On Tue, Feb 11, 2025 at 12:38:59PM -0600, Bjorn Helgaas wrote: > On Tue, Feb 11, 2025 at 01:03:52PM -0500, Alyssa Rosenzweig wrote: > > From: Janne Grunau <j@xxxxxxxxxx> > > > > The iommu on Apple's M1 and M2 supports only a page size of 16kB and is > > mandatory for PCIe devices. Mismatched page sizes will render devices > > useless due to non-working DMA. While the iommu prints a warning in this > > scenario, it seems a common and hard to debug problem, so prevent it at > > build-time. > > Can we include a sample iommu warning here to help people debug this > problem? I don't remember and it might have changed in the meantime due to iommu subsystem changes. What currently happens is that apple_dart_attach_dev_identity() fails with -EINVAL. I can't say whether that results in a failure to probe now. I'll test and report back. Janne
