On Wed, Jan 11, 2017 at 4:36 AM, Will Deacon <will.deacon@xxxxxxx> wrote: > On Tue, Jan 10, 2017 at 02:20:13PM -0500, Rob Clark wrote: >> On Tue, Jan 10, 2017 at 12:52 PM, Will Deacon <will.deacon@xxxxxxx> wrote: >> > On Fri, Jan 06, 2017 at 11:26:49AM -0500, Rob Clark wrote: >> >> Hmm, well we install the fault handler on the iommu_domain.. perhaps >> >> maybe a combo of dts property (or deciding based on more specific >> >> compat string), plus extra param passed in to >> >> iommu_set_fault_hander(). The dts property or compat string to >> >> indicate whether the iommu (and how it is wired up) can handle stalls, >> >> and enable_stall param when fault handler is registered to indicate >> >> whether the device itself can cope.. if either can't do stalling, then >> >> don't set CFCFG. >> > >> > I thought about this some more, and I think you're right. Having >> > iommu_set_fault_handler take a flags parameter indicating that, for example, >> > the fault handler can deal with paging, is all we need to implement the >> > per-master opt-in functionality for stalling faults. There's no real >> > requirement to standardise a generic firmware property for that (but >> > we still need *something* that says stalling is usable on the SMMU -- >> > perhaps just the compatible string is ok). >> >> btw, it occurred to me that maybe it should be flags param to >> iommu_attach_device() (just in case fault handler not installed?) >> otoh stalling without a fault handler is silly, but I guess we need it >> to infer whether stalling can be supported by other devices on same >> iommu.. tbh I'm on a bit shaky ground when it comes to multiple >> devices per iommu since the SoC's I'm familiar with do it the other >> way around. But I guess you have thought more about the multi-device >> case, so figured I should suggest it.. > > I don't think it works at attach time, because the stalling property belongs > to the domain, rather than the individual devices within it. Similarly, I > don't think we should allow this property to be toggled once devices have > been attached. > hmm, I was more thinking of cases where drivers for particular devices need some work (ie. like potentially disabling hw hang detect during faults).. I guess we could have three levels, that all have to be true in order to enable stall: smmu, domain (pass flags in to iommu_domain_alloc()??), and device (iommu_attach_device())? BR, -R -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
