Re: [PATCH v4 1/1] RISC-V: Create unique identification for SoC PMU

[Nikita Shubin]

On Mon, 20 Jun 2022 17:30:58 +0530
Anup Patel <apatel@xxxxxxxxxxxxxxxx> wrote:

> On Sun, Jun 19, 2022 at 4:41 PM Nikita Shubin
> <nikita.shubin@xxxxxxxxxxx> wrote:
> >
> > From: Nikita Shubin <n.shubin@xxxxxxxxx>
> >
> > Provide RISC-V SBI PMU id to distinguish different cores or SoCs via
> > "devices/platform/riscv-pmu/id" sysfs entry.
> >
> > The identification is generated as string of marchid, mimpid,
> > mvendorid in hex format separated by coma - "0x70032,0x70032,0x0".
> >
> > The CSRs are detailed in the RISC-V privileged spec [1].
> > [1] https://github.com/riscv/riscv-isa-manual
> >
> > Inspired-by: João Mário Domingos <joao.mario@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Nikita Shubin <n.shubin@xxxxxxxxx>  
> 
> The mvendorid, marchid, and mimpid can be useful to apps other than
> perf tool.
> 
> I have tried to extend /proc/cpuinfo with this information which can
> be parsed by perf tool:
> https://lore.kernel.org/all/20220620115549.1529597-1-apatel@xxxxxxxxxxxxxxxx/

Atish, what do you think about this ?

RISC-V perf can rely on "/proc/cpuinfo", in some similar manner like
"tools/perf/arch/s390/util/header.c" does.

Can it create problems with pmu identification in case of hetergenous
harts ?

> 
> Regards,
> Anup
> 
> > ---
> > v3->v4:
> > - use string for pmuid
> > - rename pmu_sbi_id_show to id_show
> > - fix error print message in id_show
> > - fix DEVICE_ATTR to use octal permissions
> > ---
> >  arch/riscv/kernel/sbi.c        |  3 +++
> >  drivers/perf/riscv_pmu_sbi.c   | 41
> > ++++++++++++++++++++++++++++++++++ include/linux/perf/riscv_pmu.h |
> >  1 + 3 files changed, 45 insertions(+)
> >
> > diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> > index 775d3322b422..50dd9b6ecc9e 100644
> > --- a/arch/riscv/kernel/sbi.c
> > +++ b/arch/riscv/kernel/sbi.c
> > @@ -627,16 +627,19 @@ long sbi_get_mvendorid(void)
> >  {
> >         return __sbi_base_ecall(SBI_EXT_BASE_GET_MVENDORID);
> >  }
> > +EXPORT_SYMBOL(sbi_get_mvendorid);
> >
> >  long sbi_get_marchid(void)
> >  {
> >         return __sbi_base_ecall(SBI_EXT_BASE_GET_MARCHID);
> >  }
> > +EXPORT_SYMBOL(sbi_get_marchid);
> >
> >  long sbi_get_mimpid(void)
> >  {
> >         return __sbi_base_ecall(SBI_EXT_BASE_GET_MIMPID);
> >  }
> > +EXPORT_SYMBOL(sbi_get_mimpid);
> >
> >  static void sbi_send_cpumask_ipi(const struct cpumask *target)
> >  {
> > diff --git a/drivers/perf/riscv_pmu_sbi.c
> > b/drivers/perf/riscv_pmu_sbi.c index dca3537a8dcc..be812f855617
> > 100644 --- a/drivers/perf/riscv_pmu_sbi.c
> > +++ b/drivers/perf/riscv_pmu_sbi.c
> > @@ -693,6 +693,28 @@ static int pmu_sbi_setup_irqs(struct riscv_pmu
> > *pmu, struct platform_device *pde return 0;
> >  }
> >
> > +static ssize_t id_show(struct device *dev,
> > +                               struct device_attribute *attr, char
> > *buf) +{
> > +       int len;
> > +       struct riscv_pmu *pmu = container_of(dev_get_drvdata(dev),
> > struct riscv_pmu, pmu); +
> > +       len = sprintf(buf, "%s\n", pmu->pmuid);
> > +       if (len <= 0)
> > +               dev_err(dev, "invalid sprintf len: %d\n", len);
> > +
> > +       return len;
> > +}
> > +
> > +static DEVICE_ATTR(id, 0644, id_show, NULL);
> > +
> > +static struct attribute *pmu_sbi_attrs[] = {
> > +       &dev_attr_id.attr,
> > +       NULL
> > +};
> > +
> > +ATTRIBUTE_GROUPS(pmu_sbi);
> > +
> >  static int pmu_sbi_device_probe(struct platform_device *pdev)
> >  {
> >         struct riscv_pmu *pmu = NULL;
> > @@ -714,6 +736,14 @@ static int pmu_sbi_device_probe(struct
> > platform_device *pdev) if (pmu_sbi_get_ctrinfo(num_counters))
> >                 goto out_free;
> >
> > +       /* fill pmuid */
> > +       pmu->pmuid = kasprintf(GFP_KERNEL, "0x%lx,0x%lx,0x%lx",
> > +                              sbi_get_marchid(),
> > +                              sbi_get_mimpid(),
> > +                              sbi_get_mvendorid());
> > +       if (!pmu->pmuid)
> > +               goto out_free_pmuid;
> > +
> >         ret = pmu_sbi_setup_irqs(pmu, pdev);
> >         if (ret < 0) {
> >                 pr_info("Perf sampling/filtering is not supported
> > as sscof extension is not available\n"); @@ -739,8 +769,19 @@
> > static int pmu_sbi_device_probe(struct platform_device *pdev)
> > return ret; }
> >
> > +       ret = sysfs_create_group(&pdev->dev.kobj, &pmu_sbi_group);
> > +       if (ret) {
> > +               dev_err(&pdev->dev, "sysfs creation failed\n");
> > +               return ret;
> > +       }
> > +
> > +       pdev->dev.groups = pmu_sbi_groups;
> > +       dev_set_drvdata(&pdev->dev, pmu);
> > +
> >         return 0;
> >
> > +out_free_pmuid:
> > +       kfree(pmu->pmuid);
> >  out_free:
> >         kfree(pmu);
> >         return ret;
> > diff --git a/include/linux/perf/riscv_pmu.h
> > b/include/linux/perf/riscv_pmu.h index 46f9b6fe306e..cf3557b77fb8
> > 100644 --- a/include/linux/perf/riscv_pmu.h
> > +++ b/include/linux/perf/riscv_pmu.h
> > @@ -42,6 +42,7 @@ struct cpu_hw_events {
> >  struct riscv_pmu {
> >         struct pmu      pmu;
> >         char            *name;
> > +       char            *pmuid;
> >
> >         irqreturn_t     (*handle_irq)(int irq_num, void *dev);
> >
> > --
> > 2.35.1
> >