> > +static unsigned long global_flags; > > Is the restriction on concurrent DMA RX streams global or per-device?
? Each device has only one DMA RX channel. Hey Simon, you upstreamed this driver :) Or did I get the question wrong? > > + if (dir == DMA_FROM_DEVICE) > > + clear_bit(SDHI_INTERNAL_DMAC_RX_IN_USE, &global_flags); > > + > > Is clear_bit() expensive? If so it might be worth avoiding on SoCs that > don't have the restriction covered by this patch. It's an atoimc bitop, so maybe has a memory barrier. Hmm, the above version is better on the cache lines, though, if you don't have the restriction. Will think about it and make sure both clear_bit() are in sync.
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