powerpc/watchpoint: Return available watchpoints dynamically

So far Book3S Powerpc supported only one watchpoint. Power10 is
introducing 2nd DAWR. Enable 2nd DAWR support for Power10.
Availability of 2nd DAWR will depend on CPU_FTR_DAWR1.
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200723090813.303838-10-ravi.bangoria@linux.ibm.com

arch/powerpc/include/asm/cputable.h

@@ -629,9 +629,10 @@ enum {
 
 /*
  * Maximum number of hw breakpoint supported on powerpc. Number of
- * breakpoints supported by actual hw might be less than this.
+ * breakpoints supported by actual hw might be less than this, which
+ * is decided at run time in nr_wp_slots().
  */
-#define HBP_NUM_MAX	1
+#define HBP_NUM_MAX	2
 
 #endif /* !__ASSEMBLY__ */
 

arch/powerpc/include/asm/hw_breakpoint.h

@@ -9,6 +9,8 @@
 #ifndef _PPC_BOOK3S_64_HW_BREAKPOINT_H
 #define _PPC_BOOK3S_64_HW_BREAKPOINT_H
 
+#include <asm/cpu_has_feature.h>
+
 #ifdef	__KERNEL__
 struct arch_hw_breakpoint {
 	unsigned long	address;
@@ -46,7 +48,7 @@ struct arch_hw_breakpoint {
 
 static inline int nr_wp_slots(void)
 {
-	return HBP_NUM_MAX;
+	return cpu_has_feature(CPU_FTR_DAWR1) ? 2 : 1;
 }
 
 #ifdef CONFIG_HAVE_HW_BREAKPOINT