On Tue, Nov 10, 2020 at 06:50:32PM +0900, Tomasz Figa wrote: > In what terms it doesn't actually work? Last time I checked some > platforms actually defined CONFIG_DMA_NONCOHERENT, so those would > instead use the kmalloc() + dma_map() path. I don't have any > background on why that was added and whether it needs to be preserved, > though. Kieran, Laurent, do you have any insight? CONFIG_DMA_NONCOHERENT is set on sh and mips for platforms that may support non-coherent DMA at compile time (but at least for mips that doesn't actually means this gets used). Using that ifdef to decide on using usb_alloc_coherent vs letting the usb layer map the data seems at best odd, and if we are unlucky papering over a bug somewhere.
