Author: cperciva
Date: Sun Feb 10 17:48:46 2013
New Revision: 246625
URL: http://svnweb.freebsd.org/changeset/base/246625
Log:
MFC r246016:
Add a loader tunable "hw.broken_txfifo" which enables a workaround for a
bug in old versions of QEMU (and Xen, and other places using QEMU code).
Modified:
stable/9/sys/dev/uart/uart_dev_ns8250.c
Directory Properties:
stable/9/sys/ (props changed)
stable/9/sys/dev/ (props changed)
Modified: stable/9/sys/dev/uart/uart_dev_ns8250.c
==============================================================================
--- stable/9/sys/dev/uart/uart_dev_ns8250.c Sun Feb 10 17:10:07 2013
(r246624)
+++ stable/9/sys/dev/uart/uart_dev_ns8250.c Sun Feb 10 17:48:46 2013
(r246625)
@@ -31,6 +31,8 @@ __FBSDID("$FreeBSD$");
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/conf.h>
+#include <sys/kernel.h>
+#include <sys/sysctl.h>
#include <machine/bus.h>
#include <dev/uart/uart.h>
@@ -842,6 +844,11 @@ ns8250_bus_setsig(struct uart_softc *sc,
return (0);
}
+static int broken_txfifo = 0;
+SYSCTL_INT(_hw, OID_AUTO, broken_txfifo, CTLFLAG_RW | CTLFLAG_TUN,
+ &broken_txfifo, 0, "UART FIFO has QEMU emulation bug");
+TUNABLE_INT("hw.broken_txfifo", &broken_txfifo);
+
static int
ns8250_bus_transmit(struct uart_softc *sc)
{
@@ -859,7 +866,12 @@ ns8250_bus_transmit(struct uart_softc *s
uart_setreg(bas, REG_DATA, sc->sc_txbuf[i]);
uart_barrier(bas);
}
- sc->sc_txbusy = 1;
+ if (broken_txfifo)
+ ns8250_drain(bas, UART_DRAIN_TRANSMITTER);
+ else
+ sc->sc_txbusy = 1;
uart_unlock(sc->sc_hwmtx);
+ if (broken_txfifo)
+ uart_sched_softih(sc, SER_INT_TXIDLE);
return (0);
}
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