drivers: serial: nrf_sw_lpuart: Fix case of flushing RX FIFO - #27571
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In Bluetooth HCI there is a case where uart_fifo_read is called not from the UART interrupt context. If that happens and there is pending UART data then LPUART was not able to reset the receiver as it remained in the blocked state. Case like that happens when HCI device sends data to the host core after host core got reset but before HCI device is reset by the host. Calling uart_fifo_read not from UART interrupt handler is a violation of the API but it has been used like that to drain UART FIFO for years and it has been useful so LPUART adapts to it. Case is fixed by triggering the UART interrupt if receiver is in blocked state. Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>
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In Bluetooth HCI there is a case where uart_fifo_read is called not from the UART interrupt context. If that happens and there is pending UART that then LPUART was not able to reset the receiver. Case like that happend when HCI device sends data to the host core after host core got reset but before HCI device is reset by the host. Calling uart_fifo_read not from UART interrupt handler is a violation of the API but it has been used like that to drain UART FIFO for years and it has been useful so LPUART adapts to it.