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Message-ID: <0d7a984e-5814-a986-cd48-ef0651079e32@arm.com>
Date: Thu, 18 Oct 2018 12:43:59 +0100
From: Robin Murphy <robin.murphy@....com>
To: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
lorenzo.pieralisi@....com, jean-philippe.brucker@....com
Cc: will.deacon@....com, mark.rutland@....com, guohanjun@...wei.com,
john.garry@...wei.com, pabba@...eaurora.org,
vkilari@...eaurora.org, rruigrok@...eaurora.org,
linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linuxarm@...wei.com,
neil.m.leeder@...il.com
Subject: Re: [PATCH v4 4/4] perf/smmuv3_pmu: Enable HiSilicon Erratum
162001800 quirk
On 16/10/18 13:49, Shameer Kolothum wrote:
> HiSilicon erratum 162001800 describes the limitation of
> SMMUv3 PMCG implementation on HiSilicon Hip08 platforms.
>
> On these platforms, the PMCG event counter registers
> (SMMU_PMCG_EVCNTRn) are read only and as a result it is
> not possible to set the initial counter period value on
> event monitor start.
How the... oh well, never mind :(
> To work around this, the current value of the counter is
> read and is used for delta calculations. This increases
> the possibility of reporting incorrect values if counter
> overflow happens and counter passes the initial value.
>
> OEM information from ACPI header is used to identify the
> affected hardware platform.
I'm guessing they don't implement anything useful for SMMU_PMCG_ID_REGS?
(notwithstanding the known chicken-and-egg problem with how to interpret
those)
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
> ---
> drivers/perf/arm_smmuv3_pmu.c | 137 +++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 130 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
> index d927ef8..519545e 100644
> --- a/drivers/perf/arm_smmuv3_pmu.c
> +++ b/drivers/perf/arm_smmuv3_pmu.c
> @@ -96,6 +96,8 @@
>
> #define SMMU_PA_SHIFT 12
>
> +#define SMMU_PMU_OPT_EVCNTR_RDONLY (1 << 0)
> +
> static int cpuhp_state_num;
>
> struct smmu_pmu {
> @@ -111,10 +113,55 @@ struct smmu_pmu {
> struct device *dev;
> void __iomem *reg_base;
> void __iomem *reloc_base;
> + u32 options;
> u64 counter_present_mask;
> u64 counter_mask;
> };
>
> +struct erratum_acpi_oem_info {
> + char oem_id[ACPI_OEM_ID_SIZE + 1];
> + char oem_table_id[ACPI_OEM_TABLE_ID_SIZE + 1];
> + u32 oem_revision;
> +};
> +
> +static struct erratum_acpi_oem_info hisi_162001800_oem_info[] = {
> + /*
> + * Note that trailing spaces are required to properly match
> + * the OEM table information.
> + */
> + {
> + .oem_id = "HISI ",
> + .oem_table_id = "HIP08 ",
> + .oem_revision = 0,
> + },
> + { /* Sentinel indicating the end of the OEM array */ },
> +};
> +
> +enum smmu_pmu_erratum_match_type {
> + se_match_acpi_oem,
> +};
> +
> +void hisi_erratum_evcntr_rdonly(struct smmu_pmu *smmu_pmu)
> +{
> + smmu_pmu->options |= SMMU_PMU_OPT_EVCNTR_RDONLY;
> +}
> +
> +struct smmu_pmu_erratum_wa {
> + enum smmu_pmu_erratum_match_type match_type;
> + const void *id; /* Indicate the Erratum ID */
> + const char *desc_str;
> + void (*enable)(struct smmu_pmu *smmu_pmu);
> +};
> +
> +static const struct smmu_pmu_erratum_wa smmu_pmu_wa[] = {
> + {
> + .match_type = se_match_acpi_oem,
> + .id = hisi_162001800_oem_info,
> + .desc_str = "HiSilicon erratum 162001800",
> + .enable = hisi_erratum_evcntr_rdonly,
> + },
> +};
> +
There's an awful lot of raw ACPI internals splashed about here -
couldn't at least some of it be abstracted behind the IORT code? In
fact, can't IORT just set all this stuff up in advance like it does for
SMMUs?
> #define to_smmu_pmu(p) (container_of(p, struct smmu_pmu, pmu))
>
> #define SMMU_PMU_EVENT_ATTR_EXTRACTOR(_name, _config, _start, _end) \
> @@ -224,15 +271,20 @@ static void smmu_pmu_set_period(struct smmu_pmu *smmu_pmu,
> u32 idx = hwc->idx;
> u64 new;
>
> - /*
> - * We limit the max period to half the max counter value of the counter
> - * size, so that even in the case of extreme interrupt latency the
> - * counter will (hopefully) not wrap past its initial value.
> - */
> - new = smmu_pmu->counter_mask >> 1;
> + if (smmu_pmu->options & SMMU_PMU_OPT_EVCNTR_RDONLY) {
> + new = smmu_pmu_counter_get_value(smmu_pmu, idx);
Something's clearly missing, because if this happens to start at 0, the
current overflow handling code cannot possibly give the correct count.
Much as I hate the reset-to-half-period idiom for being impossible to
make sense of, it does make various aspects appear a lot simpler than
they really are. Wait, maybe that's yet another reason to hate it...
> + } else {
> + /*
> + * We limit the max period to half the max counter value
> + * of the counter size, so that even in the case of extreme
> + * interrupt latency the counter will (hopefully) not wrap
> + * past its initial value.
> + */
> + new = smmu_pmu->counter_mask >> 1;
> + smmu_pmu_counter_set_value(smmu_pmu, idx, new);
> + }
>
> local64_set(&hwc->prev_count, new);
> - smmu_pmu_counter_set_value(smmu_pmu, idx, new);
> }
>
> static void smmu_pmu_get_event_filter(struct perf_event *event, u32 *span,
> @@ -670,6 +722,69 @@ static void smmu_pmu_reset(struct smmu_pmu *smmu_pmu)
> smmu_pmu->reloc_base + SMMU_PMCG_OVSCLR0);
> }
>
> +typedef bool (*se_match_fn_t)(const struct smmu_pmu_erratum_wa *,
> + const void *);
> +
> +bool smmu_pmu_check_acpi_erratum(const struct smmu_pmu_erratum_wa *wa,
> + const void *arg)
> +{
> + static const struct erratum_acpi_oem_info empty_oem_info = {};
> + const struct erratum_acpi_oem_info *info = wa->id;
> + const struct acpi_table_header *hdr = arg;
> +
> + /* Iterate over the ACPI OEM info array, looking for a match */
> + while (memcmp(info, &empty_oem_info, sizeof(*info))) {
> + if (!memcmp(info->oem_id, hdr->oem_id, ACPI_OEM_ID_SIZE) &&
> + !memcmp(info->oem_table_id, hdr->oem_table_id, ACPI_OEM_TABLE_ID_SIZE) &&
> + info->oem_revision == hdr->oem_revision)
> + return true;
> +
> + info++;
> + }
> +
> + return false;
> +
> +}
> +
> +static void smmu_pmu_enable_errata(struct smmu_pmu *smmu_pmu,
> + enum smmu_pmu_erratum_match_type type,
> + se_match_fn_t match_fn,
> + void *arg)
> +{
> + const struct smmu_pmu_erratum_wa *wa = smmu_pmu_wa;
> +
> + for (; wa->desc_str; wa++) {
> + if (wa->match_type != type)
> + continue;
> +
> + if (match_fn(wa, arg)) {
> + if (wa->enable) {
> + wa->enable(smmu_pmu);
> + dev_info(smmu_pmu->dev,
> + "Enabling workaround for %s\n",
> + wa->desc_str);
> + }
Just how many kinds of broken are we expecting here? Is this lifted from
the arm64 cpufeature framework, because it seems like absolute overkill
for a simple PMU driver which in all reality is only ever going to
wiggle a few flags in some data structure.
Robin.
> + }
> + }
> +}
> +
> +static void smmu_pmu_check_workarounds(struct smmu_pmu *smmu_pmu,
> + enum smmu_pmu_erratum_match_type type,
> + void *arg)
> +{
> + se_match_fn_t match_fn = NULL;
> +
> + switch (type) {
> + case se_match_acpi_oem:
> + match_fn = smmu_pmu_check_acpi_erratum;
> + break;
> + default:
> + return;
> + }
> +
> + smmu_pmu_enable_errata(smmu_pmu, type, match_fn, arg);
> +}
> +
> static int smmu_pmu_probe(struct platform_device *pdev)
> {
> struct smmu_pmu *smmu_pmu;
> @@ -678,6 +793,7 @@ static int smmu_pmu_probe(struct platform_device *pdev)
> u64 ceid_64[2];
> int irq, err;
> char *name;
> + struct acpi_table_header *table;
> struct device *dev = &pdev->dev;
>
> smmu_pmu = devm_kzalloc(dev, sizeof(*smmu_pmu), GFP_KERNEL);
> @@ -749,6 +865,13 @@ static int smmu_pmu_probe(struct platform_device *pdev)
> return -EINVAL;
> }
>
> + if (ACPI_FAILURE(acpi_get_table(ACPI_SIG_IORT, 0, &table))) {
> + dev_err(dev, "IORT get failed, PMU @%pa\n", &res_0->start);
> + return -EINVAL;
> + }
> +
> + smmu_pmu_check_workarounds(smmu_pmu, se_match_acpi_oem, table);
> +
> /* Pick one CPU to be the preferred one to use */
> smmu_pmu->on_cpu = get_cpu();
> WARN_ON(irq_set_affinity(smmu_pmu->irq, cpumask_of(smmu_pmu->on_cpu)));
>
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