From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1JtsOz-0004xI-86
	for qemu-devel@nongnu.org; Wed, 07 May 2008 18:46:21 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1JtsOx-0004wA-VO
	for qemu-devel@nongnu.org; Wed, 07 May 2008 18:46:20 -0400
Received: from [199.232.76.173] (port=38668 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1JtsOx-0004vx-Hb
	for qemu-devel@nongnu.org; Wed, 07 May 2008 18:46:19 -0400
Received: from mx1.redhat.com ([66.187.233.31]:37932)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <mtosatti@redhat.com>) id 1JtsOw-0001i0-UV
	for qemu-devel@nongnu.org; Wed, 07 May 2008 18:46:19 -0400
Date: Wed, 7 May 2008 19:49:23 -0300
From: Marcelo Tosatti <mtosatti@redhat.com>
Message-ID: <20080507224923.GA28197@dmt>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Subject: [Qemu-devel] cirrusfb: proper "Attribute Controller Toggle
	Readback" register behaviour
Reply-To: qemu-devel@nongnu.org
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Alan Pevec <apevec@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>
Cc: qemu-devel@nongnu.org


The cirrusfb Linux driver uses the toggle readback register to determine
whether to flip 0xC30 to data/address mode.

Without proper implementation the VGA mode will be erroneously set to
blank resulting in crashes when starting BITBLT.

3d4h index 24h (R):  Attribute Controller Toggle Readback Register
bit    7  If set the Attribute Controller will next access a data register, if
          clear it'll access the index register


Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>


diff --git a/qemu/hw/cirrus_vga.c b/qemu/hw/cirrus_vga.c
index e14ec35..5baac2f 100644
--- a/qemu/hw/cirrus_vga.c
+++ b/qemu/hw/cirrus_vga.c
@@ -1606,13 +1606,15 @@ cirrus_hook_read_cr(CirrusVGAState * s, unsigned reg_index, int *reg_value)
     case 0x17:			// Standard VGA
     case 0x18:			// Standard VGA
 	return CIRRUS_HOOK_NOT_HANDLED;
+    case 0x24:			// Attribute Controller Toggle Readback (R)
+        *reg_value = (s->ar_flip_flop << 7);
+        break;
     case 0x19:			// Interlace End
     case 0x1a:			// Miscellaneous Control
     case 0x1b:			// Extended Display Control
     case 0x1c:			// Sync Adjust and Genlock
     case 0x1d:			// Overlay Extended Control
     case 0x22:			// Graphics Data Latches Readback (R)
-    case 0x24:			// Attribute Controller Toggle Readback (R)
     case 0x25:			// Part Status
     case 0x27:			// Part ID (R)
 	*reg_value = s->cr[reg_index];