Re: [PATCH v6 0/3] PCI: Precision Time Measurement support

From	Bjorn Helgaas <helgaas@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v6 0/3] PCI: Precision Time Measurement support
Date	2016-08-15 21:00 +0200
Message-ID	<s6vh7-LT-1@gated-at.bofh.it> (permalink)
References	<rJFpg-22H-7@gated-at.bofh.it> <rWKAN-KV-3@gated-at.bofh.it> <rWMVY-22W-21@gated-at.bofh.it>
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On Wed, Jul 20, 2016 at 07:49:21AM +0800, Yong, Jonathan wrote:
> On 07/20/2016 05:19, Bjorn Helgaas wrote:
> > On Mon, Jun 13, 2016 at 02:05:26PM -0500, Bjorn Helgaas wrote:
> >> This is a slightly different proposal for the PTM support Jonathan
> >> proposed here:
> >>
> >>   http://lkml.kernel.org/r/1462956446-27361-2-git-send-email-jonathan.yong@intel.com
> >>
> >> I split this into three pieces mostly for ease in reviewing.  They
> >> could all be squashed:
> >>
> >>   - Enable PTM in root ports and switches automatically at boot
> >>   - Enable PTM in endpoints when requested by driver
> >>   - Add clock granularity information
> >>
> >> I have some open questions about how PTM works on Root Complex
> >> Integrated Endpoints and whether we should enable it automatically
> >> even without a driver request.  And I probably left out some details
> >> of the clock granularity computation, so treat this as more of an RFC
> >> than anything.
> >>
> > 
> > Jonathan, any comments?
> > 
> 
> I don't have any new information on how to configure integrated endpoints.
> 
> This line:
> ctrl = PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT;
> 
> should also set the responder capable bit (7.32.2):
> 	If PTM Root Capable is Set, this bit must be Set to 1b.

The PTM Responder Capable bit (bit 1 in Table 7-145) is a HwInit bit
in the PTM Capability register, so it's read-only from the kernel's
perspective.

The line you mention ("ctrl = PCI_PTM_CTRL_ENABLE | PCI_PTM_CTRL_ROOT")
is turning on bits in the PTM Control register, not the Capability
register.

Bjorn

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Re: [PATCH v6 0/3] PCI: Precision Time Measurement support Bjorn Helgaas <helgaas@kernel.org> - 2016-08-15 21:00 +0200
  Re: [PATCH v6 0/3] PCI: Precision Time Measurement support "Yong, Jonathan" <jonathan.yong@intel.com> - 2016-08-16 03:30 +0200

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