On Monday 07 June 2021 09:48:21 Ray Jui wrote:
> On 6/6/2021 5:30 AM, Sandor Bodo-Merle wrote:
> > The interrupt affinity scheme used by this driver is incompatible with
> > multi-MSI as it implies moving the doorbell address to that of another MSI
> > group. This isn't possible for multi-MSI, as all the MSIs must have the
> > same doorbell address. As such it is restricted to systems with a single
> > CPU.
> >
> > Fixes: fc54bae28818 ("PCI: iproc: Allow allocation of multiple MSIs")
> > Reported-by: Marc Zyngier <maz@xxxxxxxxxx>
> > Signed-off-by: Sandor Bodo-Merle <sbodomerle@xxxxxxxxx>
> > ---
> > drivers/pci/controller/pcie-iproc-msi.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/controller/pcie-iproc-msi.c b/drivers/pci/controller/pcie-iproc-msi.c
> > index 557d93dcb3bc..81b4effeb130 100644
> > --- a/drivers/pci/controller/pcie-iproc-msi.c
> > +++ b/drivers/pci/controller/pcie-iproc-msi.c
> > @@ -171,7 +171,7 @@ static struct irq_chip iproc_msi_irq_chip = {
> >
> > static struct msi_domain_info iproc_msi_domain_info = {
> > .flags = MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS |
> > - MSI_FLAG_MULTI_PCI_MSI | MSI_FLAG_PCI_MSIX,
> > + MSI_FLAG_PCI_MSIX,
> > .chip = &iproc_msi_irq_chip,
> > };
> >
> > @@ -250,6 +250,9 @@ static int iproc_msi_irq_domain_alloc(struct irq_domain *domain,
> > struct iproc_msi *msi = domain->host_data;
> > int hwirq, i;
> >
> > + if (msi->nr_cpus > 1 && nr_irqs > 1)
> > + return -EINVAL;
> > +
>
> This should never happen since the framework would have guarded against
> this. But I guess it does not hurt to have the check here.
Yes, this should not happen, but I suggested to add a comment or assert
or some other way to document this kind of constrain. Lot of times code
is copy+pasted to new drivers and because only this one driver has
.alloc function which is using nr_cpus for allocating msi bitmap, it
really makes sense to document this constrain also explicitly.
> > mutex_lock(&msi->bitmap_lock);
> >
> > /*
> > @@ -540,6 +543,9 @@ int iproc_msi_init(struct iproc_pcie *pcie, struct device_node *node)
> > mutex_init(&msi->bitmap_lock);
> > msi->nr_cpus = num_possible_cpus();
> >
> > + if (msi->nr_cpus == 1)
> > + iproc_msi_domain_info.flags |= MSI_FLAG_MULTI_PCI_MSI;
^^
Just a small note: there are two spaces instead of just one
Otherwise looks good to me:
Acked-by: Pali Rohár <pali@xxxxxxxxxx>
> > +
> > msi->nr_irqs = of_irq_count(node);
> > if (!msi->nr_irqs) {
> > dev_err(pcie->dev, "found no MSI GIC interrupt\n");
> >
>
> Looks fine to me. Thanks.
>
> Acked-by: Ray Jui <ray.jui@xxxxxxxxxxxx>
