PCI IRQ resource deallocation support [2/3]

This patch is ACPI portion of IRQ deallocation. This patch defines the following new interface. The implementation of this interface depends on each platform.

o void acpi_unregister_gsi(int irq)

This is a opposite portion of acpi_register_gsi(). This has a responsibility for deallocating IRQ resources associated with the specified linux IRQ number.

We need to consider the case of shared interrupt. In the case of shared interrupt, acpi_register_gsi() is called multiple times for one gsi. That is, registrations and unregistrations can be nested.

This function undoes the effect of one call to acpi_register_gsi(). If this matches the last registration, IRQ resources associated with the specified linux IRQ number are freed.

This patch also adds the following new function.

o void acpi_pci_irq_disable (struct pci_dev *dev)

This function is a opposite portion of acpi_pci_enable_irq(). It clears the device's linux IRQ number and calls acpi_unregister_gsi() to deallocate IRQ resources.

---

 linux-2.6.9-rc2-mm1-kanesige/arch/i386/kernel/acpi/boot.c |   11 +++++
 linux-2.6.9-rc2-mm1-kanesige/arch/ia64/kernel/acpi.c      |   11 +++++
 linux-2.6.9-rc2-mm1-kanesige/drivers/acpi/pci_irq.c       |   26 ++++++++++++++
 linux-2.6.9-rc2-mm1-kanesige/include/linux/acpi.h         |    2 +
 4 files changed, 50 insertions(+)

diff -puN arch/i386/kernel/acpi/boot.c~IRQ_deallocation_acpi arch/i386/kernel/acpi/boot.c
@@ -480,6 +480,17 @@ unsigned int acpi_register_gsi(u32 gsi, 
 }
 EXPORT_SYMBOL(acpi_register_gsi);
 
+/*
+ * This function undoes the effect of one call to acpi_register_gsi().
+ * If this matches the last regstration, any IRQ resources for gsi
+ * associated with the irq are freed.
+ */
+void
+acpi_unregister_gsi (unsigned int irq)
+{
+}
+EXPORT_SYMBOL(acpi_unregister_gsi);
+
 static unsigned long __init
 acpi_scan_rsdp (
 	unsigned long		start,

diff -puN arch/ia64/kernel/acpi.c~IRQ_deallocation_acpi arch/ia64/kernel/acpi.c
@@ -516,6 +516,17 @@ acpi_register_gsi (u32 gsi, int edge_lev
 }
 EXPORT_SYMBOL(acpi_register_gsi);
 
+/*
+ * This function undoes the effect of one call to acpi_register_gsi().
+ * If this matches the last regstration, any IRQ resources for gsi
+ * associated with the irq are freed.
+ */
+void
+acpi_unregister_gsi (unsigned int irq)
+{
+}
+EXPORT_SYMBOL(acpi_unregister_gsi);
+
 static int __init
 acpi_parse_fadt (unsigned long phys_addr, unsigned long size)
 {

diff -puN drivers/acpi/pci_irq.c~IRQ_deallocation_acpi drivers/acpi/pci_irq.c
@@ -390,3 +390,29 @@ acpi_pci_irq_enable (
 
 	return_VALUE(dev->irq);
 }
+
+void
+acpi_pci_irq_disable (
+	struct pci_dev		*dev)
+{
+	unsigned char irq_disabled, irq;
+
+	ACPI_FUNCTION_TRACE("acpi_pci_irq_disable");
+
+	irq_disabled = dev->irq;
+
+	/*
+	 * dev->irq is cleared by BIOS-assigned IRQ set during boot.
+	 */
+	pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &irq);
+	if (irq)
+		pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &irq);
+	dev->irq = irq;
+
+	printk(KERN_INFO PREFIX "PCI interrupt for device %s disabled\n",
+	       pci_name(dev));
+
+	acpi_unregister_gsi(irq_disabled);
+
+	return_VOID;
+}

diff -puN include/linux/acpi.h~IRQ_deallocation_acpi include/linux/acpi.h
@@ -414,6 +414,7 @@ static inline int acpi_boot_init(void)
 #endif 	/*!CONFIG_ACPI_BOOT*/
 
 unsigned int acpi_register_gsi (u32 gsi, int edge_level, int active_high_low);
+void acpi_unregister_gsi (unsigned int);
 int acpi_gsi_to_irq (u32 gsi, unsigned int *irq);
 
 #ifdef CONFIG_ACPI_PCI

@@ -439,6 +440,7 @@ extern struct acpi_prt_list	acpi_prt;
 struct pci_dev;
 
 int acpi_pci_irq_enable (struct pci_dev *dev);
+void acpi_pci_irq_disable (struct pci_dev *dev);
 
 struct acpi_pci_driver {
 	struct acpi_pci_driver *next;

_

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s/regstration/registration/ (also other occurrences below).

Hi Bjorn,

Thank you for your feedbacks.

Oops..
I'll fix these.

I'll fix this, thanks.

I had been considering what the "undefined dev->irq" was. In fact, I had other ideas that was clearing it by zero or -1 (0xffffffff). But I didn't know if we can use these values as a undefined IRQ number. So I'm clearing it by the value which was assigned by PCI core code (pci_read_irq()) before acpi_pci_irq_enable() was called.

How do you think?

Thanks,
Kenji Kaneshige

From: Kenji Kaneshige <[email protected]>
Subject: Re: [ACPI] [PATCH] PCI IRQ resource deallocation support [2/3]
Date: Wed, 22 Sep 2004 10:24:40 +0900

I think it has little sense in restoring value from the configuration space to dev->irq or clearing it.

If we do preventive programming, it may be worth
trying to define some magic constant (e.g. PCI_UNDEFINED_IRQ) and panic/BUG when the irq is being enabled.
Otherwise, leaving dev->irq as it is would be ok.

---
Takayoshi Kochi <t-kochi-UDFczIW9X1d8UrSeD/[email protected]>

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Hi Takayoshi,

Thank you for feedback.

Hmm, I think you are right.
I'll change my patch to leave dev->irq as it is. And then I'll investigate about defining PCI_UNDEFINED_IRQ.

In fact, I posted updated patches a little before. I'll re-post it with your feedback :-)

Thanks,
Kenji Kaneshige

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Some platforms (arm, arm26, ppc64) define a macro NO_IRQ:

include/asm-arm/irq.h:#define NO_IRQ        ((unsigned int)(-1))
include/asm-arm26/irq.h:#define NO_IRQ      ((unsigned int)(-1))
include/asm-ppc64/irq.h:#define NO_IRQ      (-1)

Thanks
Guennadi
---
Guennadi Liakhovetski

Hi Guennadi Liakhovetski,

Thank you for the information.
I refer to arm, arm26 and ppc64 codes.

Thanks,
Kenji Kaneshige