From: Gerd Hoffmann <kraxel@redhat.com>
To: Don Slutz <Don@cloudswitch.com>
Cc: "Kevin O'Connor" <kevin@koconnor.net>,
seabios@seabios.org, kvm@vger.kernel.org
Subject: Re: [SeaBIOS] [PATCH v2] add acpi pmtimer support
Date: Thu, 06 Sep 2012 07:56:09 +0200 [thread overview]
Message-ID: <50483AF9.60907@redhat.com> (raw)
In-Reply-To: <50477245.4030003@CloudSwitch.Com>
Hi,
>>>> + u32 pmtimer = inl(ioport);
>>>> + return (u64)wraps << 24 | pmtimer;
>>> BTW, why is this "<< 24", and if it should be that way, shouldn't the
>>> pmtimer be "inl(ioport) & 0xffffff" ?
>> The pmtimer is defined to be 24 bits wide, so the shift is correct.
> This is not true in general. It can be either 24 or 32 bits. What it
> is depends on ACPI data (acpi_gbl_FADT->tmr_val_ext).
The piix4 emulated by qemu has 24 bits.
> However it is
> valid to only used 24 bits.
And we certainly want to mask the ioport read (as suggested by kevin and
done in v3 of the patch) so we only pick up the 24 bits we actually use.
thanks
Gerd
prev parent reply other threads:[~2012-09-06 5:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-14 5:29 [PATCH v2] add acpi pmtimer support Gerd Hoffmann
2012-09-02 20:42 ` Kevin O'Connor
2012-09-04 16:28 ` Avi Kivity
2012-09-05 5:27 ` Gerd Hoffmann
2012-09-05 15:39 ` [SeaBIOS] " Don Slutz
2012-09-06 5:56 ` Gerd Hoffmann [this message]
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