linux-kernel - Re: Linux 2.6.30-rc8 [also: VIA Support]

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Date:	Thu, 4 Jun 2009 13:12:43 -0500
From:	"Michael S. Zick" <lkml@...ethan.org>
To:	Harald Welte <HaraldWelte@...tech.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Duane Griffin <duaneg@...da.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.30-rc8 [also: VIA Support]

On Thu June 4 2009, Harald Welte wrote:
> On Thu, Jun 04, 2009 at 11:21:28AM -0500, Michael S. Zick wrote:
> 
> > That is one of my pending questions - -
> > (It is included as a comment at the appropriate point in my patchset.)
> > 
> > The VIA processors have MCR's not MTRR's - -
> 
> AFAIK, that was true for processors like the Winhcip / C6, i.e. earlier than
> the C3.  The C3, C7 and later support 8 intel-style MTRR's.
> 

Super!  A specific breakage!

The c7 setup code is re-using the c6 setup code (MCR's) - -
Will "if 0" out the appropriate parts and arrange for the MTRR setup.

@Linus - -
The Debian/Ubuntu distribution kernels require irqpoll (2.6.28+) -
I took that out very early in my testing, when that problem got fixed -
I will also try putting that back in, it might be needed for
some of its side-effects on the processor/chipset.

> > The C7-M processor uses "in-order retirement" not "out-of-order" - -
> > I think the MCR's **should not** be set for "weak ordered writes" -
> 
> why would it matter on UP? as indicated, I'm not the expert here, but I thought
> memory ordering issues only arise in SMP systems [or possibly with regard to
> DMA, but as we already explored much earlier in this thread, drivers that access
> DMA buffers whil the hardware owns them are buggy and need to be fixed]
> 

I just recall the problems with the pa-risc port (not all machines have coherent I/O);
some have consistent I/O only.  I have one of those also, lucky me. ;)

Mike
> Regards,


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