Re: [PATCH 2/2] iommu/riscv: support HPM and interrupt handling

Zong Li
2025-01-17T02:33:25Z

On Wed, Jan 15, 2025 at 5:44 PM Andrew Jones <ajones@ventanamicro.com> wrote:
>
> On Wed, Jan 15, 2025 at 11:03:06AM +0800, Zong Li wrote:
> > Initialize the PMU and uninitialize it when driver is removed.
> > Interrupt handling is also implemented, and the handler needs
> > to be a primary handler instead of a threaded function because
> > pt_regs is empty when threading the IRQ. However, pt_regs is
> > required by perf_event_overflow.
> >
> > Signed-off-by: Zong Li <zong.li@sifive.com>
> > Tested-by: Xu Lu <luxu.kernel@bytedance.com>
> > ---
> > drivers/iommu/riscv/iommu.c | 65 +++++++++++++++++++++++++++++++++++++
> > 1 file changed, 65 insertions(+)
> >
> > diff --git a/drivers/iommu/riscv/iommu.c b/drivers/iommu/riscv/iommu.c
> > index 8a05def774bd..20ae90471484 100644
> > --- a/drivers/iommu/riscv/iommu.c
> > +++ b/drivers/iommu/riscv/iommu.c
> > @@ -552,6 +552,62 @@ static irqreturn_t riscv_iommu_fltq_process(int irq, void *data)
> > return IRQ_HANDLED;
> > }
> >
> > +/*
> > + * IOMMU Hardware performance monitor
> > + */
> > +
> > +/* HPM interrupt primary handler */
> > +static irqreturn_t riscv_iommu_hpm_irq_handler(int irq, void *dev_id)
> > +{
> > + struct riscv_iommu_device *iommu = (struct riscv_iommu_device *)dev_id;
> > +
> > + /* Clear performance monitoring interrupt pending */
> > + riscv_iommu_writel(iommu, RISCV_IOMMU_REG_IPSR, RISCV_IOMMU_IPSR_PMIP);
> > +
> > + /* Process pmu irq */
> > + riscv_iommu_pmu_handle_irq(&iommu->pmu);
> > +
> > + return IRQ_HANDLED;
> > +}
> > +
> > +/* HPM initialization */
> > +static int riscv_iommu_hpm_enable(struct riscv_iommu_device *iommu)
> > +{
> > + int rc;
> > +
> > + if (!(iommu->caps & RISCV_IOMMU_CAPABILITIES_HPM))
> > + return 0;
> > +
> > + /*
> > + * pt_regs is empty when threading the IRQ, but pt_regs is necessary
> > + * by perf_event_overflow. Use primary handler instead of thread
> > + * function for PM IRQ.
> > + *
> > + * Set the IRQF_ONESHOT flag because this IRQ might be shared with
> > + * other threaded IRQs by other queues.
> > + */
> > + rc = devm_request_irq(iommu->dev,
> > + iommu->irqs[riscv_iommu_queue_vec(iommu, RISCV_IOMMU_IPSR_PMIP)],
> > + riscv_iommu_hpm_irq_handler, IRQF_ONESHOT | IRQF_SHARED, NULL, iommu);
> > + if (rc)
> > + return rc;
> > +
> > + return riscv_iommu_pmu_init(&iommu->pmu, iommu->reg, dev_name(iommu->dev));
> > +}
> > +
> > +/* HPM uninitialization */
> > +static void riscv_iommu_hpm_disable(struct riscv_iommu_device *iommu)
> > +{
> > + if (!(iommu->caps & RISCV_IOMMU_CAPABILITIES_HPM))
> > + return;
> > +
> > + devm_free_irq(iommu->dev,
> > + iommu->irqs[riscv_iommu_queue_vec(iommu, RISCV_IOMMU_IPSR_PMIP)],
> > + iommu);
> > +
> > + riscv_iommu_pmu_uninit(&iommu->pmu);
> > +}
> > +
> > /* Lookup and initialize device context info structure. */
> > static struct riscv_iommu_dc *riscv_iommu_get_dc(struct riscv_iommu_device *iommu,
> > unsigned int devid)
> > @@ -1596,6 +1652,9 @@ void riscv_iommu_remove(struct riscv_iommu_device *iommu)
> > riscv_iommu_iodir_set_mode(iommu, RISCV_IOMMU_DDTP_IOMMU_MODE_OFF);
> > riscv_iommu_queue_disable(&iommu->cmdq);
> > riscv_iommu_queue_disable(&iommu->fltq);
> > +
> > + if (iommu->caps & RISCV_IOMMU_CAPABILITIES_HPM)
> > + riscv_iommu_pmu_uninit(&iommu->pmu);
>
> This should be
>
> riscv_iommu_hpm_disable(iommu);
>
> as the cover letter said it would be.

Yes, I guess I messed that up. Thanks

>
> > }
> >
> > int riscv_iommu_init(struct riscv_iommu_device *iommu)
> > @@ -1635,6 +1694,10 @@ int riscv_iommu_init(struct riscv_iommu_device *iommu)
> > if (rc)
> > goto err_queue_disable;
> >
> > + rc = riscv_iommu_hpm_enable(iommu);
> > + if (rc)
> > + goto err_hpm_disable;
>
> This should be
>
> goto err_iodir_off;
>
> And the next goto (under sysfs add) should be
>
> goto err_hpm_disable;
>

Yes, thanks for catching that.

> > +
> > rc = iommu_device_sysfs_add(&iommu->iommu, NULL, NULL, "riscv-iommu@%s",
> > dev_name(iommu->dev));
> > if (rc) {
> > @@ -1653,6 +1716,8 @@ int riscv_iommu_init(struct riscv_iommu_device *iommu)
> > err_remove_sysfs:
> > iommu_device_sysfs_remove(&iommu->iommu);
> > err_iodir_off:
> > + riscv_iommu_hpm_disable(iommu);
> > +err_hpm_disable:
> > riscv_iommu_iodir_set_mode(iommu, RISCV_IOMMU_DDTP_IOMMU_MODE_OFF);
> > err_queue_disable:
> > riscv_iommu_queue_disable(&iommu->fltq);
>
> This should be
>
> err_remove_sysfs:
> ...
> err_hpm_disable:
> ...
> err_iodir_off:
> ...
> err_queue_disable:
> ...
>

Let me try to fix them in the next version if necessary. As Robin
mentioned, we might not need the HPM cleaner and can simply enable HPM
at the end. Thanks you for the review and catching these.

>
> Thanks,
> drew