Re: [RFC v4] PCI: PTM Driver

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, May 03, 2016 at 05:02:45PM +0800, Yong, Jonathan wrote:
> On 04/29/2016 22:17, Bjorn Helgaas wrote:
> >On Tue, Apr 19, 2016 at 06:29:17AM +0000, Yong, Jonathan wrote:
> >>Hello LKML,
> >>
> >>This is a preliminary implementation of the PTM[1] support driver. This driver
> >>has only been tested against a virtual PCI bus since there are no known
> >>endpoints utilizing it yet.
> >
> >What sort of testing is this, exactly?  Is this using a software model
> >of devices that support PTM?
> >
> 
> We wrote another driver to fake the PCI config space with
> pci_scan_bus, with fake switches and fake devices. Convenient since
> the driver only deals with the config space.
> 
> >When will hardware that supports PTM be available to you for testing?
> >When will it be available on the market?
> >
> 
> I don't have any dates for when consumer endpoints will hit the
> market. PTM aware FPGA device models might come around Q3/Q4 this
> year, with exercisers around 2017.
> 
> >I'm trying to figure out whether there's any benefit to merging
> >something before it is useful to anybody.
> >
> 
> True it won't be useful to anybody until such a device is available.
> What is the general policy for future hardware standards?

I don't know if there is a real consensus about that.  In this case,
the feature is relatively simple (at least compared to, say ASPM), and
it's defined by a spec that's already been published, so I don't think
there's really much reason to wait.

I think the most expedient thing is to get it merged now so it'll be
easier to test and deploy it.

Bjorn