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

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Date:   Tue, 18 Oct 2016 08:59:12 -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.

It seems wrong to me that we call acpi_irq_get_penalty() from
acpi_irq_penalty_update() and acpi_penalize_isa_irq().  It seems like they
should just manipulate acpi_isa_irq_penalty[irq] directly.

acpi_irq_penalty_update() is for command-line parameters, so it certainly
doesn't need the acpi_irq_pci_sharing_penalty() information (the
acpi_link_list should be empty at the time we process the command-line
parameters).

acpi_penalize_isa_irq() is telling us that a PNP or ACPI device is using
the IRQ -- this should modify the IRQ's penalty, but it shouldn't depend on
the acpi_irq_pci_sharing_penalty() value at all.

> We need to add the PCI_USING penalty for ISA interrupts too if the link is
> in use and matches our ISA IRQ number.
> 
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> ---
>  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
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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