* Philippe Mathieu-Daudé (phi...@redhat.com) wrote: > On 8/20/19 3:38 PM, Philippe Mathieu-Daudé wrote: > > On 8/20/19 3:12 PM, John Snow wrote: > >> On 8/20/19 6:25 AM, Philippe Mathieu-Daudé wrote: > >>> [cross posting QEMU & SeaBIOS] > >>> > >>> Hello, > >>> > >>> I'v been looking at a QEMU bug report [1] which bisection resulted in a > >>> SeaBIOS commit: > >>> > >>> 4a6dbcea3e412fe12effa2f812f50dd7eae90955 is the first bad commit > >>> commit 4a6dbcea3e412fe12effa2f812f50dd7eae90955 > >>> Author: Nikolay Nikolov <nick...@users.sourceforge.net> > >>> Date: Sun Feb 4 17:27:01 2018 +0200 > >>> > >>> floppy: Use timer_check() in floppy_wait_irq() > >>> > >>> Use timer_check() instead of using floppy_motor_counter in BDA for the > >>> timeout check in floppy_wait_irq(). > >>> > >>> The problem with using floppy_motor_counter was that, after it reaches > >>> 0, it immediately stops the floppy motors, which is not what is > >>> supposed to happen on real hardware. Instead, after a timeout (like in > >>> the end of every floppy operation, regardless of the result - success, > >>> timeout or error), the floppy motors must be kept spinning for > >>> additional 2 seconds (the FLOPPY_MOTOR_TICKS). So, now the > >>> floppy_motor_counter is initialized to 255 (the max value) in the > >>> beginning of the floppy operation. For IRQ timeouts, a different > >>> timeout is used, specified by the new FLOPPY_IRQ_TIMEOUT constant > >>> (currently set to 5 seconds - a fairly conservative value, but should > >>> work reliably on most floppies). > >>> > >>> After the floppy operation, floppy_drive_pio() resets the > >>> floppy_motor_counter to 2 seconds (FLOPPY_MOTOR_TICKS). > >>> > >>> This is also consistent with what other PC BIOSes do. > >>> > >>> > >>> This commit improve behavior with real hardware, so maybe QEMU is not > >>> modelling something or modelling it incorrectly? > > [...] > >> > >> Well, that's unfortunate. > >> > >> What version of QEMU shipped the SeaBIOS that caused the regression? > > > > See https://bugs.launchpad.net/qemu/+bug/1840719/comments/3 > > > > QEMU commit 0b8f74488e, slighly before QEMU v3.1.0 > > (previous tag is v3.0.0). > > > > But you can use v4.1.0 too, simply change the SeaBIOS bios.bin, i.e.: > > > > qemu$ git checkout v4.1.0 > > > > qemu$ (cd roms/seabios && git checkout 4a6dbcea3e4~) && \ > > make -C roms bios > > > > Now pc-bios/bios.bin is built using the last commit working, > > > > qemu$ (cd roms/seabios && git checkout 4a6dbcea3e4) && \ > > make -C roms bios > > > > And you can reproduce the error. > > Looking at the fdc timer I noticed it use a static '50 ns' magic value.
That's not 50ns > Increasing this value allows the floppy image to boot again, using this > snippet: > > -- >8 -- > diff --git a/hw/block/fdc.c b/hw/block/fdc.c > index 9b24cb9b85..5fc54073fd 100644 > --- a/hw/block/fdc.c > +++ b/hw/block/fdc.c > @@ -2134,7 +2134,7 @@ static void fdctrl_handle_readid(FDCtrl *fdctrl, > int direction) > > cur_drv->head = (fdctrl->fifo[1] >> 2) & 1; > timer_mod(fdctrl->result_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + > - (NANOSECONDS_PER_SECOND / 50)); That's 1/50th of a second in ns. > + (NANOSECONDS_PER_SECOND / 5000)); I'm not too sure about readid; but assuming we're rotating at 360rpm, that's 6 revolutions/second, and 18 sectors/track = 108 sectors/second (half of that for a double density disk). So, the wait for a sector to spin around and read feels like it should be in the region of 1/108 of a second + some latency - so 1/50th of a second would seem to be in the ballpark or being right, where as 1/5000 of a second is way too fast for a poor old floppy. Dave > } > > static void fdctrl_handle_format_track(FDCtrl *fdctrl, int direction) > --- > > Any idea what is the correct value to use here? > > Regards, > > Phil. > _______________________________________________ > SeaBIOS mailing list -- seab...@seabios.org > To unsubscribe send an email to seabios-le...@seabios.org -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK