Re: [PATCH v1 1/1] x86/PCI: Introduce pcibios_is_irq_managed() helper

Bjorn Helgaas
2021-08-02T23:16:51Z

On Fri, Jul 30, 2021 at 11:53:55PM +0300, Andy Shevchenko wrote:
> The check for irq_managed flag along with non-zero irq is an idiom
> for x86 PCI implementation. Introduce helper and switch users over
> using it.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> arch/x86/include/asm/pci.h | 4 ++++
> arch/x86/pci/intel_mid_pci.c | 5 ++---
> arch/x86/pci/irq.c | 4 ++--
> drivers/acpi/pci_irq.c | 4 ++--
> 4 files changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/include/asm/pci.h b/arch/x86/include/asm/pci.h
> index d2c76c8d8cfd..ac25470c9558 100644
> --- a/arch/x86/include/asm/pci.h
> +++ b/arch/x86/include/asm/pci.h
> @@ -92,6 +92,10 @@ void pcibios_scan_root(int bus);
> struct irq_routing_table *pcibios_get_irq_routing_table(void);
> int pcibios_set_irq_routing(struct pci_dev *dev, int pin, int irq);
>
> +static inline bool pcibios_irq_is_managed(struct pci_dev *dev)
> +{
> + return dev->irq_managed && dev->irq > 0;
> +}
>
> #define HAVE_PCI_MMAP
> #define arch_can_pci_mmap_wc() pat_enabled()
> diff --git a/arch/x86/pci/intel_mid_pci.c b/arch/x86/pci/intel_mid_pci.c
> index f04742caf62b..0da287bcabf5 100644
> --- a/arch/x86/pci/intel_mid_pci.c
> +++ b/arch/x86/pci/intel_mid_pci.c
> @@ -230,7 +230,7 @@ static int intel_mid_pci_irq_enable(struct pci_dev *dev)
> int ret;
> u8 gsi;
>
> - if (dev->irq_managed && dev->irq > 0)
> + if (pcibios_irq_is_managed(dev))
> return 0;
>
> ret = pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &gsi);
> @@ -290,8 +290,7 @@ static int intel_mid_pci_irq_enable(struct pci_dev *dev)
>
> static void intel_mid_pci_irq_disable(struct pci_dev *dev)
> {
> - if (!mp_should_keep_irq(&dev->dev) && dev->irq_managed &&
> - dev->irq > 0) {
> + if (pcibios_irq_is_managed(dev) && !mp_should_keep_irq(&dev->dev)) {
> mp_unmap_irq(dev->irq);
> dev->irq_managed = 0;
> }
> diff --git a/arch/x86/pci/irq.c b/arch/x86/pci/irq.c
> index d3a73f9335e1..ce3927b68f9e 100644
> --- a/arch/x86/pci/irq.c
> +++ b/arch/x86/pci/irq.c
> @@ -1210,7 +1210,7 @@ static int pirq_enable_irq(struct pci_dev *dev)
> struct pci_dev *temp_dev;
> int irq;
>
> - if (dev->irq_managed && dev->irq > 0)
> + if (pcibios_irq_is_managed(dev))
> return 0;
>
> irq = IO_APIC_get_PCI_irq_vector(dev->bus->number,
> @@ -1280,7 +1280,7 @@ bool mp_should_keep_irq(struct device *dev)
> static void pirq_disable_irq(struct pci_dev *dev)
> {
> if (io_apic_assign_pci_irqs && !mp_should_keep_irq(&dev->dev) &&
> - dev->irq_managed && dev->irq) {
> + pcibios_irq_is_managed(dev)) {
> mp_unmap_irq(dev->irq);
> dev->irq = 0;
> dev->irq_managed = 0;
> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
> index b63954c36e86..b463bdd2dbb5 100644
> --- a/drivers/acpi/pci_irq.c
> +++ b/drivers/acpi/pci_irq.c
> @@ -397,7 +397,7 @@ int __acpi_pci_irq_enable(struct pci_dev *dev, int polarity)
> return 0;
> }
>
> - if (dev->irq_managed && dev->irq > 0)
> + if (pcibios_irq_is_managed(dev))
> return 0;
>
> entry = acpi_pci_irq_lookup(dev, pin);
> @@ -486,7 +486,7 @@ void acpi_pci_irq_disable(struct pci_dev *dev)
> u8 pin;
>
> pin = dev->pin;
> - if (!pin || !dev->irq_managed || dev->irq <= 0)
> + if (!pin || !pcibios_irq_is_managed(dev))

This file may be compiled for x86, arm64, and ia64, but it looks like
you only defined pcibios_irq_is_managed() for x86.

We used to have a generic pci_has_managed_irq() that was the same as
your pcibios_irq_is_managed(), but it was removed by 67b4eab91caf
("Revert "PCI: Add helpers to manage pci_dev->irq and
pci_dev->irq_managed"").

I'm sorry that pdev->irq_managed got added without a comment by
cffe0a2b5a34 ("x86, irq: Keep balance of IOAPIC pin reference count").
Even reading that commit log, I'm not sure exactly what it means. The
log says:

So flag irq_managed is introduced to track whether IRQ number is
assigned by OS and to protect pirq_enable_irq(), acpi_pci_irq_enable()
and intel_mid_pci_irq_enable() from reentrance.

> return;
>
> /* Keep IOAPIC pin configuration when suspending */
> --
> 2.30.2
>