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From: Srinath Mannam <srinath.mannam@broadcom.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: linux-pci@vger.kernel.org,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Sinan Kaya <okaya@codeaurora.org>,
	Rajat Jain <rajatja@google.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 1/2] PCI/ASPM: Disable ASPM L1.2 Substate if we don't have LTR
Date: Fri, 20 Apr 2018 14:22:06 +0530	[thread overview]
Message-ID: <CABe79T546trxQ2YSUj74SmW2qVUPkB1Mor2TP-K3SM0rerpogw@mail.gmail.com> (raw)
In-Reply-To: <152417192976.76853.5171081412139699180.stgit@bhelgaas-glaptop.roam.corp.google.com>

Hi Bjorn,

I have verified this patch, it works fine for me.

Thanks & Regards,
Srinath.

On Fri, Apr 20, 2018 at 2:35 AM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> From: Bjorn Helgaas <bhelgaas@google.com>
>
> When in the ASPM L1.0 state (but not the PCI-PM L1.0 state), the most
> recent LTR value and the LTR_L1.2_THRESHOLD determines whether the link
> enters the L1.2 substate.
>
> If we don't have LTR enabled, prevent the use of ASPM L1.2.
>
> PCI-PM L1.2 may still be used because it doesn't depend on
> LTR_L1.2_THRESHOLD (see PCIe r4.0, sec 5.5.1).
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> ---
>  drivers/pci/pcie/aspm.c |    9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index f76eb7704f64..c687c817b47d 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -400,6 +400,15 @@ static void pcie_get_aspm_reg(struct pci_dev *pdev,
>                 info->l1ss_cap = 0;
>                 return;
>         }
> +
> +       /*
> +        * If we don't have LTR for the entire path from the Root Complex
> +        * to this device, we can't use ASPM L1.2 because it relies on the
> +        * LTR_L1.2_THRESHOLD.  See PCIe r4.0, secs 5.5.4, 6.18.
> +        */
> +       if (!pdev->ltr_path)
> +               info->l1ss_cap &= ~PCI_L1SS_CAP_ASPM_L1_2;
> +
>         pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL1,
>                               &info->l1ss_ctl1);
>         pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL2,
>

  reply	other threads:[~2018-04-20  8:52 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-19 21:05 [PATCH v1 0/2] PCI/ASPM: Tighten up ASPM L1.2 and LTR usage 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 [this message]
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

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