x86/rtc, mrst: Don't register a platform RTC device for for Intel MID platforms

Intel MID x86 platforms have a memory mapped virtual RTC
instead.  No MID platform have the default ports (and
accessing them may do weird stuff).
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Cc: feng.tang@intel.com
Cc: Feng Tang <feng.tang@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/include/asm/mrst.h

@@ -31,11 +31,20 @@ enum mrst_cpu_type {
 };
 
 extern enum mrst_cpu_type __mrst_cpu_chip;
+
+#ifdef CONFIG_X86_INTEL_MID
+
 static inline enum mrst_cpu_type mrst_identify_cpu(void)
 {
 	return __mrst_cpu_chip;
 }
 
+#else /* !CONFIG_X86_INTEL_MID */
+
+#define mrst_identify_cpu()    (0)
+
+#endif /* !CONFIG_X86_INTEL_MID */
+
 enum mrst_timer_options {
 	MRST_TIMER_DEFAULT,
 	MRST_TIMER_APBT_ONLY,

arch/x86/kernel/rtc.c

@@ -12,6 +12,7 @@
 #include <asm/vsyscall.h>
 #include <asm/x86_init.h>
 #include <asm/time.h>
+#include <asm/mrst.h>
 
 #ifdef CONFIG_X86_32
 /*
@@ -242,6 +243,10 @@ static __init int add_rtc_cmos(void)
 	if (of_have_populated_dt())
 		return 0;
 
+	/* Intel MID platforms don't have ioport rtc */
+	if (mrst_identify_cpu())
+		return -ENODEV;
+
 	platform_device_register(&rtc_device);
 	dev_info(&rtc_device.dev,
 		 "registered platform RTC device (no PNP device found)\n");