linux-kernel - Re: [PATCH v2 03/10] riscv: Make legacy counter enum match the HW numbering

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Date:   Thu, 15 Jun 2023 09:16:51 +0200
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Andrew Jones <ajones@...tanamicro.com>,
        Alexandre Ghiti <alexghiti@...osinc.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atishp@...shpatra.org>,
        Anup Patel <anup@...infault.org>,
        Will Deacon <will@...nel.org>, Rob Herring <robh@...nel.org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 03/10] riscv: Make legacy counter enum match the HW
 numbering

On 31/05/2023 16:01, Andrew Jones wrote:
> On Fri, May 12, 2023 at 10:53:14AM +0200, Alexandre Ghiti wrote:
>> RISCV_PMU_LEGACY_INSTRET used to be set to 1 whereas the offset of this
>> hardware counter from CSR_CYCLE is actually 2: make this offset match the
>> real hw offset so that we can directly expose those values to userspace.
>>
>> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
>> ---
>>   drivers/perf/riscv_pmu_legacy.c | 7 +++++--
>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/perf/riscv_pmu_legacy.c b/drivers/perf/riscv_pmu_legacy.c
>> index ca9e20bfc7ac..0d8c9d8849ee 100644
>> --- a/drivers/perf/riscv_pmu_legacy.c
>> +++ b/drivers/perf/riscv_pmu_legacy.c
>> @@ -12,8 +12,11 @@
>>   #include <linux/perf/riscv_pmu.h>
>>   #include <linux/platform_device.h>
>>   
>> -#define RISCV_PMU_LEGACY_CYCLE		0
>> -#define RISCV_PMU_LEGACY_INSTRET	1
>> +enum {
>> +	RISCV_PMU_LEGACY_CYCLE,
>> +	RISCV_PMU_LEGACY_TIME,
>> +	RISCV_PMU_LEGACY_INSTRET
>> +};
> I guess this doesn't hurt, since these are just indices internal to this
> driver, but it's a bit odd to also have a RISCV_PMU_LEGACY_TIME, when
> the driver is only for cycle and instret, as its Kconfig help text says.


I understand and you're right, that's weird, so I'll change that with 
the following:

diff --git a/drivers/perf/riscv_pmu_legacy.c 
b/drivers/perf/riscv_pmu_legacy.c
index ca9e20bfc7ac..6a000abc28bb 100644
--- a/drivers/perf/riscv_pmu_legacy.c
+++ b/drivers/perf/riscv_pmu_legacy.c
@@ -13,7 +13,7 @@
  #include <linux/platform_device.h>

  #define RISCV_PMU_LEGACY_CYCLE         0
-#define RISCV_PMU_LEGACY_INSTRET       1
+#define RISCV_PMU_LEGACY_INSTRET       2

  static bool pmu_init_done;

Thanks!


> Thanks,
> drew
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv


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