hpet: /dev/hpet - fixes and cleanup

Minor /dev/hpet updates and bugfixes:

  * Remove dead code, mostly remnants of an incomplete/unusable
    kernel interface ... noted when addressing "sparse" warnings:
      + hpet_unregister() and a routine it calls
      + hpet_task and all references, including hpet_task_lock
      + hpet_data.hd_flags (and HPET_DATA_PLATFORM)

  * Correct and improve boot message:
      + displays *counter* (shared between comparators) bit width,
        not *timer* bit widths (which are often mixed)
      + relabel "timers" as "comparators"; this is less confusing,
        they are not independent like normal timers are (sigh)
      + display MHz not Hz; it's never less than 10 MHz.

  * Tighten and correct the userspace interface code
      + don't accidentally program comparators in 64-bit mode using
        32-bit values ... always force comparators into 32-bit mode
      + provide the correct bit definition flagging comparators with
        periodic capability ... the ABI is unchanged

  * Update Documentation/hpet.txt
      + be more correct and current
      + expand description a bit
      + don't mention that now-gone kernel interface

Plus, add a FIXME comment for something that could cause big trouble
on systems with more capable HPETs than at least Intel seems to ship.

It seems that few folk use this userspace interface; it's not very
usable given the general lack of HPET IRQ routing.  I'm told that
the only real point of it any more is to mmap for fast timestamps;
IMO that's handled better through the gettimeofday() vsyscall.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 24 insertions, 66 deletions

diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c
index f3981ffe20f0..4bc1da4d4f80 100644
--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -53,6 +53,11 @@
 
 #define HPET_RANGE_SIZE         1024    /* from HPET spec */
 
+
+/* WARNING -- don't get confused.  These macros are never used
+ * to write the (single) counter, and rarely to read it.
+ * They're badly named; to fix, someday.
+ */
 #if BITS_PER_LONG == 64
 #define write_counter(V, MC)    writeq(V, MC)
 #define read_counter(MC)        readq(MC)
@@ -77,7 +82,7 @@ static struct clocksource clocksource_hpet = {
         .rating         = 250,
         .read           = read_hpet,
         .mask           = CLOCKSOURCE_MASK(64),
-        .mult           = 0, /*to be caluclated*/
+        .mult           = 0, /* to be calculated */
         .shift          = 10,
         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 };
@@ -86,8 +91,6 @@ static struct clocksource *hpet_clocksource;
 
 /* A lock for concurrent access by app and isr hpet activity. */
 static DEFINE_SPINLOCK(hpet_lock);
-/* A lock for concurrent intermodule access to hpet and isr hpet activity. */
-static DEFINE_SPINLOCK(hpet_task_lock);
 
 #define HPET_DEV_NAME   (7)
 
@@ -99,7 +102,6 @@ struct hpet_dev {
         unsigned long hd_irqdata;
         wait_queue_head_t hd_waitqueue;
         struct fasync_struct *hd_async_queue;
-        struct hpet_task *hd_task;
         unsigned int hd_flags;
         unsigned int hd_irq;
         unsigned int hd_hdwirq;
@@ -173,11 +175,6 @@ static irqreturn_t hpet_interrupt(int irq, void *data)
                 writel(isr, &devp->hd_hpet->hpet_isr);
         spin_unlock(&hpet_lock);
 
-        spin_lock(&hpet_task_lock);
-        if (devp->hd_task)
-                devp->hd_task->ht_func(devp->hd_task->ht_data);
-        spin_unlock(&hpet_task_lock);
-
         wake_up_interruptible(&devp->hd_waitqueue);
 
         kill_fasync(&devp->hd_async_queue, SIGIO, POLL_IN);
@@ -260,8 +257,7 @@ static int hpet_open(struct inode *inode, struct file *file)
 
         for (devp = NULL, hpetp = hpets; hpetp && !devp; hpetp = hpetp->hp_next)
                 for (i = 0; i < hpetp->hp_ntimer; i++)
-                        if (hpetp->hp_dev[i].hd_flags & HPET_OPEN
-                            || hpetp->hp_dev[i].hd_task)
+                        if (hpetp->hp_dev[i].hd_flags & HPET_OPEN)
                                 continue;
                         else {
                                 devp = &hpetp->hp_dev[i];
@@ -504,7 +500,11 @@ static int hpet_ioctl_ieon(struct hpet_dev *devp)
         devp->hd_irq = irq;
         t = devp->hd_ireqfreq;
         v = readq(&timer->hpet_config);
-        g = v | Tn_INT_ENB_CNF_MASK;
+
+        /* 64-bit comparators are not yet supported through the ioctls,
+         * so force this into 32-bit mode if it supports both modes
+         */
+        g = v | Tn_32MODE_CNF_MASK | Tn_INT_ENB_CNF_MASK;
 
         if (devp->hd_flags & HPET_PERIODIC) {
                 write_counter(t, &timer->hpet_compare);
@@ -514,6 +514,12 @@ static int hpet_ioctl_ieon(struct hpet_dev *devp)
                 v |= Tn_VAL_SET_CNF_MASK;
                 writeq(v, &timer->hpet_config);
                 local_irq_save(flags);
+
+                /* NOTE:  what we modify here is a hidden accumulator
+                 * register supported by periodic-capable comparators.
+                 * We never want to modify the (single) counter; that
+                 * would affect all the comparators.
+                 */
                 m = read_counter(&hpet->hpet_mc);
                 write_counter(t + m + hpetp->hp_delta, &timer->hpet_compare);
         } else {
@@ -667,57 +673,6 @@ static int hpet_is_known(struct hpet_data *hdp)
         return 0;
 }
 
-static inline int hpet_tpcheck(struct hpet_task *tp)
-{
-        struct hpet_dev *devp;
-        struct hpets *hpetp;
-
-        devp = tp->ht_opaque;
-
-        if (!devp)
-                return -ENXIO;
-
-        for (hpetp = hpets; hpetp; hpetp = hpetp->hp_next)
-                if (devp >= hpetp->hp_dev
-                    && devp < (hpetp->hp_dev + hpetp->hp_ntimer)
-                    && devp->hd_hpet == hpetp->hp_hpet)
-                        return 0;
-
-        return -ENXIO;
-}
-
-#if 0
-int hpet_unregister(struct hpet_task *tp)
-{
-        struct hpet_dev *devp;
-        struct hpet_timer __iomem *timer;
-        int err;
-
-        if ((err = hpet_tpcheck(tp)))
-                return err;
-
-        spin_lock_irq(&hpet_task_lock);
-        spin_lock(&hpet_lock);
-
-        devp = tp->ht_opaque;
-        if (devp->hd_task != tp) {
-                spin_unlock(&hpet_lock);
-                spin_unlock_irq(&hpet_task_lock);
-                return -ENXIO;
-        }
-
-        timer = devp->hd_timer;
-        writeq((readq(&timer->hpet_config) & ~Tn_INT_ENB_CNF_MASK),
-               &timer->hpet_config);
-        devp->hd_flags &= ~(HPET_IE | HPET_PERIODIC);
-        devp->hd_task = NULL;
-        spin_unlock(&hpet_lock);
-        spin_unlock_irq(&hpet_task_lock);
-
-        return 0;
-}
-#endif  /*  0  */
-
 static ctl_table hpet_table[] = {
         {
          .ctl_name = CTL_UNNUMBERED,
@@ -872,9 +827,12 @@ int hpet_alloc(struct hpet_data *hdp)
                 printk("%s %d", i > 0 ? "," : "", hdp->hd_irq[i]);
         printk("\n");
 
-        printk(KERN_INFO "hpet%u: %u %d-bit timers, %Lu Hz\n",
-               hpetp->hp_which, hpetp->hp_ntimer,
-               cap & HPET_COUNTER_SIZE_MASK ? 64 : 32, hpetp->hp_tick_freq);
+        printk(KERN_INFO
+                "hpet%u: %u comparators, %d-bit %u.%06u MHz counter\n",
+                hpetp->hp_which, hpetp->hp_ntimer,
+                cap & HPET_COUNTER_SIZE_MASK ? 64 : 32,
+                (unsigned) (hpetp->hp_tick_freq / 1000000),
+                (unsigned) (hpetp->hp_tick_freq % 1000000));
 
         mcfg = readq(&hpet->hpet_config);
         if ((mcfg & HPET_ENABLE_CNF_MASK) == 0) {