This is v3 of a series to convert the 8250 driver to an NBCON console, providing both threaded and atomic printing implementations. v2 of this series is here [0], which also contains additional background information about NBCON consoles in general in the cover letter. To test this version I acquired real hardware (TI AM3358 BeagleBone Black) and tested the following modes: RS232 - no flow control - software flow control (UPF_SOFT_FLOW, UPSTAT_AUTOXOFF) - hardware flow control (UPF_HARD_FLOW, UPSTAT_AUTOCTS, UPSTAT_AUTORTS) - software emulated hardware flow control (UPF_CONS_FLOW, UPSTAT_CTS_ENABLE) RS485 - with SER_RS485_RX_DURING_TX - without SER_RS485_RX_DURING_TX The tests focussed on kernel logging in various combinations of normal, warning, and panic situations. Although not related to the console printing code changes, the tests also included using a getty/login session on the console. Note that this UART (TI16750) supports a 64-byte TX-FIFO, which is used in all console printing modes except for the software emulated hardware flow control. Here are the changes since v2: - For RS485 start/stop TX, specify if called in console context. - For RS485 start/stop TX, when in console context, do not disable/enable interrupts. - Relocate modem_status_handler() to avoid unused static function for some configs. - Move LSR_THRE waiting into a new serial8250_console_wait_putchar() function. - For serial8250_console_fifo_write(), use serial8250_console_putchar() for writing. This allows newline tracking for FIFO mode as well. - For serial8250_console_fifo_write(), allow 10ms timeout for each byte written. - Use FIFO mode for thread and atomic modes when available. - Introduce serial8250_console_byte_write() to handle writing when not using the FIFO mode. - Consolidate thread and atomic callbacks. Now the only difference is modem control: For atomic, called as irq_work. For thread, called direct. John Ogness [0] https://lore.kernel.org/lkml/20240913140538.221708-1-john.ogness@xxxxxxxxxxxxx John Ogness (6): serial: 8250: Adjust the timeout for FIFO mode serial: 8250: Use high-level write function for FIFO serial: 8250: Split out rx stop/start code into helpers serial: 8250: Specify console context for rs485_start/stop_tx serial: 8250: Switch to nbcon console serial: 8250: Revert "drop lockdep annotation from serial8250_clear_IER()" drivers/tty/serial/8250/8250.h | 4 +- drivers/tty/serial/8250/8250_bcm2835aux.c | 4 +- drivers/tty/serial/8250/8250_core.c | 35 ++- drivers/tty/serial/8250/8250_omap.c | 2 +- drivers/tty/serial/8250/8250_port.c | 267 +++++++++++++++++----- include/linux/serial_8250.h | 11 +- 6 files changed, 251 insertions(+), 72 deletions(-) base-commit: 44059790a5cb9258ae6137387e4c39b717fd2ced -- 2.39.5
