ALSA: Add hrtimer backend for ALSA timer interface

Added the hrtimer backend for ALSA timer interface.
It can be used for the sequencer timer source.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 140 insertions, 0 deletions

diff --git a/sound/core/hrtimer.c b/sound/core/hrtimer.c
new file mode 100644
index 000000000000..b712d7f211ff
--- /dev/null
+++ b/sound/core/hrtimer.c
@@ -0,0 +1,140 @@
+/*
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/hrtimer.h>
+#include <sound/core.h>
+#include <sound/timer.h>
+
+MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
+MODULE_DESCRIPTION("ALSA hrtimer backend");
+MODULE_LICENSE("GPL");
+
+MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
+
+#define NANO_SEC        1000000000UL    /* 10^9 in sec */
+static unsigned int resolution;
+
+struct snd_hrtimer {
+        struct snd_timer *timer;
+        struct hrtimer hrt;
+};
+
+static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
+{
+        struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
+        struct snd_timer *t = stime->timer;
+        hrtimer_forward_now(hrt, ktime_set(0, t->sticks * resolution));
+        snd_timer_interrupt(stime->timer, t->sticks);
+        return HRTIMER_RESTART;
+}
+
+static int snd_hrtimer_open(struct snd_timer *t)
+{
+        struct snd_hrtimer *stime;
+
+        stime = kmalloc(sizeof(*stime), GFP_KERNEL);
+        if (!stime)
+                return -ENOMEM;
+        hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+        stime->timer = t;
+        stime->hrt.cb_mode = HRTIMER_CB_SOFTIRQ;
+        stime->hrt.function = snd_hrtimer_callback;
+        t->private_data = stime;
+        return 0;
+}
+
+static int snd_hrtimer_close(struct snd_timer *t)
+{
+        struct snd_hrtimer *stime = t->private_data;
+
+        if (stime) {
+                hrtimer_cancel(&stime->hrt);
+                kfree(stime);
+                t->private_data = NULL;
+        }
+        return 0;
+}
+
+static int snd_hrtimer_start(struct snd_timer *t)
+{
+        struct snd_hrtimer *stime = t->private_data;
+
+        hrtimer_start(&stime->hrt, ktime_set(0, t->sticks * resolution),
+                      HRTIMER_MODE_REL);
+        return 0;
+}
+
+static int snd_hrtimer_stop(struct snd_timer *t)
+{
+        struct snd_hrtimer *stime = t->private_data;
+
+        hrtimer_cancel(&stime->hrt);
+        return 0;
+}
+
+static struct snd_timer_hardware hrtimer_hw = {
+        .flags =        (SNDRV_TIMER_HW_AUTO |
+                         /*SNDRV_TIMER_HW_FIRST |*/
+                         SNDRV_TIMER_HW_TASKLET),
+        .open =         snd_hrtimer_open,
+        .close =        snd_hrtimer_close,
+        .start =        snd_hrtimer_start,
+        .stop =         snd_hrtimer_stop,
+};
+
+/*
+ * entry functions
+ */
+
+static struct snd_timer *mytimer;
+
+static int __init snd_hrtimer_init(void)
+{
+        struct snd_timer *timer;
+        struct timespec tp;
+        int err;
+
+        hrtimer_get_res(CLOCK_MONOTONIC, &tp);
+        if (tp.tv_sec > 0 || !tp.tv_nsec) {
+                snd_printk(KERN_ERR
+                           "snd-hrtimer: Invalid resolution %u.%09u",
+                           (unsigned)tp.tv_sec, (unsigned)tp.tv_nsec);
+                return -EINVAL;
+        }
+        resolution = tp.tv_nsec;
+
+        /* Create a new timer and set up the fields */
+        err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER,
+                                   &timer);
+        if (err < 0)
+                return err;
+
+        timer->module = THIS_MODULE;
+        strcpy(timer->name, "HR timer");
+        timer->hw = hrtimer_hw;
+        timer->hw.resolution = resolution;
+        timer->hw.ticks = NANO_SEC / resolution;
+
+        err = snd_timer_global_register(timer);
+        if (err < 0) {
+                snd_timer_global_free(timer);
+                return err;
+        }
+        mytimer = timer; /* remember this */
+
+        return 0;
+}
+
+static void __exit snd_hrtimer_exit(void)
+{
+        if (mytimer) {
+                snd_timer_global_free(mytimer);
+                mytimer = NULL;
+        }
+}
+
+module_init(snd_hrtimer_init);
+module_exit(snd_hrtimer_exit);