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From:   Joakim Zhang <qiangqing.zhang@nxp.com>
To:     "peterz@infradead.org" <peterz@infradead.org>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "acme@kernel.org" <acme@kernel.org>,
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CC:     Frank Li <frank.li@nxp.com>, dl-linux-imx <linux-imx@nxp.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Joakim Zhang <qiangqing.zhang@nxp.com>
Subject: [PATCH] perf tool: arch: arm64: change the way for get_cpuid_str()
 function
Thread-Topic: [PATCH] perf tool: arch: arm64: change the way for
 get_cpuid_str() function
Thread-Index: AQHVPTEJbljaEfwA1kmeHm0+nYaIVA==
Date:   Thu, 18 Jul 2019 06:21:30 +0000
Message-ID: <20190718061853.10403-1-qiangqing.zhang@nxp.com>
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Now the get_cpuid__str function returns the MIDR string of the first
online cpu from the range of cpus asscociated with the PMU CORE device.

It can work when pass a perf_pmu entity to get_cpuid_str. However, it
will pass NULL via perf_pmu__find_map from metricgroup.c if we want to add
metric group for arm64. When pass NULL to get_cpuid_str, it can't return
the MIDR string.

There are three methods from userspace getting MIDR string for arm64:
1. parse sysfs(/sys/devices/system/cpu/cpu?/regs/identification/midr_el1)
2. parse procfs(/proc/cpuinfo)
3. read the hwcaps(MIDR register) with getauxval(AT_HWCAP)

Perfer to select #3 as it is more simple and direct.

Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
---
 tools/perf/arch/arm64/util/header.c | 68 +++++++++++------------------
 1 file changed, 25 insertions(+), 43 deletions(-)

diff --git a/tools/perf/arch/arm64/util/header.c b/tools/perf/arch/arm64/ut=
il/header.c
index 534cd2507d83..f58f08af0be8 100644
--- a/tools/perf/arch/arm64/util/header.c
+++ b/tools/perf/arch/arm64/util/header.c
@@ -2,64 +2,46 @@
 #include <stdlib.h>
 #include <api/fs/fs.h>
 #include "header.h"
+#include <asm/hwcap.h>
+#include <sys/auxv.h>
=20
-#define MIDR "/regs/identification/midr_el1"
 #define MIDR_SIZE 19
 #define MIDR_REVISION_MASK      0xf
 #define MIDR_VARIANT_SHIFT      20
 #define MIDR_VARIANT_MASK       (0xf << MIDR_VARIANT_SHIFT)
=20
-char *get_cpuid_str(struct perf_pmu *pmu)
+#define get_cpuid(id) ({					\
+		unsigned long __val;				\
+		asm("mrs %0, "#id : "=3Dr" (__val));		\
+		__val;						\
+	})
+
+char *get_cpuid_str(struct perf_pmu *pmu __maybe_unused)
 {
 	char *buf =3D NULL;
-	char path[PATH_MAX];
-	const char *sysfs =3D sysfs__mountpoint();
-	int cpu;
-	u64 midr =3D 0;
-	struct cpu_map *cpus;
-	FILE *file;
+	unsigned long midr =3D 0;
=20
-	if (!sysfs || !pmu || !pmu->cpus)
+	if (!(getauxval(AT_HWCAP) & HWCAP_CPUID)) {
+		fputs("CPUID registers unavailable\n", stderr);
 		return NULL;
+	}
=20
-	buf =3D malloc(MIDR_SIZE);
-	if (!buf)
+	midr =3D get_cpuid(MIDR_EL1);
+	if (!midr) {
+		fputs("Failed to get cpuid string\n", stderr);
 		return NULL;
+	}
=20
-	/* read midr from list of cpus mapped to this pmu */
-	cpus =3D cpu_map__get(pmu->cpus);
-	for (cpu =3D 0; cpu < cpus->nr; cpu++) {
-		scnprintf(path, PATH_MAX, "%s/devices/system/cpu/cpu%d"MIDR,
-				sysfs, cpus->map[cpu]);
-
-		file =3D fopen(path, "r");
-		if (!file) {
-			pr_debug("fopen failed for file %s\n", path);
-			continue;
-		}
-
-		if (!fgets(buf, MIDR_SIZE, file)) {
-			fclose(file);
-			continue;
-		}
-		fclose(file);
+	/* Ignore/clear Variant[23:20] and
+	 * Revision[3:0] of MIDR
+	 */
+	midr &=3D (~(MIDR_VARIANT_MASK | MIDR_REVISION_MASK));
=20
-		/* Ignore/clear Variant[23:20] and
-		 * Revision[3:0] of MIDR
-		 */
-		midr =3D strtoul(buf, NULL, 16);
-		midr &=3D (~(MIDR_VARIANT_MASK | MIDR_REVISION_MASK));
-		scnprintf(buf, MIDR_SIZE, "0x%016lx", midr);
-		/* got midr break loop */
-		break;
-	}
+	buf =3D malloc(MIDR_SIZE);
+	if (!buf)
+		return NULL;
=20
-	if (!midr) {
-		pr_err("failed to get cpuid string for PMU %s\n", pmu->name);
-		free(buf);
-		buf =3D NULL;
-	}
+	scnprintf(buf, MIDR_SIZE, "0x%016lx", midr);
=20
-	cpu_map__put(cpus);
 	return buf;
 }
--=20
2.17.1