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us144mkii
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more up to reverse eng report spec improvements 

Still not happy with latency logic, earlier commits  managed 1.3ms at 48khz while this  can only do 10.7ms. Still  more room for fixing before moving to capture
This commit is contained in:
serifpersia 2025-06-29 19:15:41 +02:00
parent f9475374a7
commit ded6ed5652
2 changed files with 51 additions and 3 deletions
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54
us144mkii.c
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@ -104,20 +104,25 @@ struct tascam_card {
atomic_t playback_active;
int current_rate;
/* --- Feedback Synchronization State --- */
unsigned int feedback_accumulator_pattern[FEEDBACK_ACCUMULATOR_SIZE];
unsigned int feedback_pattern_out_idx;
unsigned int feedback_pattern_in_idx;
bool feedback_synced;
/* --- Playback Position Tracking --- */
snd_pcm_uframes_t driver_playback_pos;
u64 playback_frames_consumed;
u64 last_period_pos;
/* --- Rate-Specific Data --- */
const unsigned int (*feedback_patterns)[8];
unsigned int feedback_base_value;
unsigned int feedback_max_value;
unsigned int feedback_urb_skip_count;
};
/* Pre-calculated patterns for frames-per-microframe based on feedback value. */
static const unsigned int latency_profile_packets[] = { 5, 1, 2, 5, 5 };
static const unsigned int patterns_48khz[5][8] = {
{5, 6, 6, 6, 5, 6, 6, 6}, {5, 6, 6, 6, 6, 6, 6, 6},
@ -464,13 +469,18 @@ static int tascam_pcm_prepare(struct snd_pcm_substream *substream)
size_t nominal_bytes_per_packet;
size_t total_bytes_in_urb;
/* Reset all playback and sync state variables. */
tascam->driver_playback_pos = 0;
tascam->playback_frames_consumed = 0;
tascam->last_period_pos = 0;
tascam->feedback_pattern_in_idx = 0;
tascam->feedback_pattern_out_idx = 0;
tascam->feedback_synced = false;
tascam->feedback_urb_skip_count = NUM_FEEDBACK_URBS * 2;
/* DEBUG: Log the initial state on prepare. */
dev_info(tascam->card->dev, "Prepare: Sync state reset, starting in unsynced mode.\n");
nominal_frames_per_packet = runtime->rate / 8000;
for (i = 0; i < FEEDBACK_ACCUMULATOR_SIZE; i++)
tascam->feedback_accumulator_pattern[i] = nominal_frames_per_packet;
@ -592,12 +602,23 @@ static void playback_urb_complete(struct urb *urb)
spin_lock_irqsave(&tascam->lock, flags);
/* DEBUG: Log which sizing logic is being used. */
if (tascam->feedback_synced)
dev_info_ratelimited(tascam->card->dev, "Playback: Using DYNAMIC packet sizes (synced).\n");
else
dev_info_ratelimited(tascam->card->dev, "Playback: Using NOMINAL packet sizes (not synced).\n");
for (i = 0; i < PLAYBACK_URB_ISO_PACKETS; i++) {
unsigned int frames_for_packet;
size_t bytes_for_packet;
frames_for_packet = tascam->feedback_accumulator_pattern[tascam->feedback_pattern_out_idx];
tascam->feedback_pattern_out_idx = (tascam->feedback_pattern_out_idx + 1) % FEEDBACK_ACCUMULATOR_SIZE;
if (tascam->feedback_synced) {
frames_for_packet = tascam->feedback_accumulator_pattern[tascam->feedback_pattern_out_idx];
tascam->feedback_pattern_out_idx = (tascam->feedback_pattern_out_idx + 1) % FEEDBACK_ACCUMULATOR_SIZE;
} else {
frames_for_packet = runtime->rate / 8000;
}
bytes_for_packet = frames_for_packet * DEVICE_BYTES_PER_FRAME;
if ((urb_total_bytes + bytes_for_packet) > tascam->playback_urb_alloc_size) {
@ -628,6 +649,9 @@ static void playback_urb_complete(struct urb *urb)
urb->transfer_buffer_length = urb_total_bytes;
/* DEBUG: Log the size of the URB we just prepared. */
dev_info_ratelimited(tascam->card->dev, "Prepared playback URB, total bytes: %zu\n", urb_total_bytes);
if (atomic_read(&tascam->playback_active)) {
urb->dev = tascam->dev;
ret = usb_submit_urb(urb, GFP_ATOMIC);
@ -645,6 +669,8 @@ static void feedback_urb_complete(struct urb *urb)
int ret, i, p;
u64 current_period;
u64 total_frames_in_urb = 0;
bool was_synced;
bool sync_lost_this_urb = false;
if (urb->status == -ENOENT || urb->status == -ECONNRESET || urb->status == -ESHUTDOWN)
return;
@ -659,11 +685,18 @@ static void feedback_urb_complete(struct urb *urb)
if (urb->status != 0) {
dev_warn_ratelimited(tascam->card->dev, "Feedback URB failed with status %d\n", urb->status);
spin_lock_irqsave(&tascam->lock, flags);
if (tascam->feedback_synced)
dev_info(tascam->card->dev, "Sync Lost (URB error)!\n");
tascam->feedback_synced = false;
spin_unlock_irqrestore(&tascam->lock, flags);
goto resubmit;
}
spin_lock_irqsave(&tascam->lock, flags);
was_synced = tascam->feedback_synced;
if (tascam->feedback_urb_skip_count > 0) {
tascam->feedback_urb_skip_count--;
goto unlock_and_resubmit;
@ -674,16 +707,20 @@ static void feedback_urb_complete(struct urb *urb)
const unsigned int *pattern;
int pattern_index;
if (urb->iso_frame_desc[p].status != 0 || urb->iso_frame_desc[p].actual_length < 1)
if (urb->iso_frame_desc[p].status != 0 || urb->iso_frame_desc[p].actual_length < 1) {
sync_lost_this_urb = true;
continue;
}
feedback_value = *((u8 *)urb->transfer_buffer + urb->iso_frame_desc[p].offset);
dev_info_ratelimited(tascam->card->dev, "Feedback received, value: %u\n", feedback_value);
if (feedback_value >= tascam->feedback_base_value &&
feedback_value <= tascam->feedback_max_value) {
pattern_index = feedback_value - tascam->feedback_base_value;
pattern = tascam->feedback_patterns[pattern_index];
} else {
sync_lost_this_urb = true;
pattern = NULL;
}
@ -700,6 +737,17 @@ static void feedback_urb_complete(struct urb *urb)
}
}
/* Update and log the sync state transition. */
if (sync_lost_this_urb) {
if (was_synced)
dev_info(tascam->card->dev, "Sync Lost (bad packet)!\n");
tascam->feedback_synced = false;
} else {
if (!was_synced)
dev_info(tascam->card->dev, "Sync Acquired!\n");
tascam->feedback_synced = true;
}
if (total_frames_in_urb > 0)
tascam->playback_frames_consumed += total_frames_in_urb;

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us144mkii.ko
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