Date: Sun, 10 Feb 2013 17:50:56 +0000 (UTC) From: Colin Percival <cperciva@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-8@freebsd.org Subject: svn commit: r246626 - stable/8/sys/dev/uart Message-ID: <201302101750.r1AHouXD053121@svn.freebsd.org>
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Author: cperciva Date: Sun Feb 10 17:50:56 2013 New Revision: 246626 URL: http://svnweb.freebsd.org/changeset/base/246626 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/8/sys/dev/uart/uart_dev_ns8250.c Directory Properties: stable/8/sys/ (props changed) stable/8/sys/dev/ (props changed) stable/8/sys/dev/uart/ (props changed) Modified: stable/8/sys/dev/uart/uart_dev_ns8250.c ============================================================================== --- stable/8/sys/dev/uart/uart_dev_ns8250.c Sun Feb 10 17:48:46 2013 (r246625) +++ stable/8/sys/dev/uart/uart_dev_ns8250.c Sun Feb 10 17:50:56 2013 (r246626) @@ -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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