Re: [PATCH 17/42] PCI: aardvark: Fix support for MSI interrupts

From: Pali Rohár
Date: Fri May 07 2021 - 10:44:26 EST


On Friday 07 May 2021 11:16:58 Marc Zyngier wrote:
> On Thu, 06 May 2021 16:31:28 +0100,
> Pali Rohár <pali@xxxxxxxxxx> wrote:
> >
> > MSI domain callback .alloc (implemented by advk_msi_irq_domain_alloc()
> > function) should return zero on success. Returning non-zero value indicates
> > failure. Fix return value of this function as in many cases it now returns
> > failure while allocating IRQs.
> >
> > Aardvark hardware supports Multi-MSI and MSI_FLAG_MULTI_PCI_MSI is already
> > set. But when allocating MSI interrupt numbers for Multi-MSI, they need to
> > be properly aligned, otherwise endpoint devices send MSI interrupt with
> > incorrect numbers. Fix this issue by using function bitmap_find_free_region()
> > instead of bitmap_find_next_zero_area().
> >
> > To ensure that aligned MSI interrupt numbers are used by endpoint devices,
> > we cannot use Linux virtual irq numbers (as they are random and not
> > properly aligned). So use hwirq numbers allocated by the function
> > bitmap_find_free_region(), which are aligned. This needs an update in
> > advk_msi_irq_compose_msi_msg() and advk_pcie_handle_msi() functions to do
> > proper mapping between Linux virtual irq numbers and hwirq MSI inner domain
> > numbers.
> >
> > Also the whole 16-bit MSI number is stored in the PCIE_MSI_PAYLOAD_REG
> > register, not only lower 8 bits. Fix reading content of this register.
> >
> > This change fixes receiving MSI interrupts on Armada 3720 boards and allows
> > using NVMe disks which use Multi-MSI feature with 3 interrupts.
> >
> > Without this change, NVMe disks just freeze booting Linux on Armada 3720
> > boards as linux nvme-core.c driver is waiting 60s for an interrupt.
> >
> > Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
> > Reviewed-by: Marek Behún <kabel@xxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx # f21a8b1b6837 ("PCI: aardvark: Move to MSI handling using generic MSI support")
> > ---
> > drivers/pci/controller/pci-aardvark.c | 32 ++++++++++++++++-----------
> > 1 file changed, 19 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > index 366d7480bc1b..498810c00b6d 100644
> > --- a/drivers/pci/controller/pci-aardvark.c
> > +++ b/drivers/pci/controller/pci-aardvark.c
> > @@ -118,6 +118,7 @@
> > #define PCIE_MSI_STATUS_REG (CONTROL_BASE_ADDR + 0x58)
> > #define PCIE_MSI_MASK_REG (CONTROL_BASE_ADDR + 0x5C)
> > #define PCIE_MSI_PAYLOAD_REG (CONTROL_BASE_ADDR + 0x9C)
> > +#define PCIE_MSI_DATA_MASK GENMASK(15, 0)
>
> See my comment below about this addition.
>
> > /* LMI registers base address and register offsets */
> > #define LMI_BASE_ADDR 0x6000
> > @@ -861,7 +862,7 @@ static void advk_msi_irq_compose_msi_msg(struct irq_data *data,
> >
> > msg->address_lo = lower_32_bits(msi_msg);
> > msg->address_hi = upper_32_bits(msi_msg);
> > - msg->data = data->irq;
> > + msg->data = data->hwirq;
> > }
> >
> > static int advk_msi_set_affinity(struct irq_data *irq_data,
> > @@ -878,15 +879,11 @@ static int advk_msi_irq_domain_alloc(struct irq_domain *domain,
> > int hwirq, i;
> >
> > mutex_lock(&pcie->msi_used_lock);
> > - hwirq = bitmap_find_next_zero_area(pcie->msi_used, MSI_IRQ_NUM,
> > - 0, nr_irqs, 0);
> > - if (hwirq >= MSI_IRQ_NUM) {
> > - mutex_unlock(&pcie->msi_used_lock);
> > - return -ENOSPC;
> > - }
> > -
> > - bitmap_set(pcie->msi_used, hwirq, nr_irqs);
> > + hwirq = bitmap_find_free_region(pcie->msi_used, MSI_IRQ_NUM,
> > + order_base_2(nr_irqs));
> > mutex_unlock(&pcie->msi_used_lock);
> > + if (hwirq < 0)
> > + return -ENOSPC;
> >
> > for (i = 0; i < nr_irqs; i++)
> > irq_domain_set_info(domain, virq + i, hwirq + i,
> > @@ -894,7 +891,7 @@ static int advk_msi_irq_domain_alloc(struct irq_domain *domain,
> > domain->host_data, handle_simple_irq,
> > NULL, NULL);
> >
> > - return hwirq;
> > + return 0;
> > }
> >
> > static void advk_msi_irq_domain_free(struct irq_domain *domain,
> > @@ -904,7 +901,7 @@ static void advk_msi_irq_domain_free(struct irq_domain *domain,
> > struct advk_pcie *pcie = domain->host_data;
> >
> > mutex_lock(&pcie->msi_used_lock);
> > - bitmap_clear(pcie->msi_used, d->hwirq, nr_irqs);
> > + bitmap_release_region(pcie->msi_used, d->hwirq, order_base_2(nr_irqs));
> > mutex_unlock(&pcie->msi_used_lock);
> > }
> >
> > @@ -1048,6 +1045,7 @@ static void advk_pcie_handle_msi(struct advk_pcie *pcie)
> > {
> > u32 msi_val, msi_mask, msi_status, msi_idx;
> > u16 msi_data;
> > + int virq;
> >
> > msi_mask = advk_readl(pcie, PCIE_MSI_MASK_REG);
> > msi_val = advk_readl(pcie, PCIE_MSI_STATUS_REG);
> > @@ -1057,9 +1055,17 @@ static void advk_pcie_handle_msi(struct advk_pcie *pcie)
> > if (!(BIT(msi_idx) & msi_status))
> > continue;
> >
> > + /*
> > + * msi_idx contains bits [4:0] of the msi_data and msi_data
> > + * contains 16bit MSI interrupt number from MSI inner domain
> > + */
> > advk_writel(pcie, BIT(msi_idx), PCIE_MSI_STATUS_REG);
> > - msi_data = advk_readl(pcie, PCIE_MSI_PAYLOAD_REG) & 0xFF;
> > - generic_handle_irq(msi_data);
> > + msi_data = advk_readl(pcie, PCIE_MSI_PAYLOAD_REG) & PCIE_MSI_DATA_MASK;
>
> Can this be moved to a separate patch? It seems like this patch should
> only focus on correctly dealing with the irq/hwirq issues.

Well, hwirq is read from PCIE_MSI_PAYLOAD_REG register and it is 16-bit.
That is why I included this change in this patch, to fix also reading
IRQ number, not only setting IRQ number.

> > + virq = irq_find_mapping(pcie->msi_inner_domain, msi_data);
> > + if (virq)
> > + generic_handle_irq(virq);
> > + else
> > + dev_err(&pcie->pdev->dev, "unexpected MSI 0x%04hx\n", msi_data);
>
> Same concern about the unmitigated screaming.
>
> Thanks,
>
> M.
>
> --
> Without deviation from the norm, progress is not possible.