ALSA: rawmidi: Add framing mode
This commit adds a new framing mode that frames all MIDI data into 32-byte frames with a timestamp. The main benefit is that we can get accurate timestamps even if userspace wakeup and processing is not immediate. Testing on a Celeron N3150 with this mode has a max jitter of 2.8 ms, compared to the in-kernel seq implementation which has a max jitter of 5 ms during idle and much worse when running scheduler stress tests in parallel. Signed-off-by: David Henningsson <coding@diwic.se> Reviewed-by: Jaroslav Kysela <perex@perex.cz> Link: https://lore.kernel.org/r/20210515071533.55332-1-coding@diwic.se Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
David Henningsson
Takashi Iwai
Родитель
bac5905454
Коммит
08fdced60c
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@ -81,6 +81,8 @@ struct snd_rawmidi_substream {
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bool opened; /* open flag */
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bool append; /* append flag (merge more streams) */
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bool active_sensing; /* send active sensing when close */
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unsigned int framing; /* whether to frame input data */
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unsigned int clock_type; /* clock source to use for input framing */
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int use_count; /* use counter (for output) */
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size_t bytes;
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struct snd_rawmidi *rmidi;
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@ -710,7 +710,7 @@ enum {
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* Raw MIDI section - /dev/snd/midi??
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*/
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#define SNDRV_RAWMIDI_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 1)
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#define SNDRV_RAWMIDI_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 2)
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enum {
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SNDRV_RAWMIDI_STREAM_OUTPUT = 0,
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@ -736,12 +736,38 @@ struct snd_rawmidi_info {
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unsigned char reserved[64]; /* reserved for future use */
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};
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#define SNDRV_RAWMIDI_MODE_FRAMING_MASK (7<<0)
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#define SNDRV_RAWMIDI_MODE_FRAMING_SHIFT 0
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#define SNDRV_RAWMIDI_MODE_FRAMING_NONE (0<<0)
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#define SNDRV_RAWMIDI_MODE_FRAMING_TSTAMP (1<<0)
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#define SNDRV_RAWMIDI_MODE_CLOCK_MASK (7<<3)
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#define SNDRV_RAWMIDI_MODE_CLOCK_SHIFT 3
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#define SNDRV_RAWMIDI_MODE_CLOCK_NONE (0<<3)
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#define SNDRV_RAWMIDI_MODE_CLOCK_REALTIME (1<<3)
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#define SNDRV_RAWMIDI_MODE_CLOCK_MONOTONIC (2<<3)
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#define SNDRV_RAWMIDI_MODE_CLOCK_MONOTONIC_RAW (3<<3)
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#define SNDRV_RAWMIDI_FRAMING_DATA_LENGTH 16
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struct snd_rawmidi_framing_tstamp {
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/* For now, frame_type is always 0. Midi 2.0 is expected to add new
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* types here. Applications are expected to skip unknown frame types.
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*/
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__u8 frame_type;
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__u8 length; /* number of valid bytes in data field */
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__u8 reserved[2];
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__u32 tv_nsec; /* nanoseconds */
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__u64 tv_sec; /* seconds */
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__u8 data[SNDRV_RAWMIDI_FRAMING_DATA_LENGTH];
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} __packed;
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struct snd_rawmidi_params {
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int stream;
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size_t buffer_size; /* queue size in bytes */
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size_t avail_min; /* minimum avail bytes for wakeup */
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unsigned int no_active_sensing: 1; /* do not send active sensing byte in close() */
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unsigned char reserved[16]; /* reserved for future use */
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unsigned int mode; /* For input data only, frame incoming data */
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unsigned char reserved[12]; /* reserved for future use */
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};
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#ifndef __KERNEL__
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@ -680,9 +680,12 @@ static int resize_runtime_buffer(struct snd_rawmidi_runtime *runtime,
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bool is_input)
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{
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char *newbuf, *oldbuf;
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unsigned int framing = params->mode & SNDRV_RAWMIDI_MODE_FRAMING_MASK;
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if (params->buffer_size < 32 || params->buffer_size > 1024L * 1024L)
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return -EINVAL;
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if (framing == SNDRV_RAWMIDI_MODE_FRAMING_TSTAMP && (params->buffer_size & 0x1f) != 0)
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return -EINVAL;
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if (params->avail_min < 1 || params->avail_min > params->buffer_size)
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return -EINVAL;
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if (params->buffer_size != runtime->buffer_size) {
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@ -720,8 +723,24 @@ EXPORT_SYMBOL(snd_rawmidi_output_params);
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int snd_rawmidi_input_params(struct snd_rawmidi_substream *substream,
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struct snd_rawmidi_params *params)
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{
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unsigned int framing = params->mode & SNDRV_RAWMIDI_MODE_FRAMING_MASK;
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unsigned int clock_type = params->mode & SNDRV_RAWMIDI_MODE_CLOCK_MASK;
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int err;
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if (framing == SNDRV_RAWMIDI_MODE_FRAMING_NONE && clock_type != SNDRV_RAWMIDI_MODE_CLOCK_NONE)
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return -EINVAL;
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else if (clock_type > SNDRV_RAWMIDI_MODE_CLOCK_MONOTONIC_RAW)
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return -EINVAL;
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if (framing > SNDRV_RAWMIDI_MODE_FRAMING_TSTAMP)
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return -EINVAL;
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snd_rawmidi_drain_input(substream);
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return resize_runtime_buffer(substream->runtime, params, true);
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err = resize_runtime_buffer(substream->runtime, params, true);
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if (err < 0)
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return err;
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substream->framing = framing;
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substream->clock_type = clock_type;
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return 0;
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}
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EXPORT_SYMBOL(snd_rawmidi_input_params);
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@ -963,6 +982,62 @@ static int snd_rawmidi_control_ioctl(struct snd_card *card,
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return -ENOIOCTLCMD;
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}
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static int receive_with_tstamp_framing(struct snd_rawmidi_substream *substream,
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const unsigned char *buffer, int src_count, const struct timespec64 *tstamp)
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{
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struct snd_rawmidi_runtime *runtime = substream->runtime;
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struct snd_rawmidi_framing_tstamp *dest_ptr;
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struct snd_rawmidi_framing_tstamp frame = { .tv_sec = tstamp->tv_sec, .tv_nsec = tstamp->tv_nsec };
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int dest_frames = 0;
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int orig_count = src_count;
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int frame_size = sizeof(struct snd_rawmidi_framing_tstamp);
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BUILD_BUG_ON(frame_size != 0x20);
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if (snd_BUG_ON((runtime->hw_ptr & 0x1f) != 0))
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return -EINVAL;
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while (src_count > 0) {
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if ((int)(runtime->buffer_size - runtime->avail) < frame_size) {
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runtime->xruns += src_count;
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break;
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}
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if (src_count >= SNDRV_RAWMIDI_FRAMING_DATA_LENGTH)
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frame.length = SNDRV_RAWMIDI_FRAMING_DATA_LENGTH;
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else {
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frame.length = src_count;
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memset(frame.data, 0, SNDRV_RAWMIDI_FRAMING_DATA_LENGTH);
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}
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memcpy(frame.data, buffer, frame.length);
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buffer += frame.length;
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src_count -= frame.length;
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dest_ptr = (struct snd_rawmidi_framing_tstamp *) (runtime->buffer + runtime->hw_ptr);
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*dest_ptr = frame;
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runtime->avail += frame_size;
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runtime->hw_ptr += frame_size;
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runtime->hw_ptr %= runtime->buffer_size;
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dest_frames++;
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}
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return orig_count - src_count;
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}
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static struct timespec64 get_framing_tstamp(struct snd_rawmidi_substream *substream)
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{
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struct timespec64 ts64 = {0, 0};
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switch (substream->clock_type) {
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case SNDRV_RAWMIDI_MODE_CLOCK_MONOTONIC_RAW:
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ktime_get_raw_ts64(&ts64);
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break;
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case SNDRV_RAWMIDI_MODE_CLOCK_MONOTONIC:
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ktime_get_ts64(&ts64);
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break;
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case SNDRV_RAWMIDI_MODE_CLOCK_REALTIME:
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ktime_get_real_ts64(&ts64);
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break;
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}
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return ts64;
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}
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/**
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* snd_rawmidi_receive - receive the input data from the device
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* @substream: the rawmidi substream
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@ -977,6 +1052,7 @@ int snd_rawmidi_receive(struct snd_rawmidi_substream *substream,
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const unsigned char *buffer, int count)
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{
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unsigned long flags;
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struct timespec64 ts64 = get_framing_tstamp(substream);
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int result = 0, count1;
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struct snd_rawmidi_runtime *runtime = substream->runtime;
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@ -987,8 +1063,11 @@ int snd_rawmidi_receive(struct snd_rawmidi_substream *substream,
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"snd_rawmidi_receive: input is not active!!!\n");
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return -EINVAL;
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}
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spin_lock_irqsave(&runtime->lock, flags);
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if (count == 1) { /* special case, faster code */
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if (substream->framing == SNDRV_RAWMIDI_MODE_FRAMING_TSTAMP) {
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result = receive_with_tstamp_framing(substream, buffer, count, &ts64);
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} else if (count == 1) { /* special case, faster code */
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substream->bytes++;
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if (runtime->avail < runtime->buffer_size) {
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runtime->buffer[runtime->hw_ptr++] = buffer[0];
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@ -1541,6 +1620,8 @@ static void snd_rawmidi_proc_info_read(struct snd_info_entry *entry,
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struct snd_rawmidi_substream *substream;
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struct snd_rawmidi_runtime *runtime;
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unsigned long buffer_size, avail, xruns;
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unsigned int clock_type;
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static const char *clock_names[4] = { "none", "realtime", "monotonic", "monotonic raw" };
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rmidi = entry->private_data;
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snd_iprintf(buffer, "%s\n\n", rmidi->name);
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@ -1596,6 +1677,14 @@ static void snd_rawmidi_proc_info_read(struct snd_info_entry *entry,
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" Avail : %lu\n"
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" Overruns : %lu\n",
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buffer_size, avail, xruns);
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if (substream->framing == SNDRV_RAWMIDI_MODE_FRAMING_TSTAMP) {
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clock_type = substream->clock_type >> SNDRV_RAWMIDI_MODE_CLOCK_SHIFT;
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if (!snd_BUG_ON(clock_type >= sizeof(clock_names)))
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snd_iprintf(buffer,
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" Framing : tstamp\n"
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" Clock type : %s\n",
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clock_names[clock_type]);
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}
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}
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}
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}
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@ -13,7 +13,8 @@ struct snd_rawmidi_params32 {
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u32 buffer_size;
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u32 avail_min;
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unsigned int no_active_sensing; /* avoid bit-field */
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unsigned char reserved[16];
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unsigned int mode;
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unsigned char reserved[12];
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} __attribute__((packed));
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static int snd_rawmidi_ioctl_params_compat(struct snd_rawmidi_file *rfile,
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@ -25,6 +26,7 @@ static int snd_rawmidi_ioctl_params_compat(struct snd_rawmidi_file *rfile,
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if (get_user(params.stream, &src->stream) ||
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get_user(params.buffer_size, &src->buffer_size) ||
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get_user(params.avail_min, &src->avail_min) ||
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get_user(params.mode, &src->mode) ||
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get_user(val, &src->no_active_sensing))
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return -EFAULT;
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params.no_active_sensing = val;
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