On Thu, Dec 17, 2020 at 09:44:31AM +0100, Nicolas Saenz Julienne wrote: > On Thu, 2020-12-17 at 16:08 +0800, Peng Fan (OSS) wrote: > > From: Peng Fan <peng....@nxp.com> > > > > ZONE_DMA should not be disabled, otherwise arm64_dma_phys_limit is > > left uninitialized and cause swiotlb have IO TLB above 4GB which > > might crash some platforms
Actually, arm64_dma_phys_limit would be zero-initialised. The ARCH_LOW_ADDRESS_LIMIT becomes ~0UL, hence it covers the whole address space. > > Signed-off-by: Peng Fan <peng....@nxp.com> > > --- > > > > Not sure whether need to address code to initialize the variables or > > force select ZONE_DMA > > What is the cause for the swiotlb related crashes? I assume it's DMA into an > address too high for the bus, but it might be something else. I think that's the case, swiotlb is not within the low 32-bit of the address space. > I figure you have a setup with ZONE_DMA32, ZONE_NORMAL and !ZONE_DMA. > > First of all, I'd suggest you try arm64's defaults (all zones enabled), the > series I mention above should fix most of the issues we've had with > ZONE_DMA/ZONE_DMA32 in the past. We now parse DT/ACPI and only create two > distinct DMA zones if really needed. Otherwise ZONE_DMA spans the whole 32 bit > address space. > > That said, IMO we're not doing the right thing in the !ZONE_DMA && ZONE_DMA32 > case, and this should fix it (I didn't test it): > > - #define ARCH_LOW_ADDRESS_LIMIT (arm64_dma_phys_limit - 1) > + #define ARCH_LOW_ADDRESS_LIMIT (arm64_dma_phys_limit ? : > arm64_dma32_phys_limit) Does this limit need to be inclusive? -- Catalin