From: Bjorn Helgaas <helgaas@kernel.org>
To: Jay Cornwall <jay@jcornwall.me>
Cc: linux-pci@vger.kernel.org
Subject: Re: [PATCH v3] PCI: Add pci_enable_atomic_request
Date: Mon, 7 Dec 2015 10:23:51 -0600 [thread overview]
Message-ID: <20151207162351.GH7994@localhost> (raw)
In-Reply-To: <c7259e37a065e8c7d386c806f521c46d@jcornwall.me>
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@jcornwall.me>
> >
> >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
next prev parent reply other threads:[~2015-12-07 16:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-24 15:59 [PATCH v3] PCI: Add pci_enable_atomic_request Jay Cornwall
2015-12-04 18:25 ` Bjorn Helgaas
2015-12-04 19:33 ` Jay Cornwall
2015-12-07 16:23 ` Bjorn Helgaas [this message]
2016-03-28 20:10 ` Jay Cornwall
2016-05-05 15:40 ` Jay Cornwall
2016-05-06 15:48 ` Bjorn Helgaas
2016-05-06 15:48 ` Bjorn Helgaas
2016-05-16 17:23 ` Jay Cornwall
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