powerpc/perf: Revert to original NO_SIPR logic

This is a revert and then some of commit 860aad71 "Add regs_no_sipr()".
This workaround was only needed on early chip versions.

As before NO_SIPR becomes a static flag of the PMU struct.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/perf/core-book3s.c

@@ -110,7 +110,7 @@ static inline void power_pmu_bhrb_read(struct cpu_hw_events *cpuhw) {}
 
 static bool regs_use_siar(struct pt_regs *regs)
 {
-	return !!(regs->result & 1);
+	return !!regs->result;
 }
 
 /*
@@ -181,11 +181,6 @@ static bool regs_sipr(struct pt_regs *regs)
 	return !!(regs->dsisr & sipr);
 }
 
-static bool regs_no_sipr(struct pt_regs *regs)
-{
-	return !!(regs->result & 2);
-}
-
 static inline u32 perf_flags_from_msr(struct pt_regs *regs)
 {
 	if (regs->msr & MSR_PR)
@@ -208,7 +203,7 @@ static inline u32 perf_get_misc_flags(struct pt_regs *regs)
 	 * SIAR which should give slightly more reliable
 	 * results
 	 */
-	if (regs_no_sipr(regs)) {
+	if (ppmu->flags & PPMU_NO_SIPR) {
 		unsigned long siar = mfspr(SPRN_SIAR);
 		if (siar >= PAGE_OFFSET)
 			return PERF_RECORD_MISC_KERNEL;
@@ -239,22 +234,9 @@ static inline void perf_read_regs(struct pt_regs *regs)
 	int use_siar;
 
 	regs->dsisr = mmcra;
-	regs->result = 0;
-
-	if (ppmu->flags & PPMU_NO_SIPR)
-		regs->result |= 2;
-
-	/*
-	 * On power8 if we're in random sampling mode, the SIER is updated.
-	 * If we're in continuous sampling mode, we don't have SIPR.
-	 */
-	if (ppmu->flags & PPMU_HAS_SIER) {
-		if (marked)
-			regs->dar = mfspr(SPRN_SIER);
-		else
-			regs->result |= 2;
-	}
 
+	if (ppmu->flags & PPMU_HAS_SIER)
+		regs->dar = mfspr(SPRN_SIER);
 
 	/*
 	 * If this isn't a PMU exception (eg a software event) the SIAR is
@@ -279,12 +261,12 @@ static inline void perf_read_regs(struct pt_regs *regs)
 		use_siar = 1;
 	else if ((ppmu->flags & PPMU_NO_CONT_SAMPLING))
 		use_siar = 0;
-	else if (!regs_no_sipr(regs) && regs_sipr(regs))
+	else if (!(ppmu->flags & PPMU_NO_SIPR) && regs_sipr(regs))
 		use_siar = 0;
 	else
 		use_siar = 1;
 
-	regs->result |= use_siar;
+	regs->result = use_siar;
 }
 
 /*