| From 0c6d2ffcebff88c6cda738aa46fa77c09b93b78b Mon Sep 17 00:00:00 2001 |
| From: Fam Zheng <famz@redhat.com> |
| Date: Thu, 18 May 2017 09:21:27 +0200 |
| Subject: [PATCH 14/18] serial: only resample THR interrupt on rising edge of |
| IER.THRI |
| |
| RH-Author: Fam Zheng <famz@redhat.com> |
| Message-id: <20170518092131.16571-15-famz@redhat.com> |
| Patchwork-id: 75304 |
| O-Subject: [RHEL-7.4 qemu-kvm PATCH v3 14/18] serial: only resample THR interrupt on rising edge of IER.THRI |
| Bugzilla: 1451470 |
| RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com> |
| RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com> |
| RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com> |
| |
| From: Paolo Bonzini <pbonzini@redhat.com> |
| |
| 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> |
| (cherry picked from commit 1645b8eee558ffe2389a081bf61d08a864c36d2c) |
| Signed-off-by: Fam Zheng <famz@redhat.com> |
| Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com> |
| |
| hw/char/serial.c | 25 ++++++++++++++++--------- |
| 1 file changed, 16 insertions(+), 9 deletions(-) |
| |
| diff --git a/hw/char/serial.c b/hw/char/serial.c |
| index e0d29a8..9986adf 100644 |
| |
| |
| @@ -306,10 +306,12 @@ 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); |
| @@ -324,18 +326,23 @@ 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: |
| -- |
| 1.8.3.1 |
| |