Date: Mon, 2 Feb 2009 15:50:04 +0000 From: Rui Paulo <rpaulo@freebsd.org> To: Andriy Gapon <avg@icyb.net.ua> Cc: freebsd-acpi@FreeBSD.org Subject: Re: piix4 and C2: patch for BRLD_EN_BM/ACPI_BITREG_BUS_MASTER_RLD Message-ID: <66885316-6F5B-4C56-BFE0-DBB86E050C99@freebsd.org> In-Reply-To: <498708FD.9030404@icyb.net.ua> References: <498708FD.9030404@icyb.net.ua>
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This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --Apple-Mail-4--267949195 Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit On 2 Feb 2009, at 14:53, Andriy Gapon wrote: > > Another patch for acpi_cpu code related to PIIX4 chipset. > > We do not support C3 with this chipset and as such we never touch > ACPI_BITREG_BUS_MASTER_RLD when running on it. It's also possible > (probable) that we never reset ACPI_BITREG_BUS_MASTER_STATUS > (because of > CPU_QUIRK_NO_BM_CTRL). > So, if BIOS configures ACPI_BITREG_BUS_MASTER_RLD to 1 and > ACPI_BITREG_BUS_MASTER_STATUS gets set to 1, we would get a situation > where the system would always immediately break out of C2 state should > we ever attempt to enter it. > > Actually, ACPI spec says that bus master activity need not break out > of > C2 state (only interrupts must do that). > > Given all of the above, it seems to be safe and desired to reset > ACPI_BITREG_BUS_MASTER_RLD to zero with this chipset. > > The patch is successfully tested on a real system that exhibited the > above behavior (immediate backout from cx_lowest of C2 to C1). Looks ok to me. I no longer have a PIIX4 system to test it, though. So, if no one raises any objection, I'll commit it to HEAD in a few days. Andriy, if I forget, please ping me :-) Thanks, -- Rui Paulo --Apple-Mail-4--267949195 content-type: application/pgp-signature; x-mac-type=70674453; name=PGP.sig content-description: This is a digitally signed message part content-disposition: inline; filename=PGP.sig content-transfer-encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (Darwin) iEYEARECAAYFAkmHFiwACgkQfD8M/ASTygJ3nwCdEYEF0BUPKYTVr5IHTyvZsTV7 01sAn234kQpWxfljbnQcWlyuYKeWZrI0 =736v -----END PGP SIGNATURE----- --Apple-Mail-4--267949195--
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