[RFC] irq handling code consolidation (common part)

["Andrey Panin" <pazke@orbita1.ru>]

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Hi all,

this patch moves some common parts of irq handling code to one place.
Arch specific patches will follow. Patch for i386 is tested and performed 
well, but other arch specific patched are not. Please take a look.

Please CC me answering this letter, I'm not subscribed to lkml currently.

Best regards.

-- 
Andrey Panin		| Embedded systems software developer
pazke@orbita1.ru	| PGP key: wwwkeys.pgp.net

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diff --minimal -urN -X /usr/share/dontdiff linux-2.5.52.vanilla/kernel/Makefile linux-2.5.52/kernel/Makefile
--- linux-2.5.52.vanilla/kernel/Makefile	Thu Dec 19 20:03:23 2002
+++ linux-2.5.52/kernel/Makefile	Tue Dec 24 19:36:44 2002
@@ -22,6 +22,7 @@
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_SOFTWARE_SUSPEND) += suspend.o
 obj-$(CONFIG_COMPAT) += compat.o
+obj-$(CONFIG_GENERIC_IRQ) += irq.o
 
 ifneq ($(CONFIG_IA64),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff --minimal -urN -X /usr/share/dontdiff linux-2.5.52.vanilla/kernel/irq.c linux-2.5.52/kernel/irq.c
--- linux-2.5.52.vanilla/kernel/irq.c	Thu Jan  1 03:00:00 1970
+++ linux-2.5.52/kernel/irq.c	Tue Dec 24 20:32:56 2002
@@ -0,0 +1,364 @@
+/*
+ *  linux/kernel/irq.c
+ *
+ *  Mostly architecture independent parts of IRQ handling.
+ *
+ *  Copyright (C) 1992, 2002 Linus Torvalds, Ingo Molnar.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ */
+
+#include <linux/config.h>
+#include <linux/irq.h>
+#include <linux/interrupt.h>
+#include <linux/random.h>
+
+/*
+ * Controller mappings for all interrupt sources:
+ */
+irq_desc_t irq_desc[NR_IRQS] __cacheline_aligned = {
+	[0 ... NR_IRQS - 1] = {
+		.handler =	&no_irq_type,
+		.lock =		SPIN_LOCK_UNLOCKED,
+	}
+};
+
+/*
+ * Special irq handlers.
+ */
+
+void no_action(int cpl, void *dev_id, struct pt_regs *regs) { }
+
+/*
+ * Generic no controller code
+ */
+atomic_t irq_err_count;
+
+static void no_irq_enable_disable(unsigned int irq) { }
+static unsigned int no_irq_startup(unsigned int irq) { return 0; }
+
+static void no_irq_ack(unsigned int irq)
+{
+	atomic_inc(&irq_err_count);
+	printk(KERN_CRIT "Unexpected IRQ trap at vector %u\n", irq);
+	ack_bad_irq(irq);
+}
+
+struct hw_interrupt_type no_irq_type = {
+	.typename	= "none",
+	.startup	= no_irq_startup,
+	.shutdown	= no_irq_enable_disable,
+	.enable		= no_irq_enable_disable,
+	.disable	= no_irq_enable_disable,
+	.ack		= no_irq_ack,
+	.end		= no_irq_enable_disable,
+};
+
+/*
+ * This should really return information about whether
+ * we should do bottom half handling etc. Right now we
+ * end up _always_ checking the bottom half, which is a
+ * waste of time and is not what some drivers would
+ * prefer.
+ */
+int handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
+		     struct irqaction *action)
+{
+	int status = 1;	/* Force the "do bottom halves" bit */
+
+	if (!(action->flags & SA_INTERRUPT))
+		local_irq_enable();
+
+	do {
+		status |= action->flags;
+		action->handler(irq, action->dev_id, regs);
+		action = action->next;
+	} while (action);
+	if (status & SA_SAMPLE_RANDOM)
+		add_interrupt_randomness(irq);
+	local_irq_disable();
+
+	return status;
+}
+
+#if defined(CONFIG_SMP) && !defined(HAVE_ARCH_SYNCRONIZE_IRQ)
+
+inline void synchronize_irq(unsigned int irq)
+{
+        /* is there anything to synchronize with? */
+	if (!irq_desc[irq].action)
+		return;
+
+	while (irq_desc[irq].status & IRQ_INPROGRESS)
+		cpu_relax();
+}
+
+#endif
+
+/*
+ * Generic enable/disable code: this just calls
+ * down into the PIC-specific version for the actual
+ * hardware disable after having gotten the irq
+ * controller lock. 
+ */
+ 
+/**
+ *	disable_irq_nosync - disable an irq without waiting
+ *	@irq: Interrupt to disable
+ *
+ *	Disable the selected interrupt line.  Disables and Enables are
+ *	nested.
+ *	Unlike disable_irq(), this function does not ensure existing
+ *	instances of the IRQ handler have completed before returning.
+ *
+ *	This function may be called from IRQ context.
+ */
+inline void disable_irq_nosync(unsigned int irq)
+{
+	irq_desc_t *desc = irq_desc(irq);
+	unsigned long flags;
+
+	spin_lock_irqsave(&desc->lock, flags);
+	if (!desc->depth++) {
+		desc->status |= IRQ_DISABLED;
+		desc->handler->disable(irq);
+	}
+	spin_unlock_irqrestore(&desc->lock, flags);
+}
+
+/**
+ *	disable_irq - disable an irq and wait for completion
+ *	@irq: Interrupt to disable
+ *
+ *	Disable the selected interrupt line.  Enables and Disables are
+ *	nested. That is for two disables you need two enables.
+ *	This function waits for any pending IRQ handlers for this interrupt
+ *	to complete before returning. If you use this function while
+ *	holding a resource the IRQ handler may need you will deadlock.
+ *
+ *	This function may be called - with care - from IRQ context.
+ */
+void disable_irq(unsigned int irq)
+{
+	disable_irq_nosync(irq);
+	synchronize_irq(irq);
+}
+
+/**
+ *	enable_irq - enable handling of an irq
+ *	@irq: Interrupt to enable
+ *
+ *	Undoes the effect of one call to disable_irq().  If this
+ *	matches the last disable, processing of interrupts on this
+ *	IRQ line is re-enabled.
+ *
+ *	This function may be called from IRQ context.
+ */
+void enable_irq(unsigned int irq)
+{
+	irq_desc_t *desc = irq_desc(irq);
+	unsigned long flags;
+
+	spin_lock_irqsave(&desc->lock, flags);
+	switch (desc->depth) {
+	case 1: {
+		unsigned int status = desc->status & ~IRQ_DISABLED;
+		desc->status = status;
+		if ((status & (IRQ_PENDING | IRQ_REPLAY)) == IRQ_PENDING) {
+			desc->status = status | IRQ_REPLAY;
+			hw_resend_irq(desc->handler,irq);
+		}
+		desc->handler->enable(irq);
+		/* fall-through */
+	}
+	default:
+		desc->depth--;
+		break;
+	case 0:
+		printk(KERN_ERR "enable_irq(%u) unbalanced from %p\n",
+		       irq, __builtin_return_address(0));
+	}
+	spin_unlock_irqrestore(&desc->lock, flags);
+}
+
+/*
+ * IRQ autodetection code..
+ *
+ * This depends on the fact that any interrupt that
+ * comes in on to an unassigned handler will get stuck
+ * with "IRQ_WAITING" cleared and the interrupt
+ * disabled.
+ */
+
+static DECLARE_MUTEX(probe_sem);
+
+/**
+ *	probe_irq_on	- begin an interrupt autodetect
+ *
+ *	Commence probing for an interrupt. The interrupts are scanned
+ *	and a mask of potential interrupt lines is returned.
+ *
+ */
+unsigned long probe_irq_on(void)
+{
+	unsigned int i;
+	irq_desc_t *desc;
+	unsigned long val;
+	unsigned long delay;
+
+	down(&probe_sem);
+	/* 
+	 * something may have generated an irq long ago and we want to
+	 * flush such a longstanding irq before considering it as spurious. 
+	 */
+	for (i = NR_IRQS - 1; i > 0; i--)  {
+		desc = irq_desc + i;
+
+		spin_lock_irq(&desc->lock);
+		if (!irq_desc[i].action) 
+			irq_desc[i].handler->startup(i);
+		spin_unlock_irq(&desc->lock);
+	}
+
+	/* Wait for longstanding interrupts to trigger. */
+	for (delay = jiffies + HZ/50; time_after(delay, jiffies); )
+		/* about 20ms delay */ barrier();
+
+	/*
+	 * enable any unassigned irqs
+	 * (we must startup again here because if a longstanding irq
+	 * happened in the previous stage, it may have masked itself)
+	 */
+	for (i = NR_IRQS-1; i > 0; i--) {
+		desc = irq_desc + i;
+
+		spin_lock_irq(&desc->lock);
+		if (!desc->action) {
+			desc->status |= IRQ_AUTODETECT | IRQ_WAITING;
+			if (desc->handler->startup(i))
+				desc->status |= IRQ_PENDING;
+		}
+		spin_unlock_irq(&desc->lock);
+	}
+
+	/*
+	 * Wait for spurious interrupts to trigger
+	 */
+	for (delay = jiffies + HZ/10; time_after(delay, jiffies); )
+		/* about 100ms delay */ barrier();
+
+	/*
+	 * Now filter out any obviously spurious interrupts
+	 */
+	val = 0;
+	for (i = 0; i < NR_IRQS; i++) {
+		irq_desc_t *desc = irq_desc + i;
+		unsigned int status;
+
+		spin_lock_irq(&desc->lock);
+		status = desc->status;
+
+		if (status & IRQ_AUTODETECT) {
+			/* It triggered already - consider it spurious. */
+			if (!(status & IRQ_WAITING)) {
+				desc->status = status & ~IRQ_AUTODETECT;
+				desc->handler->shutdown(i);
+			} else
+				if (i < 32)
+					val |= 1 << i;
+		}
+		spin_unlock_irq(&desc->lock);
+	}
+
+	return val;
+}
+
+/**
+ *	probe_irq_mask - scan a bitmap of interrupt lines
+ *	@val:	mask of interrupts to consider
+ *
+ *	Scan the ISA bus interrupt lines and return a bitmap of
+ *	active interrupts. The interrupt probe logic state is then
+ *	returned to its previous value. This function can handle only 
+ *	legacy ISA interrupts
+ *
+ *	Note: we need to scan all the irq's even though we will
+ *	only return ISA irq numbers - just so that we reset them
+ *	all to a known state.
+ */
+unsigned int probe_irq_mask(unsigned long val)
+{
+	int i;
+	unsigned int mask;
+
+	mask = 0;
+	for (i = 0; i < NR_IRQS; i++) {
+		irq_desc_t *desc = irq_desc + i;
+		unsigned int status;
+
+		spin_lock_irq(&desc->lock);
+		status = desc->status;
+
+		if (status & IRQ_AUTODETECT) {
+			if (i < 16 && !(status & IRQ_WAITING))
+				mask |= 1 << i;
+
+			desc->status = status & ~IRQ_AUTODETECT;
+			desc->handler->shutdown(i);
+		}
+		spin_unlock_irq(&desc->lock);
+	}
+	up(&probe_sem);
+
+	return mask & val;
+}
+
+/**
+ *	probe_irq_off	- end an interrupt autodetect
+ *	@val: mask of potential interrupts (unused)
+ *
+ *	Scans the unused interrupt lines and returns the line which
+ *	appears to have triggered the interrupt. If no interrupt was
+ *	found then zero is returned. If more than one interrupt is
+ *	found then minus the first candidate is returned to indicate
+ *	their is doubt. This function can handle any interrupt source.
+ *
+ *	The interrupt probe logic state is returned to its previous
+ *	value.
+ *
+ *	BUGS: When used in a module (which arguably shouldnt happen)
+ *	nothing prevents two IRQ probe callers from overlapping. The
+ *	results of this are non-optimal.
+ */
+int probe_irq_off(unsigned long val)
+{
+	int i, irq_found, nr_irqs;
+
+	nr_irqs = 0;
+	irq_found = 0;
+	for (i = 0; i < NR_IRQS; i++) {
+		irq_desc_t *desc = irq_desc + i;
+		unsigned int status;
+
+		spin_lock_irq(&desc->lock);
+		status = desc->status;
+
+		if (status & IRQ_AUTODETECT) {
+			if (!(status & IRQ_WAITING)) {
+				if (!nr_irqs)
+					irq_found = i;
+				nr_irqs++;
+			}
+			desc->status = status & ~IRQ_AUTODETECT;
+			desc->handler->shutdown(i);
+		}
+		spin_unlock_irq(&desc->lock);
+	}
+	up(&probe_sem);
+
+	if (nr_irqs > 1)
+		irq_found = -irq_found;
+	return irq_found;
+}