On Fri, Apr 15, 2016 at 12:49:15PM +0300, Felipe Balbi wrote: > Catalin Marinas <catalin.marinas@xxxxxxx> writes: > > 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. > > */ > > how ? Usually by calling arch_setup_dma_ops(). > > 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). > > it works fine for dwc3 core, but dwc3 manually creates a device for the > XHCI core it has inside it. Ah, I think I get it know. We have something similar for pci_device_add() which calls arch_setup_dma_ops() (explicitly via pci_dma_configure()) since the PCI devices are probed at runtime, so we can't specify them in DT. The PCI device inherits some properties from the parent node. The issue with a default swiotlb is that it may not always be the right thing like the device being behind an IOMMU. -- 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
