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From: Ian Kumlien <ian.kumlien@gmail.com>
To: linux-pci@vger.kernel.org
Subject: Re: [PATCH] Use maximum latency when determining L1 ASPM
Date: Mon, 27 Jul 2020 23:17:35 +0200
Message-ID: <CAA85sZv8y9WLwtqimkVw9dFWubYiV0=HmZQ49cKCTJYm8f+k2Q@mail.gmail.com> (raw)
In-Reply-To: <20200726220653.635852-2-ian.kumlien@gmail.com>

Sorry, the changelog is broken -- Will resend...

That'll teach me for thinking after working out... =)

On Mon, Jul 27, 2020 at 12:07 AM Ian Kumlien <ian.kumlien@gmail.com> wrote:
>
> The current solution verifies per "hop" but doesn't
> check the maximum latency, instead it checks the
> current "hops" max latency for upstream and downstrea,
>
> This would work if all "hops" have the same latency, but:
>
> root -> a -> b -> c -> endpoint
>
> If c or b has the higest latency, it might not register
>
> Fix this by maintaining a maximum value for comparison
>
> Signed-off-by: Ian Kumlien <ian.kumlien@gmail.com>
> ---
>  drivers/pci/pcie/aspm.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index b17e5ffd31b1..bd53fba7f382 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -434,7 +434,7 @@ static void pcie_get_aspm_reg(struct pci_dev *pdev,
>
>  static void pcie_aspm_check_latency(struct pci_dev *endpoint)
>  {
> -       u32 latency, l1_switch_latency = 0;
> +       u32 latency, l1_max_latency = 0, l1_switch_latency = 0;
>         struct aspm_latency *acceptable;
>         struct pcie_link_state *link;
>
> @@ -470,8 +470,9 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
>                  * substate latencies (and hence do not do any check).
>                  */
>                 latency = max_t(u32, link->latency_up.l1, link->latency_dw.l1);
> +               l1_max_latency = max_t(u32, latency, l1_max_latency);
>                 if ((link->aspm_capable & ASPM_STATE_L1) &&
> -                   (latency + l1_switch_latency > acceptable->l1))
> +                   (l1_max_latency + l1_switch_latency > acceptable->l1))
>                         link->aspm_capable &= ~ASPM_STATE_L1;
>                 l1_switch_latency += 1000;
>
> --
> 2.27.0
>

  reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-26 22:06 Ian Kumlien
2020-07-26 22:06 ` Ian Kumlien
2020-07-27 21:17   ` Ian Kumlien [this message]
2020-07-27 21:30 Ian Kumlien
2020-07-29 22:27 ` Bjorn Helgaas
2020-07-29 22:43   ` Ian Kumlien

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