On Fri, Sep 26, 2014 at 02:59:18PM +0200, Janusz Użycki wrote: > But serial8250_get_mctrl() in 8250_core.c calls serial8250_modem_status() > which calls eg. uart_handle_cts_change() even if enable_ms() wasn't called. > This is the difference. > The serial8250_modem_status() is also called in the interrupt > and, what I don't understand, in serial8250_console_write(). Reading the MSR register clears the interrupts. So, whenever MSR is read, you have to deal with any state changes which _would_ have been passed to the interrupt function. Plus, it's not quite as you make out above. If enable_ms() is not called, then UART_IER_MSI will not be set in up->ier. Hence, uart_handle_cts_change() will not be called. The reason for the call in the console function is to account for the state changes during console write with CTS flow control - this again needs the MSR register to be read, and we have to account for MSR state changes after the console write has completed. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
