Messages in this thread |  | | Date | Wed, 23 Aug 2017 11:17:24 +0100 | From | Will Deacon <> | Subject | Re: [PATCH v5 2/4] perf tools arm64: Add support for get_cpuid_str function. |
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On Wed, Aug 16, 2017 at 12:40:46PM +0530, Ganapatrao Kulkarni wrote: > function get_cpuid_str returns MIDR string of the first online > cpu from the range of cpus associated with the pmu core device. > > Signed-off-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@cavium.com> > --- > tools/perf/arch/arm64/util/Build | 1 + > tools/perf/arch/arm64/util/header.c | 61 +++++++++++++++++++++++++++++++++++++ > 2 files changed, 62 insertions(+) > create mode 100644 tools/perf/arch/arm64/util/header.c > > diff --git a/tools/perf/arch/arm64/util/Build b/tools/perf/arch/arm64/util/Build > index cef6fb3..b1ab72d 100644 > --- a/tools/perf/arch/arm64/util/Build > +++ b/tools/perf/arch/arm64/util/Build > @@ -1,3 +1,4 @@ > +libperf-y += header.o > libperf-$(CONFIG_DWARF) += dwarf-regs.o > libperf-$(CONFIG_LOCAL_LIBUNWIND) += unwind-libunwind.o > > diff --git a/tools/perf/arch/arm64/util/header.c b/tools/perf/arch/arm64/util/header.c > new file mode 100644 > index 0000000..713ef17 > --- /dev/null > +++ b/tools/perf/arch/arm64/util/header.c > @@ -0,0 +1,61 @@ > +#include <stdio.h> > +#include <stdlib.h> > +#include <api/fs/fs.h> > +#include "header.h" > + > +#define MIDR "/regs/identification/midr_el1" > +#define MIDR_SIZE 128
Why is this so big?
> +char *get_cpuid_str(struct perf_pmu *pmu) > +{ > + char *buf = NULL; > + char *temp = NULL; > + char path[PATH_MAX]; > + const char *sysfs = sysfs__mountpoint(); > + int cpu; > + unsigned long long midr = 0; > + struct cpu_map *cpus; > + FILE *file; > + > + if (!sysfs || !pmu->cpus) > + return NULL; > + > + buf = malloc(MIDR_SIZE); > + if (!buf) > + return NULL; > + > + /* read midr from list of cpus mapped to this pmu */ > + cpus = cpu_map__get(pmu->cpus); > + for (cpu = 0; cpu < cpus->nr; cpu++) { > + scnprintf(path, PATH_MAX, "%s/devices/system/cpu/cpu%d"MIDR, > + sysfs, cpus->map[cpu]); > + > + file = fopen(path, "r"); > + if (!file) { > + pr_err("fopen failed for file %s\n", path);
pr_debug instead? It's not fatal if a CPU is hotplugged off and you can't read its midr.
> + continue; > + } > + > + temp = fgets(buf, MIDR_SIZE, file); > + if (!temp) > + continue;
Do you actually need a temporary variable for this?
> + fclose(file); > + > + /* Ignore/clear Variant[23:20] and > + * Revision[3:0] of MIDR > + */ > + midr = strtoll(buf, NULL, 16); > + midr &= (~(0xf << 20 | 0xf));
If midr really needs to be unsigned long long (u64 might be better), then you need to fix these immediates to have a ULL suffix.
Can you use the GENMASK_ULL macro to generate the MIDR mask, or is that not available here?
> + scnprintf(buf, MIDR_SIZE, "0x%016llx", midr); > + /* got midr break loop */ > + break; > + } > + > + if (!midr) { > + free(buf); > + buf = NULL;
If you want the pr_err, here would seem more appropriate because at this point we've actually failed.
Will
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