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Date: Mon, 15 Feb 2016 12:53:18 +0800
From: Chen Fan <chen.fan.fnst@...fujitsu.com>
To: <linux-acpi@...r.kernel.org>
CC: <linux-kernel@...r.kernel.org>, <rjw@...ysocki.net>,
<lenb@...nel.org>, <bhelgaas@...gle.com>, <rafael@...nel.org>
Subject: Re: [PATCH v5] x86/PCI: Recognize that Interrupt Line 255 means "not
connected"
Oh, it's my fault to send this wrong patch, so sorry for that. pls
ignore this patch.
I has tested the new patch, it works fine on my environment. I have
resent it.
Thanks,
Chen
On 02/15/2016 11:25 AM, Chen Fan wrote:
> Per the x86-specific footnote to PCI spec r3.0, sec 6.2.4, the value 255 in
> the Interrupt Line register means "unknown" or "no connection."
> Previously, when we couldn't derive an IRQ from the _PRT, we fell back to
> using the value from Interrupt Line as an IRQ. It's questionable whether
> we should do that at all, but the spec clearly suggests we shouldn't do it
> for the value 255 on x86.
>
> Calling request_irq() with IRQ 255 may succeed, but the driver won't
> receive any interrupts. Or, if IRQ 255 is shared with another device, it
> may succeed, and the driver's ISR will be called at random times when the
> *other* device interrupts. Or it may fail if another device is using IRQ
> 255 with incompatible flags. What we *want* is for request_irq() to fail
> predictably so the driver can fall back to polling.
>
> On x86, assume 255 in the Interrupt Line means the INTx line is not
> connected. In that case, set dev->irq to IRQ_NOTCONNECTED so request_irq()
> will fail gracefully with -ENOTCONN.
>
> We found this problem on a system where Secure Boot firmware assigned
> Interrupt Line 255 to an i801_smbus device and another device was already
> using MSI-X IRQ 255. This was in v3.10, where i801_probe() fails if
> request_irq() fails:
>
> i801_smbus 0000:00:1f.3: enabling device (0140 -> 0143)
> i801_smbus 0000:00:1f.3: can't derive routing for PCI INT C
> i801_smbus 0000:00:1f.3: PCI INT C: no GSI
> genirq: Flags mismatch irq 255. 00000080 (i801_smbus) vs. 00000000 (megasa)
> CPU: 0 PID: 2487 Comm: kworker/0:1 Not tainted 3.10.0-229.el7.x86_64 #1
> Hardware name: FUJITSU PRIMEQUEST 2800E2/D3736, BIOS PRIMEQUEST 2000 Serie5
> Call Trace:
> dump_stack+0x19/0x1b
> __setup_irq+0x54a/0x570
> request_threaded_irq+0xcc/0x170
> i801_probe+0x32f/0x508 [i2c_i801]
> local_pci_probe+0x45/0xa0
> i801_smbus 0000:00:1f.3: Failed to allocate irq 255: -16
> i801_smbus: probe of 0000:00:1f.3 failed with error -16
>
> After aeb8a3d16ae0 ("i2c: i801: Check if interrupts are disabled"),
> i801_probe() will fall back to polling if request_irq() fails. But we
> still need this patch because request_irq() may succeed or fail depending
> on other devices in the system. If request_irq() fails, i801_smbus will
> work by falling back to polling, but if it succeeds, i801_smbus won't work
> because it expects interrupts that it may not receive.
>
> Signed-off-by: Chen Fan <chen.fan.fnst@...fujitsu.com>
> Acked-by: Thomas Gleixner <tglx@...utronix.de>
> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
> ---
> drivers/acpi/pci_irq.c | 29 +++++++++++++++++++++++++----
> include/linux/interrupt.h | 10 ++++++++++
> kernel/irq/manage.c | 9 ++++++++-
> 3 files changed, 43 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
> index d30184c..0227cc6 100644
> --- a/drivers/acpi/pci_irq.c
> +++ b/drivers/acpi/pci_irq.c
> @@ -33,6 +33,7 @@
> #include <linux/pci.h>
> #include <linux/acpi.h>
> #include <linux/slab.h>
> +#include <linux/interrupt.h>
>
> #define PREFIX "ACPI: "
>
> @@ -387,6 +388,23 @@ static inline int acpi_isa_register_gsi(struct pci_dev *dev)
> }
> #endif
>
> +static inline bool acpi_pci_irq_valid(struct pci_dev *dev)
> +{
> +#ifdef CONFIG_X86
> + /*
> + * On x86 irq line 0xff means "unknown" or "no connection"
> + * (PCI 3.0, Section 6.2.4, footnote on page 223).
> + */
> + if (dev->irq == 0xff) {
> + dev->irq = IRQ_NOTCONNECTED;
> + dev_warn(&dev->dev, "PCI INT %c: not connected\n",
> + pin_name(pin));
> + return false;
> + }
> +#endif
> + return true;
> +}
> +
> int acpi_pci_irq_enable(struct pci_dev *dev)
> {
> struct acpi_prt_entry *entry;
> @@ -431,11 +449,14 @@ int acpi_pci_irq_enable(struct pci_dev *dev)
> } else
> gsi = -1;
>
> - /*
> - * No IRQ known to the ACPI subsystem - maybe the BIOS /
> - * driver reported one, then use it. Exit in any case.
> - */
> if (gsi < 0) {
> + /*
> + * No IRQ known to the ACPI subsystem - maybe the BIOS /
> + * driver reported one, then use it. Exit in any case.
> + */
> + if (!acpi_pci_irq_valid(dev, pin))
> + return 0;
> +
> if (acpi_isa_register_gsi(dev))
> dev_warn(&dev->dev, "PCI INT %c: no GSI\n",
> pin_name(pin));
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index cb30edb..12f7da4 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -125,6 +125,16 @@ struct irqaction {
>
> extern irqreturn_t no_action(int cpl, void *dev_id);
>
> +/*
> + * If a (PCI) device interrupt is not connected we set dev->irq to
> + * IRQ_NOTCONNECTED. This causes request_irq() to fail with -ENOTCONN, so we
> + * can distingiush that case from other error returns.
> + *
> + * 0x80000000 is guaranteed to be outside the available range of interrupts
> + * and easy to distinguish from other possible incorrect values.
> + */
> +#define IRQ_NOTCONNECTED (1U << 31)
> +
> extern int __must_check
> request_threaded_irq(unsigned int irq, irq_handler_t handler,
> irq_handler_t thread_fn,
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index 8411872..e79e60f 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -1609,6 +1609,9 @@ int request_threaded_irq(unsigned int irq, irq_handler_t handler,
> struct irq_desc *desc;
> int retval;
>
> + if (irq == IRQ_NOTCONNECTED)
> + return -ENOTCONN;
> +
> /*
> * Sanity-check: shared interrupts must pass in a real dev-ID,
> * otherwise we'll have trouble later trying to figure out
> @@ -1699,9 +1702,13 @@ EXPORT_SYMBOL(request_threaded_irq);
> int request_any_context_irq(unsigned int irq, irq_handler_t handler,
> unsigned long flags, const char *name, void *dev_id)
> {
> - struct irq_desc *desc = irq_to_desc(irq);
> + struct irq_desc *desc;
> int ret;
>
> + if (irq == IRQ_NOTCONNECTED)
> + return -ENOTCONN;
> +
> + desc = irq_to_desc(irq);
> if (!desc)
> return -EINVAL;
>
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