On Thu, Apr 14, 2016 at 12:46:47PM +0000, David Fisher wrote: > dwc3 is in dual-role, with "synopsys,dwc3" specified in DT. > > When xhci is probed, initiated from dwc3/host.c (not DT), we get : > xhci-hcd: probe of xhci-hcd.7.auto failed with error -5 > This -EIO error originated from inside dma_set_mask() down in include/asm-generic/dma-mapping-common.h > > If "generic-xhci" is specified in DT instead, it probes fine as a host-only dwc3 > The difference between DT initiated probe and dwc3 initiated probe is that > when DT initiated probe gets to dma_supported, dma_supported is > implemented by swiotlb_dma_supported (previously set up by a DT call to arch_dma_setup_ops). > Whereas when dwc3 initiated xhci probe gets to dma_supported, arch_dma_setup_ops has not been called > and dma_supported is only implemented by __dummy_dma_supported, returning 0. > > Bisecting finds the "bad" commit as > 1dccb598df549d892b6450c261da54cdd7af44b4 (inbetween 4.4-rc1 and 4.4-rc2) > --- a/arch/arm64/include/asm/dma-mapping.h > --- a/arch/arm64/mm/dma-mapping.c > > Previous to this commit, dma_ops = &swiotlb_dma_ops was done in arm64_dma_init > After this commit, the assignment is only done in arch_dma_setup_ops. This restriction was added on purpose and the arm64 __generic_dma_ops() now has a comment: /* * We expect no ISA devices, and all other DMA masters are expected to * have someone call arch_setup_dma_ops at device creation time. */ The commit above also describes why it is dangerous to assume a fallback to swiotlb ops. > We're not using any dwc3-<glue>.c wrapper here, but we've not needed it before this commit. Relevant ? > It might also be possible that we've messed up some KConfig that changed between versions ? > Or is this a bug that needs patching - in arm(64) dma or something different for dma setup in dwc3/host.c ? What I don't understand is why of_dma_configure() is not called for a device with compatible="synopsys,dwc3" in DT (IIUC, you said that you specify this in DT and of_platform_populate should do the right configuration). -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
