Hi, On Monday 16 October 2017 07:50 PM, Felipe Balbi wrote: > > Hi, > > Faiz Abbas <[email protected]> writes: >> Hi Felipe, >> >> On Monday 16 October 2017 07:25 PM, Felipe Balbi wrote: >>> >>> Hi, >>> >>> Marek Vasut <[email protected]> writes: >>>> On 10/16/2017 07:21 AM, Faiz Abbas wrote: >>>>> A flush of the cache is required before any outbound DMA access can >>>>> take place. The minimum size that can be flushed from the cache is >>>>> one cache line size. Therefore, any buffer allocated for DMA should >>>>> be in multiples of cache line size. >>>>> >>>>> Thus, allocate memory for ep0_trb in multiples of cache line size. >>>>> >>>>> Also, when local variable trb is assigned to dwc->ep0_trb[1] and used >>>>> to flush cache, it leads to cache misaligned messages as only the base >>>>> address dwc->ep0_trb is cache aligned. >>>>> >>>>> Therefore, flush cache using ep0_trb_addr which is always cache aligned. >>>>> >>>>> Signed-off-by: Faiz Abbas <[email protected]> >>>> >>>> SGTM, Felipe, can you review this please ? >>> >>> is cache maintenance done correctly in u-boot? Isn't the whole idea of a >>> coherent memory area that is is non-cacheable, non-bufferable memory? >>> >>> Also, why isn't the API itself guaranteeing alignment requirements? >>> >> There is no support in u-boot to make a memory area non-cacheable. >> This is the definition of dma_alloc_coherent() >> >> static inline void *dma_alloc_coherent(size_t len, unsigned long *handle) >> { >> *handle = (unsigned long)memalign(ARCH_DMA_MINALIGN, len); >> return (void *)*handle; >> } >> >> This driver is mostly copied from kernel (where dma_alloc_coherent() is >> what you describe) and extra flush_cache functions are added because of >> U-Boot's inability to allocate coherent memory. > > then that's what should be fixed. No? >
You're right but that sounds like a long-term feature which will affect a huge part of u-boot. Until it is implemented, I guess this is the best way to handle the issue. Thanks, Faiz _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
