From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([208.118.235.92]:51444)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <jan.kiszka@siemens.com>) id 1T9Hlr-0001bH-4B
	for qemu-devel@nongnu.org; Wed, 05 Sep 2012 11:44:11 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <jan.kiszka@siemens.com>) id 1T9Hll-0006HK-AZ
	for qemu-devel@nongnu.org; Wed, 05 Sep 2012 11:44:03 -0400
Received: from david.siemens.de ([192.35.17.14]:15669)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <jan.kiszka@siemens.com>) id 1T9Hll-0006H4-11
	for qemu-devel@nongnu.org; Wed, 05 Sep 2012 11:43:57 -0400
Message-ID: <50477334.5000508@siemens.com>
Date: Wed, 05 Sep 2012 17:43:48 +0200
From: Jan Kiszka <jan.kiszka@siemens.com>
MIME-Version: 1.0
References: <1346640974-30974-1-git-send-email-mmogilvi_qemu@miniinfo.net>
	<1346640974-30974-6-git-send-email-mmogilvi_qemu@miniinfo.net>
	<50446F9A.4070809@web.de>
	<alpine.LFD.2.00.1209041448520.8926@eddie.linux-mips.org>
	<5046135B.2080200@redhat.com> <20120905043346.GA7965@comcast.net>
In-Reply-To: <20120905043346.GA7965@comcast.net>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH v4 5/5] i8259: fix dynamically masking
 slave IRQs with IMR register
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Matthew Ogilvie <mmogilvi_qemu@miniinfo.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org, "Maciej W. Rozycki" <macro@linux-mips.org>

On 2012-09-05 06:33, Matthew Ogilvie wrote:
> According to later discussion, the main issue is actually the input
> IRQ behavior on a high to low transition; hence the following fixes
> both the test program and the Microport UNIX problem:
> 
> diff --git a/hw/i8259.c b/hw/i8259.c
> index 6587666..c011787 100644
> --- a/hw/i8259.c
> +++ b/hw/i8259.c
> @@ -143,22 +143,23 @@ static void pic_set_irq(void *opaque, int irq, int level)
>      if (s->elcr & mask) {
>          /* level triggered */
>          if (level) {
>              s->irr |= mask;
>              s->last_irr |= mask;
>          } else {
>              s->irr &= ~mask;
>              s->last_irr &= ~mask;
>          }
>      } else {
>          /* edge triggered */
>          if (level) {
>              if ((s->last_irr & mask) == 0) {
>                  s->irr |= mask;
>              }
>              s->last_irr |= mask;
>          } else {
> +            s->irr &= ~mask;
>              s->last_irr &= ~mask;
>          }
>      }
>      pic_update_irq(s);
>  }
>  
> 
> Perhaps it would be worth it to swap around the "if"s a little bit
> to avoid the (!level) duplication, and clarify that the only difference
> is in the low to high transition?

Yes, refactoring would be welcome. But I would suggest to do this in two
patches, leaving the above change (+ changelog that explains the reason)
in its current clarity.

Hurray, no vmstate subsections needed! :)

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux