Date: Fri, 24 Oct 2003 15:28:15 +1000 (EST) From: Bruce Evans <bde@zeta.org.au> To: Rolf Witt <rowi@peanuts.homeunix.org> Cc: freebsd-i386@FreeBSD.org Subject: Re: i386/58458: ATAPI-CDROM DMA Support on ALi Aladdin V Chipset is brocken Message-ID: <20031024152337.B8637@gamplex.bde.org> In-Reply-To: <200310231727.h9NHRMvN082838@peanuts.homeunix.org> References: <200310231727.h9NHRMvN082838@peanuts.homeunix.org>
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On Thu, 23 Oct 2003, Rolf Witt wrote:
> >Description:
> If DMA on IDE-Channel 1 Device 0 aktiv, the DVD-ROM Drive no more works.
> Only PIO works. I have testet this with 2 Drive (both have UDMA33 ability).
> On Pre 4.8 Releases it still functioned.
I forwarded the following usenet article to the author of the bug, but
received no reply.
% Date: Mon, 13 Oct 2003 08:07:01 +0000 (UTC)
% From: viro@parcelfarce.linux.theplanet.co.uk
% Newsgroups: comp.unix.bsd.freebsd.misc
% Subject: Re: Linux vs. FreeBSD (supportability)
%
% In article <3f8a362c$1_2@corp.newsgroups.com>,
% Donn Miller <dmmiller@cvzoom.net> wrote:
%
% >I've had problems with filesystem corruption with both ext2 and ext3,
% >but never ext3.
%
% <shrug> Count the bug reports and see. Most of the cases of fs corruption
% turn out to be either random memory corruption or breakage in underlying
% block device driver. Neither of those cares about fs type, obviously.
%
% If you have real cases of ext2 corruption (not of these two classes and not
% "I had a dirty shutdown and fsck complained about something, I don't remember
% what") - post a bug report.
%
% > I think ext2 is the most crude and cruddy hack of a
% >filesystem ever created. ReiserFS is clearly the best filesystem for
% >Linux right now.
%
% <raised brows>
%
% >Sounds like he must've been compiling his world and kernel with -O3
% >-fomit-frame-pointer -fthread-jumps -funroll-all-loops
% >-fstrength-reduce again. Believe it or not, the default Gentoo
% >optimization flags were along the same lines at one time. The Linux
% >kernel seemed more forgiving in the past of such idiotic optimization
% >levels, but I think he might be getting "more lucky" with Linux in such
% >a situation. Even knowledgeable Linux people will advise against
% >building the kernel with such insane optimizations.
%
% FWIW, that sort of bugs tend to boil down to missing memory barrier or
% missing lock. Not that gcc was too tolerant to anything past -O2, but
% more often than not the real problem is in the code. BTDT...
%
% Idiocy happens. Case in point: while digging through ata-dma.c in 4.9-RC
% a couple of hours ago, I've found the following gem:
%
% switch(ATA_PIO0 + apiomode) {
% case ATA_PIO0: timing = 0x006d0003;
% case ATA_PIO1: timing = 0x00580002;
% case ATA_PIO2: timing = 0x00440001;
% case ATA_PIO3: timing = 0x00330001;
% case ATA_PIO4: timing = 0x00310001;
% default: timing = 0x006d0003;
% }
%
% (M5229 support, in case you wonder and no, -CURRENT doesn't have that bug).
% Had been there for quite a while and that's exactly the sort of bug that
% is harder to find. I'd seen equivalents blamed on compiler, OS, hardware,
% admin, yadda, yadda. Usually ends up with massive blushing when you
% finally realize that yes, it was _that_ dumb...
%
%
Bruce
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