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
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