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From 0c6d2ffcebff88c6cda738aa46fa77c09b93b78b Mon Sep 17 00:00:00 2001
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From: Fam Zheng <famz@redhat.com>
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Date: Thu, 18 May 2017 09:21:27 +0200
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Subject: [PATCH 14/18] serial: only resample THR interrupt on rising edge of
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IER.THRI
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RH-Author: Fam Zheng <famz@redhat.com>
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Message-id: <20170518092131.16571-15-famz@redhat.com>
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Patchwork-id: 75304
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O-Subject: [RHEL-7.4 qemu-kvm PATCH v3 14/18] serial: only resample THR interrupt on rising edge of IER.THRI
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Bugzilla: 1451470
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
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From: Paolo Bonzini <pbonzini@redhat.com>
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There is disagreement on whether LSR.THRE should be resampled when
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IER.THRI goes from 1 to 1. Bochs only does it if IER.THRI goes from 0
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to 1; PCE does it even if IER.THRI is unchanged. But the Windows driver
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seems to always go from 1 to 0 and back to 1, so do things in agreement
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with Bochs, because the handling of thr_ipending was reported in 2010
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(https://lists.gnu.org/archive/html/qemu-devel/2010-03/msg01914.html)
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as breaking DR-DOS Plus.
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Reported-by: Roy Tam <roytam@gmail.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 1645b8eee558ffe2389a081bf61d08a864c36d2c)
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Signed-off-by: Fam Zheng <famz@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/char/serial.c | 25 ++++++++++++++++---------
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1 file changed, 16 insertions(+), 9 deletions(-)
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diff --git a/hw/char/serial.c b/hw/char/serial.c
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index e0d29a8..9986adf 100644
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--- a/hw/char/serial.c
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+++ b/hw/char/serial.c
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@@ -306,10 +306,12 @@ static void serial_ioport_write(void *opaque, hwaddr addr, uint64_t val,
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s->divider = (s->divider & 0x00ff) | (val << 8);
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serial_update_parameters(s);
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} else {
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+ uint8_t changed = (s->ier ^ val) & 0x0f;
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s->ier = val & 0x0f;
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/* If the backend device is a real serial port, turn polling of the modem
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- status lines on physical port on or off depending on UART_IER_MSI state */
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- if (s->poll_msl >= 0) {
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+ * status lines on physical port on or off depending on UART_IER_MSI state.
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+ */
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+ if ((changed & UART_IER_MSI) && s->poll_msl >= 0) {
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if (s->ier & UART_IER_MSI) {
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s->poll_msl = 1;
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serial_update_msl(s);
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@@ -324,18 +326,23 @@ static void serial_ioport_write(void *opaque, hwaddr addr, uint64_t val,
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* This is not in the datasheet, but Windows relies on it. It is
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* unclear if THRE has to be resampled every time THRI becomes
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* 1, or only on the rising edge. Bochs does the latter, and Windows
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- * always toggles IER to all zeroes and back to all ones. But for
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- * now leave it as it has always been in QEMU.
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+ * always toggles IER to all zeroes and back to all ones, so do the
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+ * same.
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*
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* If IER.THRI is zero, thr_ipending is not used. Set it to zero
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* so that the thr_ipending subsection is not migrated.
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*/
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- if ((s->ier & UART_IER_THRI) && (s->lsr & UART_LSR_THRE)) {
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- s->thr_ipending = 1;
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- } else {
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- s->thr_ipending = 0;
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+ if (changed & UART_IER_THRI) {
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+ if ((s->ier & UART_IER_THRI) && (s->lsr & UART_LSR_THRE)) {
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+ s->thr_ipending = 1;
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+ } else {
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+ s->thr_ipending = 0;
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+ }
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+ }
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+
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+ if (changed) {
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+ serial_update_irq(s);
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}
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- serial_update_irq(s);
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}
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break;
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case 2:
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--
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1.8.3.1
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