3 latency profiles for better buffers for vsts
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serifpersia
parent
ab377f904c
commit
b870235238
155
us144mkii.c
155
us144mkii.c
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@ -67,7 +67,7 @@ MODULE_PARM_DESC(enable, "Enable this US-144MKII soundcard.");
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#define NUM_PLAYBACK_URBS 8
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#define NUM_FEEDBACK_URBS 4
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#define MAX_FEEDBACK_PACKETS 5 // For the highest latency setting
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#define PLAYBACK_URB_ISO_PACKETS 40
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#define MAX_PLAYBACK_URB_ISO_PACKETS 40 // Max possible for allocation (needed for urb_alloc_urb)
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#define FEEDBACK_PACKET_SIZE 3
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#define USB_CTRL_TIMEOUT_MS 1000
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@ -94,6 +94,7 @@ struct tascam_card {
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struct snd_pcm_substream *playback_substream;
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struct urb *playback_urbs[NUM_PLAYBACK_URBS];
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size_t playback_urb_alloc_size;
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unsigned int playback_urb_iso_packets; // Added for dynamic packet count
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struct urb *feedback_urbs[NUM_FEEDBACK_URBS];
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size_t feedback_urb_alloc_size;
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@ -130,17 +131,27 @@ struct tascam_card {
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* Profile | Feedback URB | Approx. Latency | Typical Period Size (Frames)
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* Name | Packet Count | (Hardware) | 48kHz | 96kHz
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* --------|--------------|-----------------|------------|------------
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* Lowest | 1 packet | <= 2ms | <= 96 | <= 192
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* Low | 1 packet | <= 2ms | <= 96 | <= 192
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* Normal | 2 packets | > 2ms to <= 3ms | <= 144 | <= 288
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* High | 5 packets | > 3ms | > 144 | > 288
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* Highest | 5 packets | > 3ms | > 144 | > 288
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*/
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static const unsigned int latency_profile_packets[] = {
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0, // Profile 0 unused
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1, // Low latency
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2, // Normal latency
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5, // High latency
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static const unsigned int hardware_feedback_packet_counts[] = {
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1, // Tier 0: For Low latency (period_frames <= low_profile_thresh_frames)
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2, // Tier 1: For Normal latency (period_frames <= normal_profile_thresh_frames)
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5, // Tier 2: For High latency (period_frames > normal_profile_thresh_frames)
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};
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// New array to map ALSA period size tiers to desired PLAYBACK_URB_ISO_PACKETS
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// This maps to (0:Low, 1:Normal, 2:High) tiers for simplicity
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static const unsigned int playback_iso_packet_counts_tiers[] = {
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8, // Tier 0: For Low latency (e.g., 64-frame buffers)
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24, // Tier 1: For Normal latency (e.g., 128/256-frame buffers)
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40 // Tier 2: For High latency (e.g., 512/1024-frame buffers)
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};
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/*
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* Pre-calculated patterns for frames-per-microframe based on feedback value.
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* These are the core of the "Packet Fixing" engine. Each array represents
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@ -219,10 +230,11 @@ static const struct snd_pcm_hardware tascam_pcm_hw = {
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.channels_min = 2,
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.channels_max = 2,
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.buffer_bytes_max = 1024 * 1024,
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.period_bytes_min = 48 * ALSA_BYTES_PER_FRAME,
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.period_bytes_max = 1024 * ALSA_BYTES_PER_FRAME,
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.periods_min = 2,
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.periods_max = 1024,
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// Adjusted min period size to match the lowest *effective* ASIO buffer (64 samples for 48kHz, etc.)
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.period_bytes_min = 64 * ALSA_BYTES_PER_FRAME, // Corresponds to 'Low' profile's minimum
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.period_bytes_max = 1024 * ALSA_BYTES_PER_FRAME, // Corresponds to 'Highest' profile's maximum
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.periods_min = 2, // Standard double-buffering
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.periods_max = 1024, // Allow for flexible number of periods
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};
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@ -290,9 +302,13 @@ static int tascam_alloc_urbs(struct tascam_card *tascam)
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// Calculate max possible packet size to allocate enough buffer space.
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// Add a margin of 2 for safety.
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// Max frames per packet at 96kHz is 96000/8000 = 12. So 14 frames/packet is safe.
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max_frames_per_packet = (96000 / 8000) + 2;
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max_packet_size = max_frames_per_packet * DEVICE_BYTES_PER_FRAME;
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tascam->playback_urb_alloc_size = max_packet_size * PLAYBACK_URB_ISO_PACKETS;
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// Allocate playback URB buffer size for the absolute maximum possible packets
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// (40, as determined for >5ms latency). This ensures we have enough memory.
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tascam->playback_urb_alloc_size = max_packet_size * MAX_PLAYBACK_URB_ISO_PACKETS;
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if (tascam->playback_urb_alloc_size == 0) {
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dev_err(tascam->card->dev, "Calculated playback_urb_alloc_size is zero.\n");
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@ -300,7 +316,8 @@ static int tascam_alloc_urbs(struct tascam_card *tascam)
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}
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for (i = 0; i < NUM_PLAYBACK_URBS; i++) {
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struct urb *urb = usb_alloc_urb(PLAYBACK_URB_ISO_PACKETS, GFP_KERNEL);
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// URB is allocated with max possible packets, actual # set in hw_params/prepare
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struct urb *urb = usb_alloc_urb(MAX_PLAYBACK_URB_ISO_PACKETS, GFP_KERNEL);
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if (!urb)
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goto error;
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tascam->playback_urbs[i] = urb;
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@ -316,7 +333,7 @@ static int tascam_alloc_urbs(struct tascam_card *tascam)
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urb->interval = 1; // bInterval from descriptor
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urb->context = tascam;
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urb->complete = playback_urb_complete;
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urb->number_of_packets = PLAYBACK_URB_ISO_PACKETS;
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// Do NOT set urb->number_of_packets here. It will be set dynamically in hw_params.
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}
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tascam->feedback_urb_alloc_size = FEEDBACK_PACKET_SIZE * MAX_FEEDBACK_PACKETS;
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@ -363,22 +380,23 @@ static int tascam_pcm_period_size_rule(struct snd_pcm_hw_params *params,
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const struct snd_interval *rate_interval = hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_RATE);
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struct snd_interval new_constraint = { .min = 0, .max = 0, .integer = 1 };
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// Update period size constraints based on your tables for min/max reported ASIO buffers
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switch (rate_interval->min) {
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case 44100:
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new_constraint.min = 49;
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new_constraint.max = 512;
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new_constraint.min = 49; // Lowest profile for 44.1kHz
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new_constraint.max = 512; // Highest profile for 44.1kHz
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break;
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case 48000:
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new_constraint.min = 48;
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new_constraint.max = 512;
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new_constraint.min = 48; // Lowest profile for 48kHz
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new_constraint.max = 512; // Highest profile for 48kHz
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break;
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case 88200:
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new_constraint.min = 98;
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new_constraint.max = 1024;
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new_constraint.min = 98; // Lowest profile for 88.2kHz
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new_constraint.max = 1024; // Highest profile for 88.2kHz
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break;
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case 96000:
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new_constraint.min = 96;
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new_constraint.max = 1024;
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new_constraint.min = 96; // Lowest profile for 96kHz
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new_constraint.max = 1024; // Highest profile for 96kHz
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break;
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default:
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return -EINVAL;
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@ -427,25 +445,71 @@ static int tascam_pcm_hw_params(struct snd_pcm_substream *substream,
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int err, i;
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unsigned int rate = params_rate(params);
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unsigned int period_frames = params_period_size(params);
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unsigned int normal_thresh_ms = 2;
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unsigned int high_thresh_ms = 3;
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int active_latency_profile;
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// ASIO reported buffer sizes (in frames) for each profile at current rate
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unsigned int lowest_asio_frames;
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unsigned int low_asio_frames;
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unsigned int normal_asio_frames;
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unsigned int high_asio_frames;
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int tier_idx; // 0 for Low, 1 for Normal, 2 for High USB packet counts
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unsigned int feedback_urb_packets;
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unsigned int playback_iso_packets;
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// Select a hardware latency profile based on the user's requested period size.
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if (period_frames <= (normal_thresh_ms * rate / 1000)) {
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active_latency_profile = 1; // Low latency (1 feedback packet)
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} else if (period_frames <= (high_thresh_ms * rate / 1000)) {
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active_latency_profile = 2; // Normal latency (2 feedback packets)
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} else {
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active_latency_profile = 3; // High latency (5 feedback packets)
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// Set ASIO reported frame counts based on sample rate from your tables
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switch (rate) {
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case 44100:
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lowest_asio_frames = 49;
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low_asio_frames = 64;
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normal_asio_frames = 128;
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high_asio_frames = 256;
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break;
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case 48000:
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lowest_asio_frames = 48;
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low_asio_frames = 64;
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normal_asio_frames = 128;
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high_asio_frames = 256;
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break;
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case 88200:
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lowest_asio_frames = 98;
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low_asio_frames = 128;
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normal_asio_frames = 256;
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high_asio_frames = 512;
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break;
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case 96000:
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lowest_asio_frames = 96;
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low_asio_frames = 128;
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normal_asio_frames = 256;
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high_asio_frames = 512;
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break;
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default:
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dev_err(tascam->card->dev, "Unsupported sample rate: %u\n", rate);
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return -EINVAL;
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}
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// Determine tier_idx based on requested period_frames for playback_iso_packet_counts_tiers
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// This maps ALSA's requested period_frames to one of your 3 USB packet count tiers.
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// We'll use the 'ASIO Buffer (Reported)' values as our decision points.
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if (period_frames <= low_asio_frames) { // Covers original Lowest, Low
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tier_idx = 0; // Low USB Packet Count (8)
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} else if (period_frames <= normal_asio_frames) { // Covers original Normal
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tier_idx = 1; // Normal USB Packet Count (24)
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} else { // Covers original High, Highest (period_frames > normal_asio_frames)
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tier_idx = 2; // High USB Packet Count (40)
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}
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dev_info(tascam->card->dev,
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"User requested period of %u frames, selecting latency profile %d\n",
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period_frames, active_latency_profile);
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"User requested period of %u frames @ %u Hz, mapping to playback URB tier %d\n",
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period_frames, rate, tier_idx);
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feedback_urb_packets = latency_profile_packets[active_latency_profile];
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// Select feedback_urb_packets based on the determined tier_idx,
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// using the existing logic from latency_profile_packets.
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// Note: The hardware_feedback_packet_counts array is also 0-indexed for these tiers.
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// Tier 0 (low) maps to index 0, Tier 1 (normal) maps to index 1, Tier 2 (high) maps to index 2
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feedback_urb_packets = hardware_feedback_packet_counts[tier_idx];
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playback_iso_packets = playback_iso_packet_counts_tiers[tier_idx];
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tascam->playback_urb_iso_packets = playback_iso_packets; // Store for prepare and complete functions
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// Configure the feedback URBs for the selected latency profile.
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for (i = 0; i < NUM_FEEDBACK_URBS; i++) {
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@ -460,6 +524,13 @@ static int tascam_pcm_hw_params(struct snd_pcm_substream *substream,
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}
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}
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// Configure playback URBs with the dynamically chosen packet count
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for (i = 0; i < NUM_PLAYBACK_URBS; i++) {
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struct urb *urb = tascam->playback_urbs[i];
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urb->number_of_packets = tascam->playback_urb_iso_packets;
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}
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err = snd_pcm_lib_malloc_pages(substream, params_buffer_bytes(params));
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if (err < 0)
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return err;
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@ -487,7 +558,8 @@ static int tascam_pcm_hw_params(struct snd_pcm_substream *substream,
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tascam->feedback_max_value = 98;
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break;
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default:
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dev_err(tascam->card->dev, "Unsupported sample rate for feedback: %u\n", rate);
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// Should not happen if tascam_pcm_period_size_rule is correct
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dev_err(tascam->card->dev, "Unsupported sample rate for feedback patterns: %u\n", rate);
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return -EINVAL;
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}
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@ -535,9 +607,9 @@ static int tascam_pcm_prepare(struct snd_pcm_substream *substream)
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for (i = 0; i < FEEDBACK_ACCUMULATOR_SIZE; i++)
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tascam->feedback_accumulator_pattern[i] = nominal_frames_per_packet;
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// Initialize playback URBs with nominal packet sizes.
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// Initialize playback URBs with nominal packet sizes based on the determined count
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nominal_bytes_per_packet = nominal_frames_per_packet * DEVICE_BYTES_PER_FRAME;
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total_bytes_in_urb = nominal_bytes_per_packet * PLAYBACK_URB_ISO_PACKETS;
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total_bytes_in_urb = nominal_bytes_per_packet * tascam->playback_urb_iso_packets; // Use dynamic value
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if (total_bytes_in_urb > tascam->playback_urb_alloc_size) {
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dev_err(tascam->card->dev, "Prepare: Nominal URB size %zu > allocated %zu\n",
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@ -548,9 +620,12 @@ static int tascam_pcm_prepare(struct snd_pcm_substream *substream)
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for (u = 0; u < NUM_PLAYBACK_URBS; u++) {
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struct urb *urb = tascam->playback_urbs[u];
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// This was already set in hw_params, but good to ensure consistency
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urb->number_of_packets = tascam->playback_urb_iso_packets;
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memset(urb->transfer_buffer, 0, tascam->playback_urb_alloc_size);
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urb->transfer_buffer_length = total_bytes_in_urb;
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for (i = 0; i < PLAYBACK_URB_ISO_PACKETS; i++) {
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for (i = 0; i < tascam->playback_urb_iso_packets; i++) { // Use dynamic value here
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urb->iso_frame_desc[i].offset = i * nominal_bytes_per_packet;
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urb->iso_frame_desc[i].length = nominal_bytes_per_packet;
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}
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@ -663,7 +738,8 @@ static void playback_urb_complete(struct urb *urb)
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spin_lock_irqsave(&tascam->lock, flags);
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// Prepare the next playback URB.
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for (i = 0; i < PLAYBACK_URB_ISO_PACKETS; i++) {
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// Use the dynamic number of packets for this URB
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for (i = 0; i < tascam->playback_urb_iso_packets; i++) {
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unsigned int frames_for_packet;
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size_t bytes_for_packet;
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@ -995,6 +1071,7 @@ static int tascam_probe(struct usb_interface *intf, const struct usb_device_id *
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spin_lock_init(&tascam->lock);
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atomic_set(&tascam->playback_active, 0);
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tascam->current_rate = 0; // Initialize to 0 to force first configuration
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tascam->playback_urb_iso_packets = 0; // Initialize dynamic packet count
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strscpy(card->driver, DRIVER_NAME, sizeof(card->driver));
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strscpy(card->shortname, "TASCAM US-144MKII", sizeof(card->shortname));
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BIN
us144mkii.ko
BIN
us144mkii.ko
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