ -197,6 +197,7 @@
  *		23 Oct 2006	macro		Big-endian host support.
  *		14 Dec 2006	macro		TURBOchannel support.
  *		01 Jul 2014	macro		Fixes for DMA on 64-bit hosts.
+ *		10 Mar 2021	macro		Dynamic MMIO vs port I/O.
  */
 
 /* Include files */
@@ -225,8 +226,8 @@
 
 /* Version information string should be updated prior to each new release!  */
 #define DRV_NAME "defxx"
-#define DRV_VERSION "v1.11"
-#define DRV_RELDATE "2014/07/01"
+#define DRV_VERSION "v1.12"
+#define DRV_RELDATE "2021/03/10"
 
 static const char version[] =
 	DRV_NAME ": " DRV_VERSION " " DRV_RELDATE
@@ -253,10 +254,10 @@ static const char version[] =
 #define DFX_BUS_TC(dev) 0
 #endif
 
-#ifdef CONFIG_DEFXX_MMIO
-#define DFX_MMIO 1
+#if defined(CONFIG_EISA) || defined(CONFIG_PCI)
+#define dfx_use_mmio bp->mmio
 #else
-#define DFX_MMIO 0
+#define dfx_use_mmio true
 #endif
 
 /* Define module-wide (static) routines */
@@ -374,8 +375,6 @@ static inline void dfx_outl(DFX_board_t *bp, int offset, u32 data)
 static void dfx_port_write_long(DFX_board_t *bp, int offset, u32 data)
 {
 	struct device __maybe_unused *bdev = bp->bus_dev;
-	int dfx_bus_tc = DFX_BUS_TC(bdev);
-	int dfx_use_mmio = DFX_MMIO || dfx_bus_tc;
 
 	if (dfx_use_mmio)
 		dfx_writel(bp, offset, data);
@@ -398,8 +397,6 @@ static inline void dfx_inl(DFX_board_t *bp, int offset, u32 *data)
 static void dfx_port_read_long(DFX_board_t *bp, int offset, u32 *data)
 {
 	struct device __maybe_unused *bdev = bp->bus_dev;
-	int dfx_bus_tc = DFX_BUS_TC(bdev);
-	int dfx_use_mmio = DFX_MMIO || dfx_bus_tc;
 
 	if (dfx_use_mmio)
 		dfx_readl(bp, offset, data);
@@ -421,7 +418,7 @@ static void dfx_port_read_long(DFX_board_t *bp, int offset, u32 *data)
  *   None
  *
  * Arguments:
- *   bdev	- pointer to device information
+ *   bp		- pointer to board information
  *   bar_start	- pointer to store the start addresses
  *   bar_len	- pointer to store the lengths of the areas
  *
@@ -431,13 +428,13 @@ static void dfx_port_read_long(DFX_board_t *bp, int offset, u32 *data)
  * Side Effects:
  *   None
  */
-static void dfx_get_bars(struct device *bdev,
+static void dfx_get_bars(DFX_board_t *bp,
 			 resource_size_t *bar_start, resource_size_t *bar_len)
 {
+	struct device *bdev = bp->bus_dev;
 	int dfx_bus_pci = dev_is_pci(bdev);
 	int dfx_bus_eisa = DFX_BUS_EISA(bdev);
 	int dfx_bus_tc = DFX_BUS_TC(bdev);
-	int dfx_use_mmio = DFX_MMIO || dfx_bus_tc;
 
 	if (dfx_bus_pci) {
 		int num = dfx_use_mmio ? 0 : 1;
@@ -495,6 +492,13 @@ static const struct net_device_ops dfx_netdev_ops = {
 	.ndo_set_mac_address	= dfx_ctl_set_mac_address,
 };
 
+static void dfx_register_res_err(const char *print_name, bool mmio,
+				 unsigned long start, unsigned long len)
+{
+	pr_err("%s: Cannot reserve %s resource 0x%lx @ 0x%lx, aborting\n",
+	       print_name, mmio ? "MMIO" : "I/O", len, start);
+}
+
 /*
  * ================
  * = dfx_register =
@@ -528,8 +532,6 @@ static int dfx_register(struct device *bdev)
 	static int version_disp;
 	int dfx_bus_pci = dev_is_pci(bdev);
 	int dfx_bus_eisa = DFX_BUS_EISA(bdev);
-	int dfx_bus_tc = DFX_BUS_TC(bdev);
-	int dfx_use_mmio = DFX_MMIO || dfx_bus_tc;
 	const char *print_name = dev_name(bdev);
 	struct net_device *dev;
 	DFX_board_t	  *bp;			/* board pointer */
@@ -567,46 +569,48 @@ static int dfx_register(struct device *bdev)
 	bp->bus_dev = bdev;
 	dev_set_drvdata(bdev, dev);
 
-	dfx_get_bars(bdev, bar_start, bar_len);
-	if (dfx_bus_eisa && dfx_use_mmio && bar_start[0] == 0) {
-		pr_err("%s: Cannot use MMIO, no address set, aborting\n",
-		       print_name);
-		pr_err("%s: Run ECU and set adapter's MMIO location\n",
-		       print_name);
-		pr_err("%s: Or recompile driver with \"CONFIG_DEFXX_MMIO=n\""
-		       "\n", print_name);
-		err = -ENXIO;
-		goto err_out;
+	bp->mmio = true;
+
+	dfx_get_bars(bp, bar_start, bar_len);
+	if (bar_len[0] == 0 ||
+	    (dfx_bus_eisa && dfx_use_mmio && bar_start[0] == 0)) {
+		bp->mmio = false;
+		dfx_get_bars(bp, bar_start, bar_len);
 	}
 
-	if (dfx_use_mmio)
+	if (dfx_use_mmio) {
 		region = request_mem_region(bar_start[0], bar_len[0],
-					    print_name);
-	else
-		region = request_region(bar_start[0], bar_len[0], print_name);
+					    bdev->driver->name);
+		if (!region && (dfx_bus_eisa || dfx_bus_pci)) {
+			bp->mmio = false;
+			dfx_get_bars(bp, bar_start, bar_len);
+		}
+	}
+	if (!dfx_use_mmio)
+		region = request_region(bar_start[0], bar_len[0],
+					bdev->driver->name);
 	if (!region) {
-		pr_err("%s: Cannot reserve %s resource 0x%lx @ 0x%lx, "
-		       "aborting\n", dfx_use_mmio ? "MMIO" : "I/O", print_name,
-		       (long)bar_len[0], (long)bar_start[0]);
+		dfx_register_res_err(print_name, dfx_use_mmio,
+				     bar_start[0], bar_len[0]);
 		err = -EBUSY;
 		goto err_out_disable;
 	}
 	if (bar_start[1] != 0) {
-		region = request_region(bar_start[1], bar_len[1], print_name);
+		region = request_region(bar_start[1], bar_len[1],
+					bdev->driver->name);
 		if (!region) {
-			pr_err("%s: Cannot reserve I/O resource "
-			       "0x%lx @ 0x%lx, aborting\n", print_name,
-			       (long)bar_len[1], (long)bar_start[1]);
+			dfx_register_res_err(print_name, 0,
+					     bar_start[1], bar_len[1]);
 			err = -EBUSY;
 			goto err_out_csr_region;
 		}
 	}
 	if (bar_start[2] != 0) {
-		region = request_region(bar_start[2], bar_len[2], print_name);
+		region = request_region(bar_start[2], bar_len[2],
+					bdev->driver->name);
 		if (!region) {
-			pr_err("%s: Cannot reserve I/O resource "
-			       "0x%lx @ 0x%lx, aborting\n", print_name,
-			       (long)bar_len[2], (long)bar_start[2]);
+			dfx_register_res_err(print_name, 0,
+					     bar_start[2], bar_len[2]);
 			err = -EBUSY;
 			goto err_out_bh_region;
 		}
@@ -721,7 +725,6 @@ static void dfx_bus_init(struct net_device *dev)
 	int dfx_bus_pci = dev_is_pci(bdev);
 	int dfx_bus_eisa = DFX_BUS_EISA(bdev);
 	int dfx_bus_tc = DFX_BUS_TC(bdev);
-	int dfx_use_mmio = DFX_MMIO || dfx_bus_tc;
 	u8 val;
 
 	DBG_printk("In dfx_bus_init...\n");
@@ -1041,7 +1044,6 @@ static int dfx_driver_init(struct net_device *dev, const char *print_name,
 	int dfx_bus_pci = dev_is_pci(bdev);
 	int dfx_bus_eisa = DFX_BUS_EISA(bdev);
 	int dfx_bus_tc = DFX_BUS_TC(bdev);
-	int dfx_use_mmio = DFX_MMIO || dfx_bus_tc;
 	int alloc_size;			/* total buffer size needed */
 	char *top_v, *curr_v;		/* virtual addrs into memory block */
 	dma_addr_t top_p, curr_p;	/* physical addrs into memory block */
@@ -3695,8 +3697,6 @@ static void dfx_unregister(struct device *bdev)
 	struct net_device *dev = dev_get_drvdata(bdev);
 	DFX_board_t *bp = netdev_priv(dev);
 	int dfx_bus_pci = dev_is_pci(bdev);
-	int dfx_bus_tc = DFX_BUS_TC(bdev);
-	int dfx_use_mmio = DFX_MMIO || dfx_bus_tc;
 	resource_size_t bar_start[3] = {0};	/* pointers to ports */
 	resource_size_t bar_len[3] = {0};	/* resource lengths */
 	int		alloc_size;		/* total buffer size used */
@@ -3716,7 +3716,7 @@ static void dfx_unregister(struct device *bdev)
 
 	dfx_bus_uninit(dev);
 
-	dfx_get_bars(bdev, bar_start, bar_len);
+	dfx_get_bars(bp, bar_start, bar_len);
 	if (bar_start[2] != 0)
 		release_region(bar_start[2], bar_len[2]);
 	if (bar_start[1] != 0)
@@ -3748,7 +3748,7 @@ static const struct pci_device_id dfx_pci_table[] = {
 MODULE_DEVICE_TABLE(pci, dfx_pci_table);
 
 static struct pci_driver dfx_pci_driver = {
-	.name		= "defxx",
+	.name		= DRV_NAME,
 	.id_table	= dfx_pci_table,
 	.probe		= dfx_pci_register,
 	.remove		= dfx_pci_unregister,
@@ -3779,7 +3779,7 @@ MODULE_DEVICE_TABLE(eisa, dfx_eisa_table);
 static struct eisa_driver dfx_eisa_driver = {
 	.id_table	= dfx_eisa_table,
 	.driver		= {
-		.name	= "defxx",
+		.name	= DRV_NAME,
 		.bus	= &eisa_bus_type,
 		.probe	= dfx_dev_register,
 		.remove	= dfx_dev_unregister,
@@ -3800,7 +3800,7 @@ MODULE_DEVICE_TABLE(tc, dfx_tc_table);
 static struct tc_driver dfx_tc_driver = {
 	.id_table	= dfx_tc_table,
 	.driver		= {
-		.name	= "defxx",
+		.name	= DRV_NAME,
 		.bus	= &tc_bus_type,
 		.probe	= dfx_dev_register,
 		.remove	= dfx_dev_unregister,
diff --git a/drivers/net/fddi/defxx.h b/drivers/net/fddi/defxx.h
index 4c31d31e0a3fbe49273fe2efa1b4713de9cf261e..8193713e12db5f8b40818354fd031e9431701c48 100644
--- a/drivers/net/fddi/defxx.h
+++ b/drivers/net/fddi/defxx.h
@@ -27,6 +27,7 @@
  *		04 Aug 2003	macro		Converted to the DMA API.
  *		23 Oct 2006	macro		Big-endian host support.
  *		14 Dec 2006	macro		TURBOchannel support.
+ *		10 Mar 2021	macro		Dynamic MMIO vs port I/O.
  */
 
 #ifndef _DEFXX_H_
@@ -1776,6 +1777,8 @@ typedef struct DFX_board_tag
 		int port;
 	} base;										/* base address */
 	struct device			*bus_dev;
+	/* Whether to use MMIO or port I/O.  */
+	bool				mmio;
 	u32				full_duplex_enb;				/* FDDI Full Duplex enable (1 == on, 2 == off) */
 	u32				req_ttrt;					/* requested TTRT value (in 80ns units) */
 	u32				burst_size;					/* adapter burst size (enumerated) */