On Tue, Apr 09, 2019 at 05:52:39PM +0100, Jean-Philippe Brucker wrote: > Root complex node in IORT has a bit telling whether it supports ATS or > not. Store this bit in the IOMMU fwspec when setting up a device, so it > can be accessed later by an IOMMU driver. > > Use the negative version (NO_ATS) at the moment because it's not clear > if/how the bit needs to be integrated in other firmware descriptions. The > SMMU has a feature bit telling if it supports ATS, which might be > sufficient in most systems for deciding whether or not we should enable > the ATS capability in endpoints.
Hmm, the SMMUv3 architecture manual is pretty explicit about this: | It [SMMU_IDR0.ATS] does not guarantee that client devices and intermediate | components also support ATS and this must be determined separately. so we may need to extend the PCI bindings to describe this. I think the negative logic is likely to get in the way if that's the case. > Signed-off-by: Jean-Philippe Brucker <[email protected]> > --- > drivers/acpi/arm64/iort.c | 11 +++++++++++ > include/linux/iommu.h | 4 ++++ > 2 files changed, 15 insertions(+) > > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c > index e48894e002ba..7f2c1c9c6b38 100644 > --- a/drivers/acpi/arm64/iort.c > +++ b/drivers/acpi/arm64/iort.c > @@ -1028,6 +1028,14 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, > u64 *dma_size) > dev_dbg(dev, "dma_pfn_offset(%#08llx)\n", offset); > } > > +static bool iort_pci_rc_supports_ats(struct acpi_iort_node *node) > +{ > + struct acpi_iort_root_complex *pci_rc; > + > + pci_rc = (struct acpi_iort_root_complex *)node->node_data; > + return pci_rc->ats_attribute & ACPI_IORT_ATS_SUPPORTED; > +} Do we need to worry about the "noats" command-line option here? It feels like we should be checking with the PCI subsystem before telling the SMMU we're good to go. I'll need Lorenzo's ack on this. Will _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
