Hi Sinan,
On Wed, Jun 29, 2016 at 04:27:37AM -0400, Sinan Kaya wrote:
> Since commit 103544d86976 ("ACPI,PCI,IRQ: reduce resource requirements")
> the penalty values are calculated on the fly rather than boot time.
>
> This works fine for PCI interrupts but not so well for the ISA interrupts.
> Whether an ISA interrupt is in use or not information is not available
> inside the pci_link.c file. This information gets sent externally via
> acpi_penalize_isa_irq function. If active is true, then the IRQ is in use
> by ISA. Otherwise, IRQ is in use by PCI.
>
> Since the current code relies on PCI Link object for determination of
> penalties, we are factoring in the PCI penalty twice after
> acpi_penalize_isa_irq function is called.
I know this patch has already been merged, but I'm confused.
Can you be a little more specific about how we factor in the PCI
penalty twice? I think that when we enumerate an enabled link device,
we call acpi_penalize_isa_irq(x) in this path:
pnpacpi_allocated_resource
pnpacpi_add_irqresource
pcibios_penalize_isa_irq
acpi_penalize_isa_irq
acpi_isa_irq_penalty[x] = PIRQ_PENALTY_ISA_USED
And I see that acpi_irq_penalty_init() also adds in some penalty
(either "PIRQ_PENALTY_PCI_POSSIBLE / possible_count" or
PIRQ_PENALTY_PCI_POSSIBLE). And when we call acpi_irq_get_penalty(x),
we add in PIRQ_PENALTY_PCI_USING.
It doesn't seem right to me that we're adding both
PIRQ_PENALTY_ISA_USED and PIRQ_PENALTY_PCI_USING. Is that the problem
you're referring to?
> This change is limiting the newly added functionality to just PCI
> interrupts so that old behavior is still maintained.
>
> Signed-off-by: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
> ---
> drivers/acpi/pci_link.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
> index 714ba4d..8c08971 100644
> --- a/drivers/acpi/pci_link.c
> +++ b/drivers/acpi/pci_link.c
> @@ -496,9 +496,6 @@ static int acpi_irq_get_penalty(int irq)
> {
> int penalty = 0;
>
> - if (irq < ACPI_MAX_ISA_IRQS)
> - penalty += acpi_isa_irq_penalty[irq];
> -
> /*
> * Penalize IRQ used by ACPI SCI. If ACPI SCI pin attributes conflict
> * with PCI IRQ attributes, mark ACPI SCI as ISA_ALWAYS so it won't be
> @@ -513,6 +510,9 @@ static int acpi_irq_get_penalty(int irq)
> penalty += PIRQ_PENALTY_PCI_USING;
> }
>
> + if (irq < ACPI_MAX_ISA_IRQS)
> + return penalty + acpi_isa_irq_penalty[irq];
> +
> penalty += acpi_irq_pci_sharing_penalty(irq);
> return penalty;
I don't understand what's going on here.
acpi_irq_pci_sharing_penalty(X) basically tells us how many link
devices are already using IRQ X. This change makes it so we don't
consider that information if X < ACPI_MAX_ISA_IRQS.
Let's say we have several link devices that are initially disabled,
e.g.,
LNKA (IRQs 9 10 11)
LNKB (IRQs 9 10 11)
LNKC (IRQs 9 10 11)
When we enable these, I think we'll choose the same IRQ for all of
them because we no longer look at the other links to see how they're
configured.
> }
> --
> 1.8.2.1
>
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