Messages in this thread | | | Date | Fri, 18 Jun 2004 11:58:09 -0700 | From | Matt Porter <> | Subject | Re: DMA API issues |
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On Fri, Jun 18, 2004 at 07:19:58PM +0100, Ian Molton wrote: > On Fri, 18 Jun 2004 11:07:21 -0700 > Matt Porter <mporter@kernel.crashing.org> wrote: > > > Can't you just implement an arch-specific allocator for your 32KB > > SRAM, then implement the DMA API streaming and dma_alloc/free APIs > > on top of that? > > Yes but thats not very generic is it? Im not the only one with this > problem.
Yes, it's suboptimal, but an option.
> > Since this architecture is obviously not designed > > for performance > > What makes you think writes to the 32K SRAM are any slower than to the > SDRAM? the device is completely memory mapped.
I was referring to the small amount of space allowed for DMA operations, obviously not the speed of accessing SRAM.
> >, it doesn't seem to be a big deal to have the streaming > > APIs copy to/from the kmalloced (or whatever) buffer to/from the SRAM > > allocated memory and then have those APIs return the proper dma_addr_t > > for the embedded OHCI's address space view of the SRAM. > > Again its a suboptimal solution, and on an architecture where the CPU > isnt *that* fast in the first place it seems wrong to deliberately > choose the slowest possible route...
Ok, so you're looking for a complete change to the streaming DMA APIs, I guess. Possibly requiring another call to allocate streaming-capable memory since kmalloced buffers can't be used directly on your arch (or all arches). I agree it's suboptimal, it's one option to make it work in the current API.
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