On Sat, Mar 03, 2018 at 07:19:06PM +0100, Fredrik Noring wrote:
> Christoph, Alan,
>
> > If it is allocating / freeing this memory all the time in the hot path
> > it should really use a dma pool (see include/ilinux/dmapool.h).
> > The dma coherent APIs aren't really built for being called in the
> > hot path.
>
> hcd_buffer_free uses a combination of dma pools and dma coherent APIs:
>
> ...
> for (i = 0; i < HCD_BUFFER_POOLS; i++) {
> if (size <= pool_max[i]) {
> dma_pool_free(hcd->pool[i], addr, dma);
> return;
> }
> }
> dma_free_coherent(hcd->self.sysdev, size, addr, dma);
>
> Alan, can dma_free_coherent be delayed to a point when IRQs are enabled?
The point is that you should always use a pool, period.
dma_alloc*/dma_free* are fundamentally expensive operations on my
architectures, so if you call them from a fast path you are doing
something wrong.
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