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[usb_uart] Fix FTDI RX data stall / corruption and input restart reliability (#17348)

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Co-authored-by: Oliver Kleinecke <kleinecke.oliver@googlemail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Oliver Kleinecke
2026-07-07 21:55:49 +10:00
committed by GitHub
co-authored by Oliver Kleinecke Claude Sonnet 4.6
parent 40c3a4320f
commit af4a6e7ec3
3 changed files with 50 additions and 16 deletions
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esphome/components/usb_uart/ft23xx.cpp
+38 -14
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@@ -3,6 +3,7 @@
#include "usb_uart.h"
#include "usb/usb_host.h"
#include "esphome/core/log.h"
#include "esphome/core/application.h"
#include "esphome/components/uart/uart_debugger.h"
#include "esphome/components/bytebuffer/bytebuffer.h"
@@ -396,7 +397,14 @@ int USBUartTypeFT23XX::set_dtr_rts_(USBUartChannel *channel) {
}
void USBUartTypeFT23XX::start_input(USBUartChannel *channel) {
if (!channel->initialised_.load() || channel->input_started_.load())
if (!channel->initialised_.load())
return;
// Use compare_exchange_strong to avoid a check-then-act race: start_input() is called
// from both the USB task (self-restart on success) and the main loop (backpressure
// restart), so a plain load()/store() pair can let both threads submit a transfer.
auto started = false;
if (!channel->input_started_.compare_exchange_strong(started, true))
return;
const auto *ep = channel->cdc_dev_.in_ep;
@@ -408,39 +416,55 @@ void USBUartTypeFT23XX::start_input(USBUartChannel *channel) {
return;
}
// FTDI prepends a 2-byte modem/line status header to every bulk IN packet.
size_t uart_data_len = (status.data_len > 2) ? (status.data_len - 2) : 0;
if (uart_data_len > 0) {
ESP_LOGV(TAG, "RX callback: Received %zu bytes, channel=%d", uart_data_len, channel->index_);
if (!channel->dummy_receiver_) {
// Copy the entire received UART payload into the ring buffer in one
// operation to avoid per-byte overhead and reduce the chance of
// heap activity in hot paths.
channel->input_buffer_.push(status.data + 2, uart_data_len);
UsbDataChunk *chunk = this->chunk_pool_.allocate();
if (chunk == nullptr) {
this->usb_data_queue_.increment_dropped_count();
channel->input_started_.store(false);
// Queue is full — wake the main loop to drain it, then let read_array()
// retrigger start_input() rather than spinning here in the USB task.
this->enable_loop_soon_any_context();
App.wake_loop_threadsafe();
return;
}
// Strip the 2-byte FTDI header before queuing.
memcpy(chunk->data, status.data + 2, uart_data_len);
chunk->length = static_cast<uint16_t>(uart_data_len);
chunk->channel = channel;
this->usb_data_queue_.push(chunk);
#ifdef USE_UART_DEBUGGER
if (channel->debug_) {
// Debug path creates a temporary vector for logging only; this is
// acceptable because debug mode is opt-in and not used in release.
uart::UARTDebug::log_hex(uart::UART_DIRECTION_RX,
std::vector<uint8_t>(status.data + 2, status.data + 2 + uart_data_len), ',',
channel->debug_prefix_);
}
#endif
this->enable_loop_soon_any_context();
App.wake_loop_threadsafe();
}
} else {
} else if (status.data_len >= 2) {
ESP_LOGVV(TAG, "RX: Status packet, modem=0x%02X line=0x%02X, ch=%d", status.data[0], status.data[1],
channel->index_);
}
channel->input_started_.store(false);
if (channel->dummy_receiver_ ||
channel->input_buffer_.get_free_space() >= channel->cdc_dev_.in_ep->wMaxPacketSize) {
this->start_input(channel);
}
this->start_input(channel);
};
channel->input_started_.store(true);
this->transfer_in(ep->bEndpointAddress, callback, ep->wMaxPacketSize);
if (!this->transfer_in(ep->bEndpointAddress, callback, ep->wMaxPacketSize)) {
ESP_LOGE(TAG, "RX transfer submission failed for ep=0x%02X", ep->bEndpointAddress);
channel->input_started_.store(false);
}
}
void USBUartTypeFT23XX::on_rx_overflow(USBUartChannel *channel) {
ESP_LOGW(TAG, "RX buffer overflow on channel %d, clearing to resync", channel->index_);
channel->input_buffer_.clear();
}
void USBUartTypeFT23XX::enable_channels() {