This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / arch / i386 / kernel / hpet.c

diff --git a/arch/i386/kernel/hpet.c b/arch/i386/kernel/hpet.c
new file mode 100644 (file)
index 0000000..17647a5
--- /dev/null
+++ b/arch/i386/kernel/hpet.c
@@ -0,0 +1,67 @@
+#include <linux/clocksource.h>
+#include <linux/errno.h>
+#include <linux/hpet.h>
+#include <linux/init.h>
+
+#include <asm/hpet.h>
+#include <asm/io.h>
+
+#define HPET_MASK      CLOCKSOURCE_MASK(32)
+#define HPET_SHIFT     22
+
+/* FSEC = 10^-15 NSEC = 10^-9 */
+#define FSEC_PER_NSEC  1000000
+
+static void *hpet_ptr;
+
+static cycle_t read_hpet(void)
+{
+       return (cycle_t)readl(hpet_ptr);
+}
+
+static struct clocksource clocksource_hpet = {
+       .name           = "hpet",
+       .rating         = 250,
+       .read           = read_hpet,
+       .mask           = HPET_MASK,
+       .mult           = 0, /* set below */
+       .shift          = HPET_SHIFT,
+       .is_continuous  = 1,
+};
+
+static int __init init_hpet_clocksource(void)
+{
+       unsigned long hpet_period;
+       void __iomem* hpet_base;
+       u64 tmp;
+
+       if (!is_hpet_enabled())
+               return -ENODEV;
+
+       /* calculate the hpet address: */
+       hpet_base =
+               (void __iomem*)ioremap_nocache(hpet_address, HPET_MMAP_SIZE);
+       hpet_ptr = hpet_base + HPET_COUNTER;
+
+       /* calculate the frequency: */
+       hpet_period = readl(hpet_base + HPET_PERIOD);
+
+       /*
+        * hpet period is in femto seconds per cycle
+        * so we need to convert this to ns/cyc units
+        * aproximated by mult/2^shift
+        *
+        *  fsec/cyc * 1nsec/1000000fsec = nsec/cyc = mult/2^shift
+        *  fsec/cyc * 1ns/1000000fsec * 2^shift = mult
+        *  fsec/cyc * 2^shift * 1nsec/1000000fsec = mult
+        *  (fsec/cyc << shift)/1000000 = mult
+        *  (hpet_period << shift)/FSEC_PER_NSEC = mult
+        */
+       tmp = (u64)hpet_period << HPET_SHIFT;
+       do_div(tmp, FSEC_PER_NSEC);
+       clocksource_hpet.mult = (u32)tmp;
+
+       return clocksource_register(&clocksource_hpet);
+}
+
+module_init(init_hpet_clocksource);