powerpc: Fix powerpc-specific watchdog build configuration

The powerpc kernel/watchdog.o should be built when HARDLOCKUP_DETECTOR
and HAVE_HARDLOCKUP_DETECTOR_ARCH are both selected. If only the former
is selected, then the generic perf watchdog has been selected.

To simplify this check, introduce a new Kconfig symbol PPC_WATCHDOG that
depends on both. This Kconfig option means the powerpc specific
watchdog is enabled.

Without this patch, Book3E will attempt to build the powerpc watchdog.

Fixes: 2104180a ("powerpc/64s: implement arch-specific hardlockup watchdog")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/Kconfig

@@ -85,6 +85,17 @@ config NMI_IPI
 	depends on SMP && (DEBUGGER || KEXEC_CORE || HARDLOCKUP_DETECTOR)
 	default y
 
+config PPC_WATCHDOG
+	bool
+	depends on HARDLOCKUP_DETECTOR
+	depends on HAVE_HARDLOCKUP_DETECTOR_ARCH
+	default y
+	help
+	  This is a placeholder when the powerpc hardlockup detector
+	  watchdog is selected (arch/powerpc/kernel/watchdog.c). It is
+	  seleted via the generic lockup detector menu which is why we
+	  have no standalone config option for it here.
+
 config STACKTRACE_SUPPORT
 	bool
 	default y

arch/powerpc/kernel/Makefile

@@ -38,7 +38,7 @@ obj-$(CONFIG_PPC64)		+= setup_64.o sys_ppc32.o \
 				   signal_64.o ptrace32.o \
 				   paca.o nvram_64.o firmware.o
 obj-$(CONFIG_VDSO32)		+= vdso32/
-obj-$(CONFIG_HARDLOCKUP_DETECTOR)	+= watchdog.o
+obj-$(CONFIG_PPC_WATCHDOG)	+= watchdog.o
 obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
 obj-$(CONFIG_PPC_BOOK3S_64)	+= cpu_setup_ppc970.o cpu_setup_pa6t.o
 obj-$(CONFIG_PPC_BOOK3S_64)	+= cpu_setup_power.o

arch/powerpc/kernel/exceptions-64s.S

@@ -1314,7 +1314,7 @@ EXC_REAL_NONE(0x1800, 0x100)
 EXC_VIRT_NONE(0x5800, 0x100)
 #endif
 
-#if defined(CONFIG_HARDLOCKUP_DETECTOR) && defined(CONFIG_HAVE_HARDLOCKUP_DETECTOR_ARCH)
+#ifdef CONFIG_PPC_WATCHDOG
 
 #define MASKED_DEC_HANDLER_LABEL 3f
 
@@ -1335,10 +1335,10 @@ EXC_COMMON_BEGIN(soft_nmi_common)
 			ADD_NVGPRS;ADD_RECONCILE)
 	b	ret_from_except
 
-#else
+#else /* CONFIG_PPC_WATCHDOG */
 #define MASKED_DEC_HANDLER_LABEL 2f /* normal return */
 #define MASKED_DEC_HANDLER(_H)
-#endif
+#endif /* CONFIG_PPC_WATCHDOG */
 
 /*
  * An interrupt came in while soft-disabled. We set paca->irq_happened, then: