[PATCH] hpet: allow shared interrupts

This patch adds support for shared HPET interrupts.

The driver previously acknowledged interrupts for both edge and level
interrupts, but didn't actually allow a shared interrupt in the latter case.

We use a new per-timer flag to save whether the timer's interrupt might be
shared, and use it to do the processing required for level interrupts only if
necessary.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Acked-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 21 insertions, 7 deletions

diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c
index 85d39ff286c4..8e59639fb03c 100644
--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -90,6 +90,7 @@ static struct hpets *hpets;
 #define HPET_OPEN               0x0001
 #define HPET_IE                 0x0002  /* interrupt enabled */
 #define HPET_PERIODIC           0x0004
+#define HPET_SHARED_IRQ         0x0008
 
 #if BITS_PER_LONG == 64
 #define write_counter(V, MC)    writeq(V, MC)
@@ -120,6 +121,11 @@ static irqreturn_t hpet_interrupt(int irq, void *data, struct pt_regs *regs)
         unsigned long isr;
 
         devp = data;
+        isr = 1 << (devp - devp->hd_hpets->hp_dev);
+
+        if ((devp->hd_flags & HPET_SHARED_IRQ) &&
+            !(isr & readl(&devp->hd_hpet->hpet_isr)))
+                return IRQ_NONE;
 
         spin_lock(&hpet_lock);
         devp->hd_irqdata++;
@@ -137,8 +143,8 @@ static irqreturn_t hpet_interrupt(int irq, void *data, struct pt_regs *regs)
                               &devp->hd_timer->hpet_compare);
         }
 
-        isr = (1 << (devp - devp->hd_hpets->hp_dev));
-        writeq(isr, &devp->hd_hpet->hpet_isr);
+        if (devp->hd_flags & HPET_SHARED_IRQ)
+                writel(isr, &devp->hd_hpet->hpet_isr);
         spin_unlock(&hpet_lock);
 
         spin_lock(&hpet_task_lock);
@@ -375,15 +381,21 @@ static int hpet_ioctl_ieon(struct hpet_dev *devp)
         }
 
         devp->hd_flags |= HPET_IE;
+
+        if (readl(&timer->hpet_config) & Tn_INT_TYPE_CNF_MASK)
+                devp->hd_flags |= HPET_SHARED_IRQ;
         spin_unlock_irq(&hpet_lock);
 
         irq = devp->hd_hdwirq;
 
         if (irq) {
-                sprintf(devp->hd_name, "hpet%d", (int)(devp - hpetp->hp_dev));
+                unsigned long irq_flags;
 
-                if (request_irq
-                    (irq, hpet_interrupt, SA_INTERRUPT, devp->hd_name, (void *)devp)) {
+                sprintf(devp->hd_name, "hpet%d", (int)(devp - hpetp->hp_dev));
+                irq_flags = devp->hd_flags & HPET_SHARED_IRQ
+                                                ? SA_SHIRQ : SA_INTERRUPT;
+                if (request_irq(irq, hpet_interrupt, irq_flags,
+                                devp->hd_name, (void *)devp)) {
                         printk(KERN_ERR "hpet: IRQ %d is not free\n", irq);
                         irq = 0;
                 }
@@ -417,8 +429,10 @@ static int hpet_ioctl_ieon(struct hpet_dev *devp)
                 write_counter(t + m + hpetp->hp_delta, &timer->hpet_compare);
         }
 
-        isr = (1 << (devp - hpets->hp_dev));
-        writeq(isr, &hpet->hpet_isr);
+        if (devp->hd_flags & HPET_SHARED_IRQ) {
+                isr = 1 << (devp - hpets->hp_dev);
+                writel(isr, &hpet->hpet_isr);
+        }
         writeq(g, &timer->hpet_config);
         local_irq_restore(flags);