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fix(usb/host): Fix occasional ISOC scheduler skipping transfers

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This commit is contained in:
Tomas Rezucha 2024-07-09 14:10:16 +02:00
parent cb194de911
commit a774e0dfb5
1 changed files with 7 additions and 19 deletions
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26
components/usb/hcd_dwc.c
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@ -44,10 +44,11 @@
#define XFER_LIST_LEN_CTRL 3 // One descriptor for each stage
#define XFER_LIST_LEN_BULK 2 // One descriptor for transfer, one to support an extra zero length packet
// Same length as the frame list makes it easier to schedule. Must be power of 2
// Periodic transfer descriptor lists: Same length as the frame list makes it easier to schedule. Must be power of 2
// FS: Must be 2-64. HS: Must be 8-256. See USB-OTG databook Table 5-47
#define XFER_LIST_LEN_INTR FRAME_LIST_LEN
#define XFER_LIST_LEN_ISOC FRAME_LIST_LEN
#define XFER_LIST_LEN_ISOC 64 // Implement longer ISOC transfer list to give us enough space for additional timing margin
#define XFER_LIST_ISOC_MARGIN 2 // The 1st ISOC transfer is scheduled 2 (micro)frames later so we have enough timing margin
// ------------------------ Flags --------------------------
@ -1982,7 +1983,7 @@ static inline void IRAM_ATTR _buffer_fill_isoc(dma_buffer_block_t *buffer, usb_t
assert(interval > 0);
assert(__builtin_popcount(interval) == 1); // Isochronous interval must be power of 2 according to USB2.0 specification
int total_num_desc = transfer->num_isoc_packets * interval;
assert(total_num_desc <= XFER_LIST_LEN_ISOC);
assert(total_num_desc <= XFER_LIST_LEN_ISOC - XFER_LIST_ISOC_MARGIN); // Some space in the qTD list is reserved for timing margin
int desc_idx = start_idx;
int bytes_filled = 0;
// Zeroize the whole QTD, so we can focus only on the active descriptors
@ -2038,19 +2039,8 @@ static void IRAM_ATTR _buffer_fill(pipe_t *pipe)
if (pipe->multi_buffer_control.buffer_num_to_exec == 0) {
// There are no more previously filled buffers to execute. We need to calculate a new start index based on HFNUM and the pipe's schedule
uint16_t cur_frame_num = usb_dwc_hal_port_get_cur_frame_num(pipe->port->hal);
start_idx = cur_frame_num + 1; // This is the next frame that the periodic scheduler will fetch
uint16_t rem_time = usb_dwc_ll_hfnum_get_frame_time_rem(pipe->port->hal->dev);
// If there is not enough time remaining in this frame, consider the next frame as start index
// The remaining time is in USB PHY clocks. The threshold value is time between buffer fill and execute (6-11us) = 180 + 5 x num_packets
if (rem_time < 195 + 5 * transfer->num_isoc_packets) {
if (rem_time > 165 + 5 * transfer->num_isoc_packets) {
// If the remaining time is +-15 PHY clocks around the threshold value we cannot be certain whether we will schedule it in time for this frame
// Busy wait 10us to be sure that we are at the beginning of next frame/microframe
esp_rom_delay_us(10);
}
start_idx++;
}
start_idx = cur_frame_num + 1; // This is the next frame that the periodic scheduler will fetch
start_idx += XFER_LIST_ISOC_MARGIN; // Start scheduling with a little delay. This will get us enough timing margin so no transfer is skipped
// Only every (interval + offset) transfer belongs to this channel
// Following calculation effectively rounds up to nearest (interval + offset)
@ -2290,9 +2280,7 @@ static inline void _buffer_parse_isoc(dma_buffer_block_t *buffer, bool is_in)
total_actual_num_bytes += transfer->isoc_packet_desc[pkt_idx].actual_num_bytes;
// A descriptor is also allocated for unscheduled frames. We need to skip over them
desc_idx += buffer->flags.isoc.interval;
if (desc_idx >= XFER_LIST_LEN_INTR) {
desc_idx -= XFER_LIST_LEN_INTR;
}
desc_idx %= XFER_LIST_LEN_ISOC;
}
// Write back the actual_num_bytes and statue of entire transfer
assert(total_actual_num_bytes <= transfer->num_bytes);