x86: assign IRQs to HPET timers

The userspace API for the HPET (see Documentation/hpet.txt) did not work. The
HPET_IE_ON ioctl was failing as there was no IRQ assigned to the timer
device. This patch fixes it by allocating IRQs to timer blocks in the HPET.

arch/x86/kernel/hpet.c |   13 +++++--------
drivers/char/hpet.c    |   45 ++++++++++++++++++++++++++++++++++++++-------
include/linux/hpet.h   |    2 +-
3 files changed, 44 insertions(+), 16 deletions(-)

Signed-off-by: Balaji Rao <balajirrao@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/char/hpet.c

@@ -806,14 +806,14 @@ static unsigned long hpet_calibrate(struct hpets *hpetp)
 
 int hpet_alloc(struct hpet_data *hdp)
 {
-	u64 cap, mcfg;
+	u64 cap, mcfg, hpet_config;
 	struct hpet_dev *devp;
-	u32 i, ntimer;
+	u32 i, ntimer, irq;
 	struct hpets *hpetp;
 	size_t siz;
 	struct hpet __iomem *hpet;
 	static struct hpets *last = NULL;
-	unsigned long period;
+	unsigned long period, irq_bitmap;
 	unsigned long long temp;
 
 	/*
@@ -840,12 +840,42 @@ int hpet_alloc(struct hpet_data *hdp)
 	hpetp->hp_hpet_phys = hdp->hd_phys_address;
 
 	hpetp->hp_ntimer = hdp->hd_nirqs;
-
-	for (i = 0; i < hdp->hd_nirqs; i++)
-		hpetp->hp_dev[i].hd_hdwirq = hdp->hd_irq[i];
-
 	hpet = hpetp->hp_hpet;
 
+	/* Assign IRQs statically for legacy devices */
+	hpetp->hp_dev[0].hd_hdwirq = hdp->hd_irq[0];
+	hpetp->hp_dev[1].hd_hdwirq = hdp->hd_irq[1];
+
+	/* Assign IRQs dynamically for the others */
+	for (i = 2, devp = &hpetp->hp_dev[2]; i < hdp->hd_nirqs; i++, devp++) {
+		struct hpet_timer __iomem *timer;
+
+		timer = &hpet->hpet_timers[devp - hpetp->hp_dev];
+
+		hpet_config = readq(&timer->hpet_config);
+		irq_bitmap = (hpet_config & Tn_INT_ROUTE_CAP_MASK)
+			>> Tn_INT_ROUTE_CAP_SHIFT;
+		if (!irq_bitmap)
+			irq = 0;        /* No valid IRQ Assignable */
+		else {
+			irq = find_first_bit(&irq_bitmap, 32);
+			do {
+				hpet_config |= irq << Tn_INT_ROUTE_CNF_SHIFT;
+				writeq(hpet_config, &timer->hpet_config);
+
+				/*
+				 * Verify whether we have written a valid
+				 * IRQ number by reading it back again
+				 */
+				hpet_config = readq(&timer->hpet_config);
+				if (irq == (hpet_config & Tn_INT_ROUTE_CNF_MASK)
+						>> Tn_INT_ROUTE_CNF_SHIFT)
+					break;  /* Success */
+			} while ((irq = (find_next_bit(&irq_bitmap, 32, irq))));
+		}
+		hpetp->hp_dev[i].hd_hdwirq = irq;
+	}
+
 	cap = readq(&hpet->hpet_cap);
 
 	ntimer = ((cap & HPET_NUM_TIM_CAP_MASK) >> HPET_NUM_TIM_CAP_SHIFT) + 1;
@@ -875,7 +905,8 @@ int hpet_alloc(struct hpet_data *hdp)
 		hpetp->hp_which, hdp->hd_phys_address,
 		hpetp->hp_ntimer > 1 ? "s" : "");
 	for (i = 0; i < hpetp->hp_ntimer; i++)
-		printk("%s %d", i > 0 ? "," : "", hdp->hd_irq[i]);
+		printk("%s %d", i > 0 ? "," : "",
+				hpetp->hp_dev[i].hd_hdwirq);
 	printk("\n");
 
 	printk(KERN_INFO "hpet%u: %u %d-bit timers, %Lu Hz\n",