watchdog: sp5100_tco.c: Check if firmware has set correct value in tcobase.

Stefano found SP5100 TCO watchdog driver using wrong address.

[    9.148536] SP5100 TCO timer: SP5100 TCO WatchDog Timer Driver v0.01
[    9.148628] DEBUG __ioremap_caller WARNING address=b8fe00 size=8 valid=1 reserved=1

and e820 said that range is RAM.

We should check if we can use that reading out. BIOS could just program wrong address there.
Reported-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Mike Waychison <mikew@google.com>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Cc: stable <stable@kernel.org>

drivers/watchdog/sp5100_tco.c

@@ -42,6 +42,7 @@
 #define PFX TCO_MODULE_NAME ": "
 
 /* internal variables */
+static u32 tcobase_phys;
 static void __iomem *tcobase;
 static unsigned int pm_iobase;
 static DEFINE_SPINLOCK(tco_lock);	/* Guards the hardware */
@@ -305,10 +306,18 @@ static unsigned char __devinit sp5100_tco_setupdevice(void)
 	/* Low three bits of BASE0 are reserved. */
 	val = val << 8 | (inb(SP5100_IO_PM_DATA_REG) & 0xf8);
 
+	if (!request_mem_region_exclusive(val, SP5100_WDT_MEM_MAP_SIZE,
+								"SP5100 TCO")) {
+		printk(KERN_ERR PFX "mmio address 0x%04x already in use\n",
+			val);
+		goto unreg_region;
+	}
+	tcobase_phys = val;
+
 	tcobase = ioremap(val, SP5100_WDT_MEM_MAP_SIZE);
 	if (tcobase == 0) {
 		printk(KERN_ERR PFX "failed to get tcobase address\n");
-		goto unreg_region;
+		goto unreg_mem_region;
 	}
 
 	/* Enable watchdog decode bit */
@@ -346,7 +355,8 @@ static unsigned char __devinit sp5100_tco_setupdevice(void)
 	/* Done */
 	return 1;
 
-	iounmap(tcobase);
+unreg_mem_region:
+	release_mem_region(tcobase_phys, SP5100_WDT_MEM_MAP_SIZE);
 unreg_region:
 	release_region(pm_iobase, SP5100_PM_IOPORTS_SIZE);
 exit:
@@ -401,6 +411,7 @@ static int __devinit sp5100_tco_init(struct platform_device *dev)
 
 exit:
 	iounmap(tcobase);
+	release_mem_region(tcobase_phys, SP5100_WDT_MEM_MAP_SIZE);
 	release_region(pm_iobase, SP5100_PM_IOPORTS_SIZE);
 	return ret;
 }
@@ -414,6 +425,7 @@ static void __devexit sp5100_tco_cleanup(void)
 	/* Deregister */
 	misc_deregister(&sp5100_tco_miscdev);
 	iounmap(tcobase);
+	release_mem_region(tcobase_phys, SP5100_WDT_MEM_MAP_SIZE);
 	release_region(pm_iobase, SP5100_PM_IOPORTS_SIZE);
 }