diff -Nur linux-orig/arch/mips/au1000/mtx-2/board_setup.c linux-mtx-2-2.4.27-idsel-fix/linux/arch/mips/au1000/mtx-2/board_setup.c
--- linux-orig/arch/mips/au1000/mtx-2/board_setup.c	2006-05-26 12:39:00.000000000 +0200
+++ linux/arch/mips/au1000/mtx-2/board_setup.c	2006-06-02 17:50:09.000000000 +0200
@@ -46,8 +46,11 @@
 #include <asm/pgtable.h>
 #include <asm/au1000.h>
 
+static int mtx2_pci_idsel(unsigned int devsel, int assert);
+extern int (*board_pci_idsel)(unsigned int devsel, int assert);
+
 extern struct rtc_ops no_rtc_ops;
 
 void board_reset (void)
 {
 	/* Hit BCSR.SYSTEM_CONTROL[SW_RST] */
@@ -115,5 +118,31 @@
 	au_writel( au_readl(GPIO2_DIR) | 0x1800, GPIO2_DIR );
 	au_writel( 0x18000800, GPIO2_OUTPUT );
 #endif
+
+
+	board_pci_idsel = mtx2_pci_idsel;
+
 	printk("4G Systems MTX-2 Board\n");
 }
+
+
+static int mtx2_pci_idsel(unsigned int devsel, int assert)
+{
+#define MTX_IDSEL_ONLY_0_AND_3 0
+#if MTX_IDSEL_ONLY_0_AND_3
+	if (devsel != 0 && devsel != 3) {
+		printk("*** not 0 or 3\n");
+		return 0;
+	}
+#endif
+
+	if (assert && devsel != 0) {
+		// supress signal to cardbus
+		au_writel( (1<<(16+5)) | (0<<5), GPIO2_OUTPUT); // set EXT_IO3 OFF
+	}
+	else {
+		au_writel( (1<<(16+5)) | (1<<5), GPIO2_OUTPUT); // set EXT_IO3 ON
+	}
+	au_sync_udelay(1);
+	return 1;
+}