LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Bjorn Helgaas <helgaas@kernel.org>
To: linux-pci@vger.kernel.org
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Sinan Kaya <okaya@codeaurora.org>,
	Rajat Jain <rajatja@google.com>,
	Srinath Mannam <srinath.mannam@broadcom.com>,
	Ray Jui <ray.jui@broadcom.com>,
	Keith Busch <keith.busch@intel.com>,
	linux-acpi@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 0/2] PCI/ASPM: Tighten up ASPM L1.2 and LTR usage
Date: Mon, 30 Apr 2018 16:02:56 -0500	[thread overview]
Message-ID: <20180430210256.GE95643@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <152417080402.76853.4258398181136860884.stgit@bhelgaas-glaptop.roam.corp.google.com>

On Thu, Apr 19, 2018 at 04:05:19PM -0500, Bjorn Helgaas wrote:
> The ASPM L1.2 substate depends on LTR information.  Per the PCI
> Firmware spec, the OS is supposed to negotiate with the platform for
> control of the LTR feature, but previously we didn't do that.
> 
> In addition, we must not enable LTR in an endpoint unless the Root
> Complex and all intermediate switches also support LTR.  We already
> took care of that in pci_configure_ltr(), but we didn't ensure that
> LTR was enabled before allowing ASPM L1.2 to be enabled.
> 
> These patches fix both of these issues.  Or rather, they *should* fix
> them.  I don't have hardware to test them, so any help with testing
> would be appreciated.
> 
> I think the most likely issue would be a platform where the hardware
> supports LTR and the ASPM L1.2 substate, but the BIOS doesn't support
> LTR in _OSC.  In that case, we previously could have enabled ASPM L1.2
> (though it probably wouldn't work correctly), and after these patches,
> we should not enable ASPM L1.2.
> 
> You can look for issues by comparing dmesg and "lspci -vv" output
> before and after these patches.
> 
> It would also be interesting to collect an acpidump from platforms
> that support LTR, even if there's no endpoint that supports ASPM L1.2.
> The acpidump should show that _OSC supports LTR.
> 
> I included some NVMe folks because these were motivated by Srinath's
> recent report of LTR and ASPM issues with a Samsung NVMe SSD
> Controller SM961/PM961 device, so this is sort of FYI in case you see
> similar issues or are in a position to test these.
> 
> ---
> 
> Bjorn Helgaas (2):
>       PCI/ASPM: Disable ASPM L1.2 Substate if we don't have LTR
>       PCI/ACPI: Request LTR control from platform before using it
> 
> 
>  drivers/acpi/pci_root.c |    7 +++++++
>  drivers/pci/pcie/aspm.c |    9 +++++++++
>  drivers/pci/probe.c     |    5 +++++
>  include/linux/acpi.h    |    3 ++-
>  include/linux/pci.h     |    1 +
>  5 files changed, 24 insertions(+), 1 deletion(-)

Applied to pci/aspm for v4.18 with Rafael's reviewed-by and Srinath's
tested-by (on first patch).

      parent reply	other threads:[~2018-04-30 21:03 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-19 21:05 Bjorn Helgaas
2018-04-19 21:05 ` [PATCH v1 1/2] PCI/ASPM: Disable ASPM L1.2 Substate if we don't have LTR Bjorn Helgaas
2018-04-20  8:52   ` Srinath Mannam
2018-04-19 21:05 ` [PATCH v1 2/2] PCI/ACPI: Request LTR control from platform before using it Bjorn Helgaas
2018-04-23  7:56 ` [PATCH v1 0/2] PCI/ASPM: Tighten up ASPM L1.2 and LTR usage Rafael J. Wysocki
2018-04-30 21:02 ` Bjorn Helgaas [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180430210256.GE95643@bhelgaas-glaptop.roam.corp.google.com \
    --to=helgaas@kernel.org \
    --cc=keith.busch@intel.com \
    --cc=linux-acpi@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-nvme@lists.infradead.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=okaya@codeaurora.org \
    --cc=rajatja@google.com \
    --cc=ray.jui@broadcom.com \
    --cc=rjw@rjwysocki.net \
    --cc=srinath.mannam@broadcom.com \
    --subject='Re: [PATCH v1 0/2] PCI/ASPM: Tighten up ASPM L1.2 and LTR usage' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).