Re: [PATCH V6] acpi: add support for extended IRQ to PCI link

Bjorn Helgaas
2015-11-30T20:38:29Z

On Wed, Nov 25, 2015 at 01:52:38PM -0500, Sinan Kaya wrote:
> The ACPI compiler uses the extended format when used interrupt numbers
> are greater than 256. The extended IRQ numbers use 32 bits for storing
> interrupts. The code already supports parsing extended IRQ type but is
> limited by 256 due to used data structure type (u8). This patch changes
> the interrupt number type to 32 bits and places an upper limit of 1020
> as possible interrupt id. 1020 is the maximum interrupt ID that can be
> assigned to an ARM SPI interrupt according to ARM architecture.
>
> Additional checks have been placed to return an error when ACPI_MAX_IRQS
> is exceeded.
>
> Signed-off-by: Sinan Kaya <okaya@codeaurora.org>

I don't think the description is quite accurate -- I think the
extended IRQ descriptor is required for IRQs of *16* and greater, not
IRQs greater than 256. Here's how I understand it:

The ACPI IRQ Descriptor contains a 16-bit mask with a bit for each
IRQ, so it can describe interrupt numbers in the range [0-15].
Interrupt numbers greater than 15 must be described with an Extended
IRQ Descriptor, which contains a table of 32-bit interrupt numbers
and can describe interrupt numbers in the range [0-(2^32-1)]. See
ACPI 5.0, sections 6.4.2.1 and 6.4.3.6.

> ---
> drivers/acpi/pci_link.c | 29 ++++++++++++++++++++++++-----
> 1 file changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
> index 7c8408b..5ab83dc 100644
> --- a/drivers/acpi/pci_link.c
> +++ b/drivers/acpi/pci_link.c
> @@ -4,6 +4,7 @@
> * Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
> * Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
> * Copyright (C) 2002 Dominik Brodowski <devel@brodo.de>
> + * Copyright (c) 2015, The Linux Foundation. All rights reserved.
> *
> * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> *
> @@ -47,6 +48,14 @@ ACPI_MODULE_NAME("pci_link");
> #define ACPI_PCI_LINK_FILE_STATUS "state"
> #define ACPI_PCI_LINK_MAX_POSSIBLE 16
>
> +/*
> + * 1020 is the maximum interrupt ID that can be assigned to
> + * an ARM SPI interrupt according to ARM architecture.
> + */
> +#define ACPI_MAX_IRQS 1020
> +#define ACPI_MAX_ISA_IRQ 16

ACPI_MAX_IRQS is only used to size the acpi_irq_penalty[] table (and
after your patch, to validate IRQ numbers from ACPI). But I think the
acpi_irq_penalty[] table is a design we've outgrown. I *think* we
only care about penalties for IRQs 0-15, so even a 256-entry table is
more than we need.

If we could make acpi_irq_penalty[] a fixed size of 16 entries or
replace it with a linked list, I think we could get rid of
ACPI_MAX_IRQS completely. Then the validation checks you add below
would be unnecessary and we could handle any interrupt number supplied
from ACPI.

Bjorn

> +
> +
> static int acpi_pci_link_add(struct acpi_device *device,
> const struct acpi_device_id *not_used);
> static void acpi_pci_link_remove(struct acpi_device *device);
> @@ -67,12 +76,12 @@ static struct acpi_scan_handler pci_link_handler = {
> * later even the link is disable. Instead, we just repick the active irq
> */
> struct acpi_pci_link_irq {
> - u8 active; /* Current IRQ */
> + u32 active; /* Current IRQ */
> u8 triggering; /* All IRQs */
> u8 polarity; /* All IRQs */
> u8 resource_type;
> u8 possible_count;
> - u8 possible[ACPI_PCI_LINK_MAX_POSSIBLE];
> + u32 possible[ACPI_PCI_LINK_MAX_POSSIBLE];
> u8 initialized:1;
> u8 reserved:7;
> };
> @@ -147,6 +156,13 @@ static acpi_status acpi_pci_link_check_possible(struct acpi_resource *resource,
> p->interrupts[i]);
> continue;
> }
> + if (p->interrupts[i] >= ACPI_MAX_IRQS) {
> + dev_warn(&link->device->dev,
> + "Ignoring IRQ(%d) as it exceeds max(%d)\n",
> + p->interrupts[i],
> + ACPI_MAX_IRQS - 1);
> + continue;
> + }
> link->irq.possible[i] = p->interrupts[i];
> link->irq.possible_count++;
> }
> @@ -279,6 +295,12 @@ static int acpi_pci_link_get_current(struct acpi_pci_link *link)
> result = -ENODEV;
> }
>
> + if (irq >= ACPI_MAX_IRQS) {
> + dev_err(&link->device->dev,
> + "Ignoring IRQ(%d) as it exceeds max(%d)\n",
> + irq, ACPI_MAX_IRQS - 1);
> + result = -ENODEV;
> + }
> link->irq.active = irq;
>
> ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Link at IRQ %d \n", link->irq.active));
> @@ -437,9 +459,6 @@ static int acpi_pci_link_set(struct acpi_pci_link *link, int irq)
> * enabled system.
> */
>
> -#define ACPI_MAX_IRQS 256
> -#define ACPI_MAX_ISA_IRQ 16
> -
> #define PIRQ_PENALTY_PCI_AVAILABLE (0)
> #define PIRQ_PENALTY_PCI_POSSIBLE (16*16)
> #define PIRQ_PENALTY_PCI_USING (16*16*16)
> --
> Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
>
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