From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39902) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XzPaB-0006tk-TX for qemu-devel@nongnu.org; Fri, 12 Dec 2014 07:44:38 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XzPZz-0001mb-CW for qemu-devel@nongnu.org; Fri, 12 Dec 2014 07:44:28 -0500 Received: from mail-wi0-x230.google.com ([2a00:1450:400c:c05::230]:55446) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XzPZz-0001mJ-5s for qemu-devel@nongnu.org; Fri, 12 Dec 2014 07:44:19 -0500 Received: by mail-wi0-f176.google.com with SMTP id ex7so2351153wid.15 for ; Fri, 12 Dec 2014 04:44:18 -0800 (PST) Sender: Paolo Bonzini From: Paolo Bonzini Date: Fri, 12 Dec 2014 13:44:03 +0100 Message-Id: <1418388243-1886-5-git-send-email-pbonzini@redhat.com> In-Reply-To: <1418388243-1886-1-git-send-email-pbonzini@redhat.com> References: <1418388243-1886-1-git-send-email-pbonzini@redhat.com> Subject: [Qemu-devel] [PATCH v3 4/4] serial: only resample THR interrupt on rising edge of IER.THRI List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: imammedo@redhat.com, andrey@xdel.ru, dgilbert@redhat.com, batuzovk@ispras.ru 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 Signed-off-by: Paolo Bonzini --- 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 0a6747c..5488900 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 { + int 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: -- 1.8.3.1