arm/179688: [patch] [rpi] serial console eats some characters at moutroot prompt

[Luiz Otavio O Souza]

>Number:         179688
>Category:       arm
>Synopsis:       [patch] [rpi] serial console eats some characters at moutroot prompt
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-arm
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Jun 18 19:10:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Luiz Otavio O Souza
>Release:        -head r251700
>Organization:
>Environment:
FreeBSD raspberry-pi 10.0-CURRENT FreeBSD 10.0-CURRENT #11 r251700M: Tue Jun 18 13:06:54 BRT 2013     root at devel:/data/rpi/rpi/obj/arm.armv6/data/rpi/rpi/src/sys/RPI-B  arm
>Description:
While at mountroot prompt the rpi uart driver eats some characters, making very hard to type something right.

ray@ suggested to not enable the uart interrupts in uart_bus_attach() routine for the console device and that seems to also works fine for rpi.
>How-To-Repeat:
Boot a kernel from BOOTP (or boot a kernel from SD card without a valid root partition) and try to type at mountroot prompt. You need to keep the keys pressed for a while to see some output.
>Fix:
Apply the attached patch. It is a copy from the workaround used on uart_dev_imx.c.

Patch attached with submission follows:

Index: dev/uart/uart_dev_pl011.c
===================================================================
--- dev/uart/uart_dev_pl011.c	(revision 251700)
+++ dev/uart/uart_dev_pl011.c	(working copy)
@@ -273,8 +273,13 @@
 	struct uart_bas *bas;
 
 	bas = &sc->sc_bas;
-	/* Enable RX & TX interrupts */
-	__uart_setreg(bas, UART_IMSC, (UART_RXREADY | UART_TXEMPTY));
+	/* XXX workaround to have working console on manut prompt */
+	if (sc->sc_sysdev != NULL && sc->sc_sysdev->type == UART_DEV_CONSOLE){
+		/* Don't enable interrupts */
+	} else {
+		/* Enable RX & TX interrupts */
+		__uart_setreg(bas, UART_IMSC, (UART_RXREADY | UART_TXEMPTY));
+	}
 	/* Clear RX & TX interrupts */
 	__uart_setreg(bas, UART_ICR, IMSC_MASK_ALL);
 


>Release-Note:
>Audit-Trail:
>Unformatted: