1 files changed, 37 insertions, 15 deletions

diff --git a/arch/x86/kernel/mfgpt_32.c b/arch/x86/kernel/mfgpt_32.c
index 07c0f828f488..3b599518c322 100644
--- a/arch/x86/kernel/mfgpt_32.c
+++ b/arch/x86/kernel/mfgpt_32.c
@@ -33,6 +33,8 @@
 #include <linux/module.h>
 #include <asm/geode.h>
 
+#define MFGPT_DEFAULT_IRQ	7
+
 static struct mfgpt_timer_t {
 	unsigned int avail:1;
 } mfgpt_timers[MFGPT_MAX_TIMERS];
@@ -157,29 +159,48 @@ int geode_mfgpt_toggle_event(int timer, int cmp, int event, int enable)
 }
 EXPORT_SYMBOL_GPL(geode_mfgpt_toggle_event);
 
-int geode_mfgpt_set_irq(int timer, int cmp, int irq, int enable)
+int geode_mfgpt_set_irq(int timer, int cmp, int *irq, int enable)
 {
-	u32 val, dummy;
-	int offset;
+	u32 zsel, lpc, dummy;
+	int shift;
 
 	if (timer < 0 || timer >= MFGPT_MAX_TIMERS)
 		return -EIO;
 
-	if (geode_mfgpt_toggle_event(timer, cmp, MFGPT_EVENT_IRQ, enable))
+	/*
+	 * Unfortunately, MFGPTs come in pairs sharing their IRQ lines. If VSA
+	 * is using the same CMP of the timer's Siamese twin, the IRQ is set to
+	 * 2, and we mustn't use nor change it.
+	 * XXX: Likewise, 2 Linux drivers might clash if the 2nd overwrites the
+	 * IRQ of the 1st. This can only happen if forcing an IRQ, calling this
+	 * with *irq==0 is safe. Currently there _are_ no 2 drivers.
+	 */
+	rdmsr(MSR_PIC_ZSEL_LOW, zsel, dummy);
+	shift = ((cmp == MFGPT_CMP1 ? 0 : 4) + timer % 4) * 4;
+	if (((zsel >> shift) & 0xF) == 2)
 		return -EIO;
 
-	rdmsr(MSR_PIC_ZSEL_LOW, val, dummy);
+	/* Choose IRQ: if none supplied, keep IRQ already set or use default */
+	if (!*irq)
+		*irq = (zsel >> shift) & 0xF;
+	if (!*irq)
+		*irq = MFGPT_DEFAULT_IRQ;
 
-	offset = (timer % 4) * 4;
-
-	val &= ~((0xF << offset) | (0xF << (offset + 16)));
+	/* Can't use IRQ if it's 0 (=disabled), 2, or routed to LPC */
+	if (*irq < 1 || *irq == 2 || *irq > 15)
+		return -EIO;
+	rdmsr(MSR_PIC_IRQM_LPC, lpc, dummy);
+	if (lpc & (1 << *irq))
+		return -EIO;
 
+	/* All chosen and checked - go for it */
+	if (geode_mfgpt_toggle_event(timer, cmp, MFGPT_EVENT_IRQ, enable))
+		return -EIO;
 	if (enable) {
-		val |= (irq & 0x0F) << (offset);
-		val |= (irq & 0x0F) << (offset + 16);
+		zsel = (zsel & ~(0xF << shift)) | (*irq << shift);
+		wrmsr(MSR_PIC_ZSEL_LOW, zsel, dummy);
 	}
 
-	wrmsr(MSR_PIC_ZSEL_LOW, val, dummy);
 	return 0;
 }
 
@@ -242,7 +263,7 @@ EXPORT_SYMBOL_GPL(geode_mfgpt_alloc_timer);
 static unsigned int mfgpt_tick_mode = CLOCK_EVT_MODE_SHUTDOWN;
 static u16 mfgpt_event_clock;
 
-static int irq = 7;
+static int irq;
 static int __init mfgpt_setup(char *str)
 {
 	get_option(&str, &irq);
@@ -346,7 +367,7 @@ int __init mfgpt_timer_setup(void)
 	mfgpt_event_clock = timer;
 
 	/* Set up the IRQ on the MFGPT side */
-	if (geode_mfgpt_setup_irq(mfgpt_event_clock, MFGPT_CMP2, irq)) {
+	if (geode_mfgpt_setup_irq(mfgpt_event_clock, MFGPT_CMP2, &irq)) {
 		printk(KERN_ERR "mfgpt-timer:  Could not set up IRQ %d\n", irq);
 		return -EIO;
 	}
@@ -374,13 +395,14 @@ int __init mfgpt_timer_setup(void)
 			&mfgpt_clockevent);
 
 	printk(KERN_INFO
-	       "mfgpt-timer:  registering the MFGPT timer as a clock event.\n");
+	       "mfgpt-timer:  Registering MFGPT timer %d as a clock event, using IRQ %d\n",
+	       timer, irq);
 	clockevents_register_device(&mfgpt_clockevent);
 
 	return 0;
 
 err:
-	geode_mfgpt_release_irq(mfgpt_event_clock, MFGPT_CMP2, irq);
+	geode_mfgpt_release_irq(mfgpt_event_clock, MFGPT_CMP2, &irq);
 	printk(KERN_ERR
 	       "mfgpt-timer:  Unable to set up the MFGPT clock source\n");
 	return -EIO;