On 04/18/2016 08:43 AM, Richard Genoud wrote: > 2016-04-18 14:34 GMT+02:00 Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>: >> Hi Arnd, >> >> CC Richard (serial-mctrl-gpio) >> CC Grant (ePAPR successor) and Frank >> >> On Sat, Apr 16, 2016 at 6:30 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: >>> On Thursday 14 April 2016 14:13:19 Geert Uytterhoeven wrote: [...] >>>> - out1-gpios: Must contain a GPIO specifier, referring to the GPIO pin to be >>>> used as the UART's OUT1 line. >>>> - out2-gpios: Must contain a GPIO specifier, referring to the GPIO pin to be >>>> used as the UART's OUT2 line. >>> >>> I had to look up what OUT1 and OUT2 are, but I still don't see how you'd >>> implement them using a GPIO line: From all I can tell, these are usually >>> internal registers in a hardware uart but they are not assigned to an >>> external line on the standard db9 or even the old db25 connectors. Should >>> we drop these instead? Yeah, not sure how those snuck in for gpios. The original 8250/16550 uarts had OUT1 and OUT2 pins, and OUT1 could be used like gpio. That was 3 decades ago though so maybe we don't need to try to recreate that tech again :) >> They're indeed fairly exotic, and they're burried deeply in the ns16550 >> datasheet. We do have TIOCM_OUT1 and TIOCM_LOOP in asm-generic/termios.h, >> probably for obscure historical reasons. Please leave the bit defs alone. >> If we drop them, I guess they should be removed from the helper code in >> drivers/tty/serial/serial_mctrl_gpio.c, too? There don't seem to be any >> current users. > I must confess that I don't really know what TIOCM_OUT1&2 are for. > (I implemented them for completeness) > But it seems that OUT2 is used in some drivers: > drivers/tty/serial/omap-serial.c: > /* > * Most PC uarts need OUT2 raised to enable interrupts. > */ > up->port.mctrl |= TIOCM_OUT2; There's no need for OUT1 and OUT2 gpios; let's fix that. Regards, Peter Hurley -- 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
