Date: Wed, 17 May 2000 15:56:58 -0700 (PDT) From: Jin Guojun (FTG staff) <jin@george.lbl.gov> To: bright@wintelcom.net Cc: hackers@FreeBSD.ORG Subject: Re: How to make system Sync Message-ID: <200005172256.PAA25512@george.lbl.gov>
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Alfred Perlstein <bright@wintelcom.net> stated:
> > I had a couple of system out of sync problems.
> >
> > (1) PCI sync problem:
> > ATM adapter updates a buffer return pointer and generates intr,
> > but when driver pulls out the information that updated by adapter,
> > some memory in the last piece of the pool is garbage.
> > e.g.
> > head -> c0100000
> > tail -> c0100400
> >
> > c0100000 -> buf0
> > c0100004 -> buf1
> > ...
> > c0100100 -> bufn
> > ...
> > c0100160 -> bad address or 0
> > ...
> >
> > If I let driver tsleep() for a while, the problem can be improved.
> > So, it looks like that adapter pushed (DMA) the data into memory,
> > but not been seen by CPU right way due to the DMA sync issue.
> > How can we sync the DMA transaction in BSD?
>
> I think the way you accomplish this is by telling the adapter to
> generate an interrupt when it's completed its DMA operation, you
> seem to be generating interupts at the start instead of the end.
I do not think I have control on when interrupt can be started.
The interrupts are generated when either the # of buffers below
the buffer threshold or the I/O packages greater than I/O threshold.
In Solaris driver, a ddi_dma_sync() routine is used for DMA sync in this case:
#define BCD_FLUSH_CACHE_FOR_HOST(dhandle, offset, length) \
ddi_dma_sync(dhandle, offset, length, DDI_DMA_SYNC_FORKERNEL)
Only thing I am not clear is that reference manual says:
For this adapter, the SDRAM_CTRL register "should" have LB_64_ENB bit set to 1.
There is no further information on this register. I wonder this could cause
the problem since majority PC motherboards have a 32-bit PCI local bus (LB).
-Jin
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