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Date: Thu, 27 Aug 2009 15:33:30 +0300
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] RTC polling mode broken
Message-ID: <20090827123330.GO30093@redhat.com>
References: <20090715105043.GA26311@chrom.inf.tu-dresden.de>
	<20090827111803.GA7329@ramdisk>
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To: Bernhard Kauer <kauer@redhat.com>
Cc: qemu-devel@nongnu.org

On Thu, Aug 27, 2009 at 01:18:03PM +0200, Bernhard Kauer wrote:
> Suppose I have some software that does not run with Qemu 
> and I have done the following steps:
> 
> 	1. found that it is bug in Qemu and not in my software
> 	2. produced a patch that fixed the problem for my test-case
> 	3. send the patch with an explanation to the mailinglist
> 	4. waited 6 weeks for comments or inclusion in Qemu
> 
> Now what should I do, to get the bug fixed?
> 
Resend the patch? (no need to what for 6 week to do that BTW)

> 
> Thanks,
> 
> 
> 	Bernhard
> 
> 
> 
> 
> On Wed, Jul 15, 2009 at 12:50:43PM +0200, Bernhard Kauer wrote:
> > The RTC emulation does not set the IRQ flags independent of the IRQ enable bits.
> > 
> > The original MC146818A datasheet from 1984 notes:
> > 	"flag bits in Register C [...] are set independent of the
> > 	state of the corresponding enable bits in Register B"
> > Similar sections can be found in newer documentation e.g. in rtc82885.
> > 
> > Qemu and Bochs set the IRQ flags only if they are enabled,
> > which breaks drivers polling on them.
> > 
> > The following patch corrects this for the update-ended-flag in Qemu only.
> > It currently does not fix the handling of the other flags.
> > 
> > 
> > Signed-off-by: Bernhard Kauer <kauer@tudos.org>
> > 
> > 
> > diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
> > index 2022548..2b040a7 100644
> > --- a/hw/mc146818rtc.c
> > +++ b/hw/mc146818rtc.c
> > @@ -421,9 +421,10 @@ static void rtc_update_second2(void *opaque)
> >      }
> >  
> >      /* update ended interrupt */
> > +    s->cmos_data[RTC_REG_C] |= REG_C_UF;
> >      if (s->cmos_data[RTC_REG_B] & REG_B_UIE) {
> > -        s->cmos_data[RTC_REG_C] |= 0x90;
> > -        rtc_irq_raise(s->irq);
> > +      s->cmos_data[RTC_REG_C] |= REG_C_IRQF;
> > +      rtc_irq_raise(s->irq);
> >      }
> >  
> >      /* clear update in progress bit */
> 
> 

--
			Gleb.