serial console vs suspend

It seems that the serial console, or rather a UART used by it, may require
re-initialization after waking up (from suspend to RAM).  At least one of my
systems fails to wake up properly if I configure the serial console.  I've done
some experimenting with cu (and without the console) and the UART seems to be in
some weird state, it echoes back the input and does not send anything on the
wire.  I guess that trying to print to the serial console while the UART is in
that state results in a hang.

To test the theory I made this hack and it does help:
Index: sys/dev/uart/uart_tty.c
===================================================================
--- sys/dev/uart/uart_tty.c	(revision 333667)
+++ sys/dev/uart/uart_tty.c	(working copy)
_at__at_ -114,6 +114,13 _at__at_ uart_cninit(struct consdev *cp)
 	uart_init(di);
 }

+void uart_resume(void);
+void
+uart_resume(void)
+{
+	uart_init(&uart_console);
+}
+
 static void
 uart_cnterm(struct consdev *cp)
 {
Index: sys/x86/acpica/acpi_wakeup.c
===================================================================
--- sys/x86/acpica/acpi_wakeup.c	(revision 333667)
+++ sys/x86/acpica/acpi_wakeup.c	(working copy)
_at__at_ -204,6 +205,8 _at__at_ acpi_wakeup_cpus(struct acpi_softc *sc)
 }
 #endif

+extern void uart_resume(void);
+
 int
 acpi_sleep_machdep(struct acpi_softc *sc, int state)
 {
_at__at_ -300,6 +303,7 _at__at_ acpi_sleep_machdep(struct acpi_softc *sc, int stat
 #else
 		npxresume(susppcbs[0]->sp_fpususpend);
 #endif
+		uart_resume();
 	}

 	return (1);	/* wakeup successfully */


===================================================================

This is quick and dirty, of course.
I think that this should go through the console layer.
And, obviously, not all consoles actually need such a reinit.

So, maybe:
cnresume()
{
	for each console {
		if cn->cn_ops->cn_resume != NULL
			cn->cn_ops->cn_resume(cn)
	}
}

uart_resume(struct consdev *cp)
{
	uart_init(cp->cn_arg);
}

What do you think?

Hmm, it looks like CONSOLE_DRIVER() does not allow to omit a console method.
So, will I have to add a dummy resume to all console drivers?


-- 
Andriy Gapon