Add high-speed UART baud rate switching#13
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New CMD_SET_BAUD command lets host negotiate higher baud rates after agent boot. Agent ACKs at current baud, both sides switch, host verifies with INFO at new baud. Falls back on failure. Tested on real hi3516ev300 with FTDI FT232R: - 230400: 22.6 KB/s (98.3% efficiency) - 460800: 44.9 KB/s (97.4% efficiency) - 921600: 83.2 KB/s (90.3% efficiency) 16MB flash dump: ~3.4 min at 921600 vs 24.5 min at 115200 (7.3x faster). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
After switching baud, agent waits 3s for a valid command at the new rate. If nothing arrives (host failed to switch, or link doesn't support the rate), agent reverts to 115200 automatically. Tested: send SET_BAUD 460800 but keep host at 115200 — agent reverts after 3s timeout, host communicates normally at 115200. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Client auto-switches to 921600 baud for transfers >4KB, stays there for subsequent operations (no switching between read/write bauds). Agent reverts to 115200 after ~10s of no valid commands at high baud, so disconnected hosts can always reconnect at the default rate. Tested on hi3516ev300: auto-baud read 72 KB/s, idle fallback after 12s disconnect, reconnect at 115200 confirmed. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
Dynamic baud rate switching for the flash agent. Start at 115200 (bootrom default), negotiate up to 921600 after agent boot.
CMD_SET_BAUD(0x08): host sends desired baud rate, agent ACKs at current baud, both switchuart_set_baud(): reconfigures PL011 IBRD/FBRD with proper TX drain and latch sequenceFlashAgentClient.set_baud(): switches with automatic fallback on verification failureBenchmark (real hi3516ev300, FTDI FT232R, 64KB READ)
Test plan
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