parisc: Add qemu fw_cfg interface

When running on qemu, SeaBIOS-hppa stores the iomem address for the
emulated fw_cfg port in PAGE0_>pad0[2/3]. Let the Linux driver
auto-configure the fw_cfg interface with it, so that the fw_cfg info
shows up in /sys/firmware/qemu_fw_cfg.
Signed-off-by: Helge Deller <deller@gmx.de>

arch/parisc/Kconfig

@@ -376,5 +376,6 @@ config KEXEC_FILE
 
 endmenu
 
+source "drivers/firmware/Kconfig"
 
 source "drivers/parisc/Kconfig"

arch/parisc/kernel/inventory.c

@@ -19,6 +19,7 @@
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
+#include <linux/platform_device.h>
 #include <asm/hardware.h>
 #include <asm/io.h>
 #include <asm/mmzone.h>
@@ -641,4 +642,33 @@ void __init do_device_inventory(void)
 	if (pa_serialize_tlb_flushes)
 		pr_info("Merced bus found: Enable PxTLB serialization.\n");
 #endif
+
+#if defined(CONFIG_FW_CFG_SYSFS)
+	if (running_on_qemu) {
+		struct resource res[3] = {0,};
+		unsigned int base;
+
+		base = ((unsigned long long) PAGE0->pad0[2] << 32)
+			| PAGE0->pad0[3]; /* SeaBIOS stored it here */
+
+		res[0].name = "fw_cfg";
+		res[0].start = base;
+		res[0].end = base + 8 - 1;
+		res[0].flags = IORESOURCE_MEM;
+
+		res[1].name = "ctrl";
+		res[1].start = 0;
+		res[1].flags = IORESOURCE_REG;
+
+		res[2].name = "data";
+		res[2].start = 4;
+		res[2].flags = IORESOURCE_REG;
+
+		if (base) {
+			pr_info("Found qemu fw_cfg interface at %#08x\n", base);
+			platform_device_register_simple("fw_cfg",
+				PLATFORM_DEVID_NONE, res, 3);
+		}
+	}
+#endif
 }