Messages in this thread Patch in this message | | | Date | Thu, 13 Jun 2019 10:22:33 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH+DISCUSSION] irqchip: armada-370-xp: Remove redundant ops assignment |
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Hi Ben,
On Wed, 12 Jun 2019 06:16:05 +0100, Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote: > > pci_msi_create_irq_domain -> pci_msi_domain_update_chip_ops will > set those two already since the driver sets MSI_FLAG_USE_DEF_CHIP_OPS > > Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> > --- > > [UNTESTED] > > Just something I noticed while browsing through those drivers in > search of ways to factor some of the code. > > That leads to a question here: > > Some MSI drivers such as this one (or any using the defaults mask/unmask > provided by drivers/pci/msi.c) only call the PCI MSI mask/unmask functions. > > Some other drivers call those PCI function but *also* call the parent > mask/unmask (giv-v2m for example) which generally is the inner domain > which just itself forwards to its own parent. > > Is there any preference for doing it one way or the other ? I can see > that in cases where the device doesn't support MSI masking, calling the > parent could be useful but we don't know that at the moment in the > corresponding code. > > It feels like something we should consolidate (and remove code from > drivers). For example, the defaults in drivers/pci/msi.c could always > call the parent if it exists and has a mask/unmask callback. > > Opinions ? I'm happy to produce patches once we agree... > > diff --git a/drivers/irqchip/irq-armada-370-xp.c b/drivers/irqchip/irq-armada-370-xp.c > index c9bdc5221b82..911230f28e2d 100644 > --- a/drivers/irqchip/irq-armada-370-xp.c > +++ b/drivers/irqchip/irq-armada-370-xp.c > @@ -197,8 +197,6 @@ static void armada_370_xp_irq_unmask(struct irq_data *d) > > static struct irq_chip armada_370_xp_msi_irq_chip = { > .name = "MPIC MSI", > - .irq_mask = pci_msi_mask_irq, > - .irq_unmask = pci_msi_unmask_irq, > }; > > static struct msi_domain_info armada_370_xp_msi_domain_info = { >
It looks to me that masking at the PCI level is rather superfluous as long as the MSI controller HW has the capability to mask the interrupt on a per MSI basis. After all, most non MSI-X endpoint lack support for masking of individual vectors, so I think that we should just mask things at the irqchip level. This is also consistent with what you'd have to do for non-PCI MSI, where nothing standardises the MSI masking.
I think this is in effect a split in responsibilities:
- the end-point driver should (directly or indirectly) control the interrupt generation at the end-point level,
- the MSI controller driver should control the signalling of the MSI to the CPU.
The only case where we should rely on masking interrupts at the end-point level is when the MSI controller doesn't provide a method to do so (hopefully a rare exception).
To take the example of the gicv2m driver that you mention above, I'd suggest the following:
diff --git a/drivers/irqchip/irq-gic-v2m.c b/drivers/irqchip/irq-gic-v2m.c index 3c77ab676e54..2ce801207acd 100644 --- a/drivers/irqchip/irq-gic-v2m.c +++ b/drivers/irqchip/irq-gic-v2m.c @@ -72,22 +72,10 @@ struct v2m_data { u32 flags; /* v2m flags for specific implementation */ }; -static void gicv2m_mask_msi_irq(struct irq_data *d) -{ - pci_msi_mask_irq(d); - irq_chip_mask_parent(d); -} - -static void gicv2m_unmask_msi_irq(struct irq_data *d) -{ - pci_msi_unmask_irq(d); - irq_chip_unmask_parent(d); -} - static struct irq_chip gicv2m_msi_irq_chip = { .name = "MSI", - .irq_mask = gicv2m_mask_msi_irq, - .irq_unmask = gicv2m_unmask_msi_irq, + .irq_mask = irq_chip_mask_parent, + .irq_unmask = irq_chip_unmask_parent, .irq_eoi = irq_chip_eoi_parent, .irq_write_msi_msg = pci_msi_domain_write_msg, }; The same should be applied to a number of drivers in the tree, which seem to have cargo-culted the wrong idiom (and I take responsibility for that).
Thanks,
M.
-- Jazz is not dead, it just smells funny.
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