Date: Wed, 30 Jan 2013 11:05:24 +0100 From: "Ronald Klop" <ronald-freebsd8@klop.yi.org> To: svn-src-all@freebsd.org Subject: Re: svn commit: r246016 - head/sys/dev/uart Message-ID: <op.wrpyband8527sy@ronaldradial.versatec.local> In-Reply-To: <201301272333.r0RNXhuO031356@svn.freebsd.org> References: <201301272333.r0RNXhuO031356@svn.freebsd.org>
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On Mon, 28 Jan 2013 00:33:43 +0100, Colin Percival <cperciva@freebsd.org> wrote: > Author: cperciva > Date: Sun Jan 27 23:33:42 2013 > New Revision: 246016 > URL: http://svnweb.freebsd.org/changeset/base/246016 > > Log: > 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). > On those buggy emulated UARTs, the "TX idle" interrupt gets lost; with > this workaround, we spinwait for the TX to happen and then send > ourselves > the interrupt. It's ugly but it works, while minimizing the impact on > the code for the !broken_txfifo case. > MFC after: 2 weeks Would hw.uart.broken_txfifo not be a better name? It looks more in line with the other devices under hw.* and avoids naming collisions. Regards, Ronald. > > Modified: > head/sys/dev/uart/uart_dev_ns8250.c > > Modified: head/sys/dev/uart/uart_dev_ns8250.c > ============================================================================== > --- head/sys/dev/uart/uart_dev_ns8250.c Sun Jan 27 23:21:51 > 2013 (r246015) > +++ head/sys/dev/uart/uart_dev_ns8250.c Sun Jan 27 23:33:42 > 2013 (r246016) > @@ -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> > @@ -845,6 +847,11 @@ 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) > { > @@ -862,7 +869,12 @@ 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); > } > _______________________________________________ > svn-src-all@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/svn-src-all > To unsubscribe, send any mail to "svn-src-all-unsubscribe@freebsd.org"
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