linux-kernel - Re: [PATCH V3 1/3] ACPI, PCI IRQ: add PCI_USING penalty for ISA interrupts

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Date:   Sat, 22 Oct 2016 18:58:37 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     linux-acpi@...r.kernel.org, rjw@...ysocki.net, bhelgaas@...gle.com,
        ravikanth.nalla@....com, linux@...nbow-software.org,
        timur@...eaurora.org, cov@...eaurora.org, jcm@...hat.com,
        alex.williamson@...hat.com, linux-pci@...r.kernel.org,
        agross@...eaurora.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, wim@....tudelft.nl,
        linux-arm-kernel@...ts.infradead.org, Len Brown <lenb@...nel.org>
Subject: Re: [PATCH V3 1/3] ACPI, PCI IRQ: add PCI_USING penalty for ISA
 interrupts

On Sat, Oct 15, 2016 at 12:31:05AM -0400, Sinan Kaya wrote:
> The change introduced in commit 103544d86976 ("ACPI,PCI,IRQ: reduce
> resource requirements") removed PCI_USING penalty from
> acpi_pci_link_allocate function as there is no longer a fixed size penalty
> array for both PCI interrupts greater than 16.
> 
> The array size has been reduced to 16 and array name got prefixed as ISA
> since it only is accountable for the ISA interrupts.
> 
> The original change in commit 103544d86976 ("ACPI,PCI,IRQ: reduce
> resource requirements") removed penalty assignment in the code for PCI
> thinking that we will add the penalty later in acpi_irq_pci_sharing_penalty
> function.
> 
> However, this function only gets called if the IRQ number is greater than
> 16 and acpi_irq_get_penalty function gets called before ACPI start in
> acpi_isa_irq_available and acpi_penalize_isa_irq functions. We can't rely
> on iterating the link list.
> 
> We need to add the PCI_USING penalty for ISA interrupts too if the link is
> in use and matches our ISA IRQ number.

I think the history about the array size is more than is necessary for this
changelog.  I think the useful part is something like this:

  ACPI: pci_link: Include PIRQ_PENALTY_PCI_USING for ISA IRQs

  103544d86976 ("ACPI,PCI,IRQ: reduce resource requirements") replaced
  the addition of PIRQ_PENALTY_PCI_USING in acpi_pci_link_allocate()
  with an addition in acpi_irq_pci_sharing_penalty(), but f7eca374f000
  ("ACPI,PCI,IRQ: separate ISA penalty calculation") removed the use
  of acpi_irq_pci_sharing_penalty() for ISA IRQs.

  Therefore, PIRQ_PENALTY_PCI_USING is missing from ISA IRQs used by
  interrupt links.  Include that penalty by adding it in the
  acpi_pci_link_allocate() path.

  Fixes: f7eca374f000 ("ACPI,PCI,IRQ: separate ISA penalty calculation")

> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
>  drivers/acpi/pci_link.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
> index c983bf7..a212709 100644
> --- a/drivers/acpi/pci_link.c
> +++ b/drivers/acpi/pci_link.c
> @@ -619,6 +619,10 @@ static int acpi_pci_link_allocate(struct acpi_pci_link *link)
>  			    acpi_device_bid(link->device));
>  		return -ENODEV;
>  	} else {
> +		if (link->irq.active < ACPI_MAX_ISA_IRQS)
> +			acpi_isa_irq_penalty[link->irq.active] +=
> +				PIRQ_PENALTY_PCI_USING;
> +
>  		printk(KERN_WARNING PREFIX "%s [%s] enabled at IRQ %d\n",
>  		       acpi_device_name(link->device),
>  		       acpi_device_bid(link->device), link->irq.active);
> -- 
> 1.9.1
> 
> 
> _______________________________________________
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> linux-arm-kernel@...ts.infradead.org
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