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SubjectRe: [PATCH v4] PCI: xilinx-nwl: Fix Multi MSI data programming
On Wed, 12 Jun 2019 11:17:59 +0100,
Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com> wrote:
>
> The current Multi MSI data programming fails if multiple end points
> requesting MSI and multi MSI are connected with switch, i.e the current
> multi MSI data being given is not considering the number of vectors
> being requested in case of multi MSI.
> Ex: Two EP's connected via switch, EP1 requesting single MSI first,
> EP2 requesting Multi MSI of count four. The current code gives
> MSI data 0x0 to EP1 and 0x1 to EP2, but EP2 can modify lower two bits
> due to which EP2 also sends interrupt with MSI data 0x0 which results
> in always invoking virq of EP1 due to which EP2 MSI interrupt never
> gets handled.

I think there is a much simpler explanation for this: Multi-MSI
mandates that the base interrupt number is naturally aligned to its
size. Having switches in the middle is just a way to expose the issue,
but you could see it failing with a single end-point and two MSIs that
are assigned on an odd boundary.

>
> Fix Multi MSI data programming with required alignment by
> using number of vectors being requested.
>
> Fixes: ab597d35ef11 ("PCI: xilinx-nwl: Add support for Xilinx NWL PCIe
> Host Controller")
>
> Signed-off-by: Bharat Kumar Gogada <bharat.kumar.gogada@xilinx.com>
> ---
> V4:
> - Using a different bitmap registration API whcih serves single and multi
> MSI requests.
> ---
> drivers/pci/controller/pcie-xilinx-nwl.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pci/controller/pcie-xilinx-nwl.c b/drivers/pci/controller/pcie-xilinx-nwl.c
> index 81538d7..a9e07b8 100644
> --- a/drivers/pci/controller/pcie-xilinx-nwl.c
> +++ b/drivers/pci/controller/pcie-xilinx-nwl.c
> @@ -483,15 +483,13 @@ static int nwl_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
> int i;
>
> mutex_lock(&msi->lock);
> - bit = bitmap_find_next_zero_area(msi->bitmap, INT_PCI_MSI_NR, 0,
> - nr_irqs, 0);
> - if (bit >= INT_PCI_MSI_NR) {
> + bit = bitmap_find_free_region(msi->bitmap, INT_PCI_MSI_NR,
> + get_count_order(nr_irqs));
> + if (bit < 0) {
> mutex_unlock(&msi->lock);
> return -ENOSPC;
> }
>
> - bitmap_set(msi->bitmap, bit, nr_irqs);
> -
> for (i = 0; i < nr_irqs; i++) {
> irq_domain_set_info(domain, virq + i, bit + i, &nwl_irq_chip,
> domain->host_data, handle_simple_irq,
> @@ -509,7 +507,8 @@ static void nwl_irq_domain_free(struct irq_domain *domain, unsigned int virq,
> struct nwl_msi *msi = &pcie->msi;
>
> mutex_lock(&msi->lock);
> - bitmap_clear(msi->bitmap, data->hwirq, nr_irqs);
> + bitmap_release_region(msi->bitmap, data->hwirq,
> + get_count_order(nr_irqs));
> mutex_unlock(&msi->lock);
> }
>
> --
> 2.7.4
>

As for the body of the patch:

Suggested-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>

Thanks,

M.

--
Jazz is not dead, it just smells funny.

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