On Fri, Dec 04, 2015 at 01:33:30PM -0600, Jay Cornwall wrote: > On 2015-12-04 12:25, Bjorn Helgaas wrote: > >On Thu, Sep 24, 2015 at 10:59:50AM -0500, Jay Cornwall wrote: > >>The PCIe 3.0 AtomicOp (6.15) feature allows atomic transctions > >>to be requested > >>by, routed through and completed by PCIe components. Routing and > >>completion > >>do not require software support. Component support for each is > >>detectable via > >>the DEVCAP2 register. > >> > >>AtomicOp requests are permitted only if a component's > >>DEVCTL2.ATOMICOP_REQUESTER_ENABLE field is set. This capability > >>cannot be > >>detected but is a no-op if set on a component with no support. > >>These requests > >>can only be serviced if the upstream components support AtomicOp > >>completion > >>and/or routing to a component which does. > >> > >>A concrete example is the AMD Fiji-class GPU, which is specified > >>to support > >>AtomicOp requests, routed through a PLX 8747 switch (advertising > >>AtomicOp > >>routing) to a Haswell host bridge (advertising AtomicOp > >>completion support). > >>When AtomicOp requests are disabled the GPU logs attempts to > >>initiate requests > >>to an MMIO register for debugging. > >> > >>Add pci_enable_atomic_request for per-device control over > >>AtomicOp requests. > >>Upstream bridges are checked for AtomicOp routing capability and > >>the call > >>fails if any lack this capability. The root port is checked for > >>AtomicOp > >>completion capabilities and the call fails if it does not support any. > >>Routes to other PCIe components are not checked for AtomicOp > >>routing and > >>completion capabilities. > >> > >>v2: Check for AtomicOp route to root port with AtomicOp completion > >>v3: Style fixes > >> > >>Signed-off-by: Jay Cornwall <jay@xxxxxxxxxxxx> > > > >Hi Jay, > > > >Is there a user for this new functionality? I don't like to add things > >that have no apparent user. > > > >Bjorn > > The client for this code is scheduled to be upstreamed in > drm/amdgpu, but we have some internal restructuring to complete > before a patchset will be available. > > If you'd prefer, I can resubmit this patch as part of that series > when it is ready. Yeah, that'd be great, why don't we do that. Thanks! Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
