Subject: [PATCH V4 2/3] Revert "ACPI,PCI,IRQ: remove SCI penalize function"

From: [email-masked] (Bjorn Helgaas)
Date: Thu, 20 Oct 2016 20:58:14 -0500

On Wed, Oct 19, 2016 at 06:21:03PM -0400, Sinan Kaya wrote:
> The SCI penalize function was removed in two steps (first refactor
> and then remove) and these changes are reverted here in one go.
> 
> The commit 103544d86976 ("ACPI,PCI,IRQ: reduce resource requirements")
> refactored the original code so that SCI penalty is calculated dynamically
> by the time get_penalty function is called. That change is partially
> reverted here, specifically for the SCI IRQ alone.
> 
> The SCI penalize function was finally dropped by commit 9e5ed6d1fb87
> ("ACPI,PCI,IRQ: remove SCI penalize function") that replaced the old SCI
> penalty API with penalty calculation carried out dynamically and based
> on the acpi_gbl_FADT.sci_interrupt value.
> 
> However, that new algorithm relies on the accurate setting of IRQ
> types and that doesn't happen early enough on some platforms which
> leads to incorrect penalty assignments for PCI IRQs.  In those cases,
> irq_get_trigger_type() returns incorrect values for the IRQs in
> question, because they have not been registered yet by the time the
> penalties are calculated.
> 
> To fix this problem, we only need to fix the penalty for the SCI interrupt.
> It seems better to add a single "sci_penalty" variable, set it to
> PIRQ_PENALTY_PCI_USING if it's level/low or PIRQ_PENALTY_ISA_ALWAYS
> otherwise, and add "sci_penalty" in when appropriate.  That should fix it
> for *any* SCI IRQ, not just those less than 256, and we don't have to add
> these extra penalty table entries that are all unused (except possibly for
> one entry if we have an SCI in the 16-255 range).
> 
> For this reason, revert commit 9e5ed6d1fb87 ("ACPI,PCI,IRQ: remove SCI
> penalize function") completely to restore the correct behavior.

I like this patch fine, except for the changelog.  I don't think it's
useful to describe this as a revert and give all the historical
details.  I think the important part is something like this:

  We previously used irq_get_trigger_type(irq) to help compute the
  penalty for the SCI, but that depends on the SCI having been
  registered already.  Add acpi_penalize_sci_irq() so platforms can
  tell us the SCI IRQ, trigger, and polarity so we can compute the
  penalty even before the SCI has been registered.

Acked-by: Bjorn Helgaas <[email-masked]>

> Link: https://lkml.org/lkml/2016/10/4/283
> Signed-off-by: Sinan Kaya <[email-masked]>
> Fixes: commit 103544d86976 ("ACPI,PCI,IRQ: reduce resource requirements")
> Fixes: commit 9e5ed6d1fb87 ("ACPI,PCI,IRQ: remove SCI penalize function")

"commit" is redundant; it's sufficient to say:

  Fixes: 103544d86976 ("ACPI,PCI,IRQ: reduce resource requirements")

In fact, I don't think you really need to include "commit" in the
reference to 9e5ed6d1fb87 above either.

> ---
>  arch/x86/kernel/acpi/boot.c |  1 +
>  drivers/acpi/pci_link.c     | 30 +++++++++++++++---------------
>  include/linux/acpi.h        |  1 +
>  3 files changed, 17 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> index 90d84c3..0ffd26e 100644
> --- a/arch/x86/kernel/acpi/boot.c
> +++ b/arch/x86/kernel/acpi/boot.c
> @@ -453,6 +453,7 @@ static void __init acpi_sci_ioapic_setup(u8 bus_irq, u16 polarity, u16 trigger,
>  		polarity = acpi_sci_flags & ACPI_MADT_POLARITY_MASK;
>  
>  	mp_override_legacy_irq(bus_irq, polarity, trigger, gsi);
> +	acpi_penalize_sci_irq(bus_irq, trigger, polarity);
>  
>  	/*
>  	 * stash over-ride to indicate we've been here
> diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
> index 4f37938..294b190 100644
> --- a/drivers/acpi/pci_link.c
> +++ b/drivers/acpi/pci_link.c
> @@ -87,6 +87,7 @@ struct acpi_pci_link {
>  
>  static LIST_HEAD(acpi_link_list);
>  static DEFINE_MUTEX(acpi_link_lock);
> +static int sci_irq = -1, sci_penalty;
>  
>  /* --------------------------------------------------------------------------
>                              PCI Link Device Management
> @@ -496,25 +497,13 @@ static int acpi_irq_get_penalty(int irq)
>  {
>  	int penalty = 0;
>  
> -	/*
> -	* 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
> -	* use for PCI IRQs.
> -	*/
> -	if (irq == acpi_gbl_FADT.sci_interrupt) {
> -		u32 type = irq_get_trigger_type(irq) & IRQ_TYPE_SENSE_MASK;
> -
> -		if (type != IRQ_TYPE_LEVEL_LOW)
> -			penalty += PIRQ_PENALTY_ISA_ALWAYS;
> -		else
> -			penalty += PIRQ_PENALTY_PCI_USING;
> -	}
> +	if (irq == sci_irq)
> +		penalty += sci_penalty;
>  
>  	if (irq < ACPI_MAX_ISA_IRQS)
>  		return penalty + acpi_isa_irq_penalty[irq];
>  
> -	penalty += acpi_irq_pci_sharing_penalty(irq);
> -	return penalty;
> +	return penalty + acpi_irq_pci_sharing_penalty(irq);
>  }
>  
>  int __init acpi_irq_penalty_init(void)
> @@ -881,6 +870,17 @@ bool acpi_isa_irq_available(int irq)
>  		    acpi_irq_get_penalty(irq) < PIRQ_PENALTY_ISA_ALWAYS);
>  }
>  
> +void acpi_penalize_sci_irq(int irq, int trigger, int polarity)
> +{
> +	sci_irq = irq;
> +
> +	if (trigger == ACPI_MADT_TRIGGER_LEVEL &&
> +	    polarity == ACPI_MADT_POLARITY_ACTIVE_LOW)
> +		sci_penalty = PIRQ_PENALTY_PCI_USING;
> +	else
> +		sci_penalty = PIRQ_PENALTY_ISA_ALWAYS;
> +}
> +
>  /*
>   * Over-ride default table to reserve additional IRQs for use by ISA
>   * e.g. acpi_irq_isa=5
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index c5eaf2f..67d1d3e 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -318,6 +318,7 @@ struct pci_dev;
>  int acpi_pci_irq_enable (struct pci_dev *dev);
>  void acpi_penalize_isa_irq(int irq, int active);
>  bool acpi_isa_irq_available(int irq);
> +void acpi_penalize_sci_irq(int irq, int trigger, int polarity);
>  void acpi_pci_irq_disable (struct pci_dev *dev);
>  
>  extern int ec_read(u8 addr, u8 *val);
> -- 
> 1.9.1
> 
> 
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