powerpc/watchpoint: Introduce function to get nr watchpoints dynamically

So far we had only one watchpoint, so we have hardcoded HBP_NUM to 1.
But Power10 is introducing 2nd DAWR and thus kernel should be able to
dynamically find actual number of watchpoints supported by hw it's
running on. Introduce function for the same. Also convert HBP_NUM macro
to HBP_NUM_MAX, which will now represent maximum number of watchpoints
supported by Powerpc.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Michael Neuling <mikey@neuling.org>
Link: https://lore.kernel.org/r/20200514111741.97993-4-ravi.bangoria@linux.ibm.com

4 files changed, 12 insertions, 3 deletions

diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index 40a4d3c6fd99..c67b94f3334c 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -614,7 +614,11 @@ enum {
 };
 #endif /* __powerpc64__ */
 
-#define HBP_NUM 1
+/*
+ * Maximum number of hw breakpoint supported on powerpc. Number of
+ * breakpoints supported by actual hw might be less than this.
+ */
+#define HBP_NUM_MAX	1
 
 #endif /* !__ASSEMBLY__ */
 
diff --git a/arch/powerpc/include/asm/hw_breakpoint.h b/arch/powerpc/include/asm/hw_breakpoint.h
index f2f8d8aa8e3b..518b41eef924 100644
--- a/arch/powerpc/include/asm/hw_breakpoint.h
+++ b/arch/powerpc/include/asm/hw_breakpoint.h
@@ -43,6 +43,11 @@ struct arch_hw_breakpoint {
 #define DABR_MAX_LEN	8
 #define DAWR_MAX_LEN	512
 
+static inline int nr_wp_slots(void)
+{
+	return HBP_NUM_MAX;
+}
+
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
 #include <linux/kdebug.h>
 #include <asm/reg.h>
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index 5ab202055d5a..f209c5703ee2 100644
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -180,7 +180,7 @@ struct thread_struct {
 	int		fpexc_mode;	/* floating-point exception mode */
 	unsigned int	align_ctl;	/* alignment handling control */
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
-	struct perf_event *ptrace_bps[HBP_NUM];
+	struct perf_event *ptrace_bps[HBP_NUM_MAX];
 	/*
 	 * Helps identify source of single-step exception and subsequent
 	 * hw-breakpoint enablement
diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index 423603c92c0f..01f07d91df70 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -39,7 +39,7 @@ static DEFINE_PER_CPU(struct perf_event *, bp_per_reg);
 int hw_breakpoint_slots(int type)
 {
 	if (type == TYPE_DATA)
-		return HBP_NUM;
+		return nr_wp_slots();
 	return 0;		/* no instruction breakpoints available */
 }