From: Bjorn Helgaas <helgaas@kernel.org>
To: Sinan Kaya <okaya@kernel.org>
Cc: Rajat Jain <rajatja@google.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Keith Busch <keith.busch@intel.com>,
Vidya Sagar <vidyas@nvidia.com>,
Philippe Ombredanne <pombredanne@nexb.com>,
Kees Cook <keescook@chromium.org>,
"Gustavo A. R. Silva" <garsilva@embeddedor.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Sinan Kaya <okaya@codeaurora.org>,
Frederick Lawler <fred@fredlawl.com>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
mayurkumar.patel@intel.com, rajatxjain@gmail.com,
Richard Hughes <rhughes@redhat.com>,
Carlos Garnacho <cgarnach@redhat.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Pali Rohar <pali.rohar@gmail.com>, Takashi Iwai <tiwai@suse.de>,
Andy Whitcroft <apw@canonical.com>,
Colin Ian King <colin.king@canonical.com>
Subject: Re: [PATCH v2] pci/aspm: Remove CONFIG_PCIEASPM_DEBUG
Date: Mon, 30 Jul 2018 09:14:28 -0500 [thread overview]
Message-ID: <20180730141428.GK173328@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <5a102163-73bc-c596-8266-186e222e7ceb@kernel.org>
On Sat, Jul 28, 2018 at 05:16:13PM -0700, Sinan Kaya wrote:
> On 7/27/2018 1:26 PM, Bjorn Helgaas wrote:
> > - A link can lead to a multi-function device, and the spec allows
> > those functions to have different ASPM settings (see PCIe r4.0,
> > sec 5.4.1). With the sysfs files at the upstream end of the link,
> > we have no way to configure those functions individually.
>
> Even though we can set them individually, there is only one PCIe link
> for single function as well as multi-function devices.
>
> It would be a user mistake to allow individual PCIe functions with
> different ASPM policies. (maybe, we should enforce it if we are not
> doing it already).
It's true that multi-function devices share a single PCIe link.
However, the end of sec 5.4.1 does make it clear that the functions
need not have the same ASPM configuration, and it gives rules for how
those different settings should affect the shared link. Since it
mentions different ASPM Control fields for the different functions, I
assume the policy combining those per-function settings into the
single link behavior must be implemented in the hardware.
Obviously we don't support per-function ASPM settings today. I don't
know whether there's any value in supporting them or not, but putting
the control files at the upstream end basically precludes us from ever
supporting them.
Bjorn
next prev parent reply other threads:[~2018-07-30 14:14 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-08 23:01 [PATCH] pci/aspm: Remove CONFIG_PCIEASPM_DEBUG Rajat Jain
2018-05-09 6:46 ` okaya
2018-05-09 9:43 ` kbuild test robot
2018-05-10 23:34 ` [PATCH] PM / s2idle: Clear the events_check_enabled flag Rajat Jain
2018-05-10 23:36 ` Rajat Jain
2018-05-10 23:39 ` [PATCH v2] pci/aspm: Remove CONFIG_PCIEASPM_DEBUG Rajat Jain
2018-06-05 22:15 ` Rajat Jain
2018-06-09 23:49 ` Sinan Kaya
2018-06-29 23:27 ` Bjorn Helgaas
2018-07-27 20:26 ` Bjorn Helgaas
2018-07-27 21:03 ` Takashi Iwai
2018-07-29 0:16 ` Sinan Kaya
2018-07-30 14:14 ` Bjorn Helgaas [this message]
2018-07-30 16:08 ` Sinan Kaya
2018-07-30 8:32 ` Lukas Wunner
2018-07-30 17:26 ` Bjorn Helgaas
2018-07-30 16:18 ` Rajat Jain
2018-07-31 8:13 ` Pali Rohár
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