Messages in this thread | | | Subject | Re: Proposal for new generic device API: dma_get_required_mask() | From | Krzysztof Halasa <> | Date | Sun, 20 Jun 2004 02:00:42 +0200 |
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Russell King <rmk+lkml@arm.linux.org.uk> writes:
> The SA1111 device and associated sub-device drivers. Basically, Intel > has a "no fix" errata where one of the address bits gets incorrectly > routed to the SDRAM "auto precharge" address bit. This address bit > must be zero, otherwise the SDRAM accesses are messed up.
Well, I knew about it, but I thought it's a "host" problem and device drivers don't have to care.
> You may have a 32MB SDRAM but need to ensure that > physical bit 20 is always zero - IOW you can only DMA from even MB > addresses and not odd MB addresses.
I understand that currently the bit in question is cleared from the masks, and that the ARM/SA1111 dma/pci alloc/map functions know how to handle such mask?
Wouldn't it be better to not touch the masks (which are device capabilities rather than platform limitations) and let alloc/map functions always use the correct half of RAM?
Just asking, I've never worked with such thing. -- Krzysztof Halasa, B*FH - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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