From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Robert Hancock <hancockr@shaw.ca>
Cc: Mark Lord <liml@rtr.ca>, Allen Martin <AMartin@nvidia.com>,
Jeff Garzik <jeff@garzik.org>, Tejun Heo <htejun@gmail.com>,
Gabor Gombas <gombasg@sztaki.hu>,
linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org,
Kuan Luo <kluo@nvidia.com>, Peer Chen <pchen@nvidia.com>
Subject: Re: sata_nv + ADMA + Samsung disk problem
Date: Fri, 04 Jan 2008 16:51:38 +1100 [thread overview]
Message-ID: <1199425898.7291.30.camel@pasglop> (raw)
In-Reply-To: <477D8F4B.6000601@shaw.ca>
On Thu, 2008-01-03 at 19:43 -0600, Robert Hancock wrote:
> Benjamin Herrenschmidt wrote:
> >> Another thing about the PacDigi core: one has to be very careful
> >> to avoid sequential accesses to sequential PCI locations when
> >> programming the chip -- it cannot handle merged register writes.
> >>
> >> So for any group of sequentially laid out registers, the code has
> >> to ensure it never writes two adjacent registers in sequence..
> >
> > Ugh ? Write combining isn't permitted on normal registers afaik...
> >
> > Ben.
>
> Byte merging can be done by the chipset on MMIO writes (merging multiple
> 8 or 16-bit writes into a single 32-bit cycle).
That is true, if they are consecutive. You mean that this HW is f*cked
up enough to actually have separate 8/16 bits registers that are
contiguous ? Yuck... I'm afraid you -have- to add reads in between to
guarantee that no merging will occur.
Cheers,
Ben.
next prev parent reply other threads:[~2008-01-04 5:52 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-08 12:08 sata_nv + ADMA + Samsung disk problem Gabor Gombas
2007-08-14 9:30 ` Tejun Heo
2007-08-14 12:02 ` Gabor Gombas
2007-08-16 16:06 ` Gabor Gombas
2007-08-16 18:45 ` Jim Paris
2008-01-01 16:44 ` Gabor Gombas
2008-01-02 3:25 ` Tejun Heo
2008-01-02 4:03 ` Robert Hancock
2008-01-02 4:20 ` Robert Hancock
2008-01-02 4:25 ` Tejun Heo
2008-01-02 6:19 ` Jeff Garzik
2008-01-02 6:39 ` Robert Hancock
2008-01-02 6:55 ` Tejun Heo
2008-01-03 0:27 ` Robert Hancock
2008-01-02 17:23 ` Allen Martin
2008-01-02 17:23 ` Allen Martin
2008-01-02 18:57 ` Jeff Garzik
2008-01-02 23:23 ` Allen Martin
2008-01-02 23:23 ` Allen Martin
2008-01-03 0:21 ` Robert Hancock
2008-01-03 4:14 ` Mark Lord
2008-01-03 4:17 ` Mark Lord
2008-01-03 4:54 ` Robert Hancock
2008-01-03 15:44 ` Mark Lord
2008-01-03 15:47 ` Mark Lord
2008-01-03 21:13 ` Benjamin Herrenschmidt
2008-01-04 1:43 ` Robert Hancock
2008-01-04 5:51 ` Benjamin Herrenschmidt [this message]
2008-01-04 0:41 ` Allen Martin
2008-01-04 0:41 ` Allen Martin
2008-01-04 2:51 ` Robert Hancock
2008-01-08 0:10 ` Robert Hancock
2008-01-11 23:18 ` Gabor Gombas
2008-01-12 1:10 ` Robert Hancock
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