From 332cda07c00e3fd29889437c2de4d5dfcd10c6a3 Mon Sep 17 00:00:00 2001
From: Peter Grehan <grehan@FreeBSD.org>
Date: Thu, 12 Apr 2012 18:46:48 +0000
Subject: [PATCH] Complete polled-mode operation by using a callout if the
 device will be used in polled-mode. The callout invokes uart_intr, which
 rearms the timeout. Implemented for bhyve, but generically useful for e.g.
 embedded bringup when the interrupt controller hasn't been setup, or if it's
 not deemed worthy to wire an interrupt line from a serial port.

Submitted by:	neel
Reviewed by:	marcel
Obtained from:	NetApp
MFC after:	3 weeks
---
 sys/dev/uart/uart_bus.h  |  1 +
 sys/dev/uart/uart_core.c | 15 ++++++++++++++-
 sys/dev/uart/uart_if.m   |  1 +
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/sys/dev/uart/uart_bus.h b/sys/dev/uart/uart_bus.h
index b1498f5f0a9..01752d0592c 100644
--- a/sys/dev/uart/uart_bus.h
+++ b/sys/dev/uart/uart_bus.h
@@ -87,6 +87,7 @@ struct uart_softc {
 	struct resource *sc_ires;	/* Interrupt resource. */
 	void		*sc_icookie;
 	int		sc_irid;
+	struct callout	sc_timer;
 
 	int		sc_callout:1;	/* This UART is opened for callout. */
 	int		sc_fastintr:1;	/* This UART uses fast interrupts. */
diff --git a/sys/dev/uart/uart_core.c b/sys/dev/uart/uart_core.c
index fb1bb643304..47d5f3d9771 100644
--- a/sys/dev/uart/uart_core.c
+++ b/sys/dev/uart/uart_core.c
@@ -58,6 +58,12 @@ SLIST_HEAD(uart_devinfo_list, uart_devinfo) uart_sysdevs =
 
 static MALLOC_DEFINE(M_UART, "UART", "UART driver");
 
+#ifndef	UART_POLL_FREQ
+#define	UART_POLL_FREQ		50
+#endif
+static int uart_poll_freq = UART_POLL_FREQ;
+TUNABLE_INT("debug.uart_poll_freq", &uart_poll_freq);
+
 void
 uart_add_sysdev(struct uart_devinfo *di)
 {
@@ -257,6 +263,12 @@ uart_intr(void *arg)
 		if (ipend & SER_INT_TXIDLE)
 			uart_intr_txidle(sc);		
 	}
+
+	if (sc->sc_polled) {
+		callout_reset(&sc->sc_timer, hz / uart_poll_freq,
+		    (timeout_t *)uart_intr, sc);
+	}
+
 	return((flag)?FILTER_HANDLED:FILTER_STRAY);
 }
 
@@ -440,8 +452,9 @@ uart_bus_attach(device_t dev)
 		}
 	}
 	if (sc->sc_ires == NULL) {
-		/* XXX no interrupt resource. Force polled mode. */
+		/* No interrupt resource. Force polled mode. */
 		sc->sc_polled = 1;
+		callout_init(&sc->sc_timer, 1);
 	}
 
 	sc->sc_rxbufsz = 384;
diff --git a/sys/dev/uart/uart_if.m b/sys/dev/uart/uart_if.m
index 0bb145490ed..bfac0713448 100644
--- a/sys/dev/uart/uart_if.m
+++ b/sys/dev/uart/uart_if.m
@@ -26,6 +26,7 @@
 # $FreeBSD$
 
 #include <sys/param.h>
+#include <sys/systm.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/bus.h>