From: Paul <set@pobox.com>
To: linux-kernel@vger.kernel.org
Subject: BUG: invalid MAX_DMA_ADDRESS macro for i386?
Date: Wed, 1 Aug 2001 01:16:52 -0400 [thread overview]
Message-ID: <20010801011651.K225@squish.home.loc> (raw)
Dear All;
2.4.6-ac5 kernel, i486.
Well, I have tracked down my problem. We see a comparison
like this to determine whether to use a bounce buffer:
if ( virt_to_bus(addr+buflen) >= MAX_DMA_ADDRESS) {
...(use a bounce buffer 'cause that addr is not dma-able)...
This is not working, because MAX_DMA_ADDRESS is defined
so:
./include/asm-i386/dma.h:
#define MAX_DMA_ADDRESS (PAGE_OFFSET+0x1000000)
This looks to come out to 0xc1000000. This does not seem
to be comparable to a bus address. eg. 0x100000 == 16M, the DMA
limit on ISA bus.
This driver doesnt work on ISA machine with > 16M, as the
bounce buffer never gets used. (forcing its unconditional use
makes it work fine)
So, what is wrong here? Macro, or conditional? Clue me in
so I can fix it correctly.
Paul
set@pobox.com
next reply other threads:[~2001-08-01 5:17 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-08-01 5:16 Paul [this message]
2001-08-02 14:19 ` Alan Cox
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