On Wed, Jul 29, 2015 at 5:15 PM, Marc Zyngier [off-list ref] wrote:

On 29/07/15 09:52, Ley Foon Tan wrote:

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On Wed, Jul 29, 2015 at 1:58 AM, Marc Zyngier [off-list ref] wrote:

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Hi Ley,

On 28/07/15 11:45, Ley Foon Tan wrote:

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This patch adds Altera PCIe MSI driver. This soft IP supports configurable
number of vectors, which is a dts parameter.

Can't you read this configuration from the HW?

No, we can't read from HW.

Ah, that's a shame. Specially on HW that is configurable by design.

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+
+                     irq = irq_find_mapping(msi->msi_domain->parent, offset);

This would tend to indicate that you don't really need to store the
msi_domain pointer, but the inner_domain pointer instead.

Will store the inner_domain pointer. But, I think we still need
msi_domain for irq_domain_remove.
Or do we have any way to retrieve msi_domain from inner_domain?

Do you have any case where you remove the domains, aside from the
obvious error cases?

Yes, if there is error in _probe().

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+
+static struct msi_domain_info altera_msi_domain_info = {
+     .flags  = (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS),

So you don't support MSIX? That's a bit weird.

Yes, this MSI IP doesn't support it.

This is not really a function of the MSI IP, but of the PCI device. In
your case, this is just a set of doorbells, so I hardly see what would
prevent MSI-X to be supported. Multi-MSI, I can see why.

Yes, you are right. Will add MSI_FLAG_PCI_MSIX flag here.

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+static int altera_msi_set_affinity(struct irq_data *irq_data,
+                              const struct cpumask *mask, bool force)
+{
+      return irq_set_affinity(irq_data->hwirq, mask);

There is no way this can be right. irq_data->hwirq can *never* be passed
as a Linux IRQ. This really should be the IRQ to the GIC.

Which raises another issue: as you only have a single interrupt to the
GIC, changing the affinity of a single MSI is going to affect all the
other MSIs as well. This doesn't seem like a desirable behaviour.

Do we must provide '.irq_set_affinity" callback to msi domain? I have
tried set it to NULL,
but kernel got the NULL pointer deference error from msi_domain_set_affinity().
Recently, I saw this new patch for pci-tegra.c from [1], it doesn't
set the ".irq_set_affinity".
Just wonder how it can work.

Do you have any recommendation way for this?

[1] https://git.kernel.org/cgit/linux/kernel/git/maz/arm-platforms.git/commit/drivers/pci/host?h=irq/gsi-irq-domain-v2&id=17c22fc4e60e6ad54c7e3b73868cbc057360fa63

Please realize that I *never* tested this patch (I don't think I ever
posted it officially, I just keep here for convenience), and I wouldn't
take it as a reference.

When it comes to msi_domain_set_affinity issue, this look more like an
oversight. I'll cook a patch for that.

Anyway, whichever way you want to do it, you need to fix this. You could
always return -EINVAL in the meantime,

Will add  -EINVAL for now.

Thanks for reviewing.

Regards
Ley Foon