struct asic3 *asic = platform_get_drvdata(pdev);
        unsigned long clksel = 0;
        unsigned int irq, irq_base;
+       int map_size;
 
        asic->irq_nr = platform_get_irq(pdev, 0);
        if (asic->irq_nr < 0)
                goto out_free;
        }
 
-
-       asic->mapping = ioremap(mem->start, PAGE_SIZE);
+       map_size = mem->end - mem->start + 1;
+       asic->mapping = ioremap(mem->start, map_size);
        if (!asic->mapping) {
                ret = -ENOMEM;
                dev_err(asic->dev, "Couldn't ioremap\n");
 
        asic->irq_base = pdata->irq_base;
 
-       if (pdata && pdata->bus_shift)
-               asic->bus_shift = 2 - pdata->bus_shift;
-       else
-               asic->bus_shift = 0;
+       /* calculate bus shift from mem resource */
+       asic->bus_shift = 2 - (map_size >> 12);
 
        clksel = 0;
        asic3_write_register(asic, ASIC3_OFFSET(CLOCK, SEL), clksel);
 
        u16 *gpio_config;
        unsigned int gpio_config_num;
 
-       unsigned int bus_shift;
-
        unsigned int irq_base;
 
        unsigned int gpio_base;
 #define ASIC3_SDIO_CTRL_LEDCtrl              0x7C
 #define ASIC3_SDIO_CTRL_SoftwareReset        0x1C0
 
-#define ASIC3_MAP_SIZE                      0x2000
+#define ASIC3_MAP_SIZE_32BIT   0x2000
+#define ASIC3_MAP_SIZE_16BIT   0x1000
 
 #endif /* __ASIC3_H__ */