diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2014-12-12 11:54:42 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2014-12-15 17:34:42 +0100 |
| commit | 1645b8eee558ffe2389a081bf61d08a864c36d2c (patch) | |
| tree | 4f24f749a7b33925e3f7a64d8883866ef12fec17 /hw | |
| parent | 023c3a9707d0d9259a1e858cdf7804dd10973fca (diff) | |
serial: only resample THR interrupt on rising edge of IER.THRI
There is disagreement on whether LSR.THRE should be resampled when
IER.THRI goes from 1 to 1. Bochs only does it if IER.THRI goes from 0
to 1; PCE does it even if IER.THRI is unchanged. But the Windows driver
seems to always go from 1 to 0 and back to 1, so do things in agreement
with Bochs, because the handling of thr_ipending was reported in 2010
(https://lists.gnu.org/archive/html/qemu-devel/2010-03/msg01914.html)
as breaking DR-DOS Plus.
Reported-by: Roy Tam <roytam@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'hw')
| -rw-r--r-- | hw/char/serial.c | 25 |
1 files changed, 16 insertions, 9 deletions
diff --git a/hw/char/serial.c b/hw/char/serial.c index 76054a542a..6d522ff4f3 100644 --- a/hw/char/serial.c +++ b/hw/char/serial.c @@ -336,10 +336,12 @@ static void serial_ioport_write(void *opaque, hwaddr addr, uint64_t val, s->divider = (s->divider & 0x00ff) | (val << 8); serial_update_parameters(s); } else { + uint8_t changed = (s->ier ^ val) & 0x0f; s->ier = val & 0x0f; /* If the backend device is a real serial port, turn polling of the modem - status lines on physical port on or off depending on UART_IER_MSI state */ - if (s->poll_msl >= 0) { + * status lines on physical port on or off depending on UART_IER_MSI state. + */ + if ((changed & UART_IER_MSI) && s->poll_msl >= 0) { if (s->ier & UART_IER_MSI) { s->poll_msl = 1; serial_update_msl(s); @@ -354,18 +356,23 @@ static void serial_ioport_write(void *opaque, hwaddr addr, uint64_t val, * This is not in the datasheet, but Windows relies on it. It is * unclear if THRE has to be resampled every time THRI becomes * 1, or only on the rising edge. Bochs does the latter, and Windows - * always toggles IER to all zeroes and back to all ones. But for - * now leave it as it has always been in QEMU. + * always toggles IER to all zeroes and back to all ones, so do the + * same. * * If IER.THRI is zero, thr_ipending is not used. Set it to zero * so that the thr_ipending subsection is not migrated. */ - if ((s->ier & UART_IER_THRI) && (s->lsr & UART_LSR_THRE)) { - s->thr_ipending = 1; - } else { - s->thr_ipending = 0; + if (changed & UART_IER_THRI) { + if ((s->ier & UART_IER_THRI) && (s->lsr & UART_LSR_THRE)) { + s->thr_ipending = 1; + } else { + s->thr_ipending = 0; + } + } + + if (changed) { + serial_update_irq(s); } - serial_update_irq(s); } break; case 2: |