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>

4 files changed, 166 insertions, 1 deletions

diff --git a/sound/core/Kconfig b/sound/core/Kconfig
index 66348c92f88d..406a45010985 100644
--- a/sound/core/Kconfig
+++ b/sound/core/Kconfig
@@ -95,6 +95,26 @@ config SND_SEQUENCER_OSS
           this will be compiled as a module. The module will be called
           snd-seq-oss.
 
+config SND_HRTIMER
+        tristate "HR-timer backend support"
+        depends on HIGH_RES_TIMERS
+        select SND_TIMER
+        help
+          Say Y here to enable HR-timer backend for ALSA timer.  ALSA uses
+          the hrtimer as a precise timing source. The ALSA sequencer code
+          also can use this timing source.
+
+          To compile this driver as a module, choose M here: the module
+          will be called snd-hrtimer.
+
+config SND_SEQ_HRTIMER_DEFAULT
+        bool "Use HR-timer as default sequencer timer"
+        depends on SND_HRTIMER && SND_SEQUENCER
+        default y
+        help
+          Say Y here to use the HR-timer backend as the default sequencer
+          timer.
+
 config SND_RTCTIMER
         tristate "RTC Timer support"
         depends on RTC
@@ -114,6 +134,7 @@ config SND_RTCTIMER
 config SND_SEQ_RTCTIMER_DEFAULT
         bool "Use RTC as default sequencer timer"
         depends on SND_RTCTIMER && SND_SEQUENCER
+        dpeends on !SND_SEQ_HRTIMER_DEFAULT
         default y
         help
           Say Y here to use the RTC timer as the default sequencer
diff --git a/sound/core/Makefile b/sound/core/Makefile
index d57125a5687d..4229052e7b91 100644
--- a/sound/core/Makefile
+++ b/sound/core/Makefile
@@ -17,12 +17,14 @@ snd-page-alloc-$(CONFIG_HAS_DMA) += sgbuf.o
 
 snd-rawmidi-objs  := rawmidi.o
 snd-timer-objs    := timer.o
+snd-hrtimer-objs  := hrtimer.o
 snd-rtctimer-objs := rtctimer.o
 snd-hwdep-objs    := hwdep.o
 
 obj-$(CONFIG_SND)               += snd.o
 obj-$(CONFIG_SND_HWDEP)         += snd-hwdep.o
 obj-$(CONFIG_SND_TIMER)         += snd-timer.o
+obj-$(CONFIG_SND_HRTIMER)       += snd-hrtimer.o
 obj-$(CONFIG_SND_RTCTIMER)      += snd-rtctimer.o
 obj-$(CONFIG_SND_PCM)           += snd-pcm.o snd-page-alloc.o
 obj-$(CONFIG_SND_RAWMIDI)       += snd-rawmidi.o
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);
diff --git a/sound/core/seq/seq.c b/sound/core/seq/seq.c
index ee0f8405ab35..bf09a5ad1865 100644
--- a/sound/core/seq/seq.c
+++ b/sound/core/seq/seq.c
@@ -43,7 +43,9 @@ int seq_default_timer_class = SNDRV_TIMER_CLASS_GLOBAL;
 int seq_default_timer_sclass = SNDRV_TIMER_SCLASS_NONE;
 int seq_default_timer_card = -1;
 int seq_default_timer_device =
-#ifdef CONFIG_SND_SEQ_RTCTIMER_DEFAULT
+#ifdef CONFIG_SND_SEQ_HRTIMER_DEFAULT
+        SNDRV_TIMER_GLOBAL_HRTIMER
+#elif defined(CONFIG_SND_SEQ_RTCTIMER_DEFAULT)
         SNDRV_TIMER_GLOBAL_RTC
 #else
         SNDRV_TIMER_GLOBAL_SYSTEM