On 12/01/2016 05:27 AM, Andre Przywara wrote:
> Hi,
>
> On 01/12/16 05:16, Wei Huang wrote:
>> From: Christopher Covington <cov@xxxxxxxxxxxxxx>
>>
>> Ensure that reads of the PMCCNTR_EL0 are monotonically increasing,
>> even for the smallest delta of two subsequent reads.
>>
>> Signed-off-by: Christopher Covington <cov@xxxxxxxxxxxxxx>
>> Signed-off-by: Wei Huang <wei@xxxxxxxxxx>
>> Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
>> ---
>> arm/pmu.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 94 insertions(+)
>>
>> diff --git a/arm/pmu.c b/arm/pmu.c
>> index 1fe2b1a..3566a27 100644
>> --- a/arm/pmu.c
>> +++ b/arm/pmu.c
>> @@ -16,6 +16,9 @@
>> #include "asm/barrier.h"
>> #include "asm/processor.h"
>>
>> +#define PMU_PMCR_E (1 << 0)
>> +#define PMU_PMCR_C (1 << 2)
>> +#define PMU_PMCR_LC (1 << 6)
>> #define PMU_PMCR_N_SHIFT 11
>> #define PMU_PMCR_N_MASK 0x1f
>> #define PMU_PMCR_ID_SHIFT 16
>> @@ -23,10 +26,57 @@
>> #define PMU_PMCR_IMP_SHIFT 24
>> #define PMU_PMCR_IMP_MASK 0xff
>>
>> +#define ID_DFR0_PERFMON_SHIFT 24
>> +#define ID_DFR0_PERFMON_MASK 0xf
>> +
>> +#define PMU_CYCLE_IDX 31
>> +
>> +#define NR_SAMPLES 10
>> +
>> +static unsigned int pmu_version;
>> #if defined(__arm__)
>> DEFINE_GET_SYSREG32(pmcr, 0, c9, c12, 0)
>> +DEFINE_SET_SYSREG32(pmcr, 0, c9, c12, 0)
>> +DEFINE_GET_SYSREG32(id_dfr0, 0, c0, c1, 2)
>> +DEFINE_SET_SYSREG32(pmselr, 0, c9, c12, 5)
>> +DEFINE_SET_SYSREG32(pmxevtyper, 0, c9, c13, 1)
>> +DEFINE_GET_SYSREG32(pmccntr32, 0, c9, c13, 0)
>> +DEFINE_SET_SYSREG32(pmccntr32, 0, c9, c13, 0)
>> +DEFINE_GET_SYSREG64(pmccntr64, 0, c9)
>> +DEFINE_SET_SYSREG64(pmccntr64, 0, c9)
>> +DEFINE_SET_SYSREG32(pmcntenset, 0, c9, c12, 1)
>> +
>> +static inline uint64_t get_pmccntr(void)
>> +{
>> + if (pmu_version == 0x3)
>> + return get_pmccntr64();
>> + else
>> + return get_pmccntr32();
>> +}
>> +
>> +static inline void set_pmccntr(uint64_t value)
>> +{
>> + if (pmu_version == 0x3)
>> + set_pmccntr64(value);
>> + else
>> + set_pmccntr32(value & 0xffffffff);
>> +}
>> +
>> +/* PMCCFILTR is an obsolete name for PMXEVTYPER31 in ARMv7 */
>> +static inline void set_pmccfiltr(uint32_t value)
>> +{
>> + set_pmselr(PMU_CYCLE_IDX);
>> + set_pmxevtyper(value);
>> + isb();
>> +}
>> #elif defined(__aarch64__)
>> DEFINE_GET_SYSREG32(pmcr, el0)
>> +DEFINE_SET_SYSREG32(pmcr, el0)
>> +DEFINE_GET_SYSREG32(id_dfr0, el1)
>> +DEFINE_GET_SYSREG64(pmccntr, el0);
>> +DEFINE_SET_SYSREG64(pmccntr, el0);
>> +DEFINE_SET_SYSREG32(pmcntenset, el0);
>> +DEFINE_SET_SYSREG32(pmccfiltr, el0);
>> #endif
>>
>> /*
>> @@ -52,11 +102,55 @@ static bool check_pmcr(void)
>> return ((pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK) != 0;
>> }
>>
>> +/*
>> + * Ensure that the cycle counter progresses between back-to-back reads.
>> + */
>> +static bool check_cycles_increase(void)
>> +{
>> + bool success = true;
>> +
>> + /* init before event access, this test only cares about cycle count */
>> + set_pmcntenset(1 << PMU_CYCLE_IDX);
>> + set_pmccfiltr(0); /* count cycles in EL0, EL1, but not EL2 */
>> + set_pmccntr(0);
>
> Why do we need this? Shouldn't PMU_PMCR_C below take care of that?
PMU_PMCR_C does reset cycle counter, I can remove this one.
>
>> +
>> + set_pmcr(get_pmcr() | PMU_PMCR_LC | PMU_PMCR_C | PMU_PMCR_E);
>> +
>> + for (int i = 0; i < NR_SAMPLES; i++) {
>> + uint64_t a, b;
>> +
>> + a = get_pmccntr();
>> + b = get_pmccntr();
>> +
>> + if (a >= b) {
>> + printf("Read %"PRId64" then %"PRId64".\n", a, b);
>> + success = false;
>> + break;
>> + }
>> + }
>> +
>> + set_pmcr(get_pmcr() & ~PMU_PMCR_E);
>> +
>> + return success;
>> +}
>> +
>> +void pmu_init(void)
>
> Mmh, this function doesn't really initialize anything, does it?
> Should it be named pmu_available() or pmu_version() or the like?
>
This function used to contain cycle counter configuration code. It sets
up PMCCNFILTR, PMCNTENSET, etc. Since then, the configuration code has
been moved to sub-unit tests. We can change its name to something like
pmu_probe().
> And should we bail out early here (or rather at the caller) if this
> register reports that no PMU is available? For instance by making it
> return a boolean?
This could do.
>
>> +{
>> + uint32_t dfr0;
>> +
>> + /* probe pmu version */
>> + dfr0 = get_id_dfr0();
>> + pmu_version = (dfr0 >> ID_DFR0_PERFMON_SHIFT) & ID_DFR0_PERFMON_MASK;
>> + report_info("PMU version: %d", pmu_version);
>> +}
>> +
>> int main(void)
>> {
>> report_prefix_push("pmu");
>>
>> + pmu_init();
>> report("Control register", check_pmcr());
>> + report("Monotonically increasing cycle count", check_cycles_increase());
>
> I wonder if we should skip this test if check_pmcr() has returned false
> before? We let it return a boolean, so it seems quite natural to use
> this information here.
> This would avoid a lot of false FAILs due to the PMU not being available
> (because QEMU is too old, for instance).
>
> Cheers,
> Andre.
>
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