On Jun 3, 2004, at 5:06 AM, Pantelis Antoniou wrote:
> 1. dma_map_single finally calls virt_to_bus, which is simplified
> to:
> return (unsigned long)address - KERNELBASE + PCI_DRAM_OFFSET;
>
> PCI_DRAM_OFFSET is defined to be pci_dram_offset.
> Typically it is set be 0 for most arches without pci.
It's typically set to zero for all architectures.
> How could we overide it with a constant 0 so that we avoid the
> memory access?
What memory access?
> 2. How soon in the init sequence could we call dma_alloc_consistent?
Not soon enough.
> For example when setting up a serial console on 8xx I need memory
> for the fifos, and I have to revert in using m8xx_hostalloc which
> IMO should be already dead.
As you pointed out, that is going to have to stay for a while. The
CPM and peripherals must do DMA long before the generic
supporting functions are ready.
> If we could arrange for consistent_alloc to be able to operate with
> a fixed memory area until the memory initialization is complete
> it would make my life much easier and we could finally kill
> m8xx_hostalloc & friends.
I don't think it is worth the complication.
-- Dan
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