linux-kernel - Re: [PATCH v2] PCI: dwc: Wait for link up only if link is started

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Message-ID: <CAPOBaE4U4rCJ+4CcSoj597LsP-0ESBhiKKHz00bk+SvNHrOzKQ@mail.gmail.com>
Date:   Tue, 28 Feb 2023 14:04:30 -0800
From:   Han Jingoo <jingoohan1@...il.com>
To:     Sajid Dalvi <sdalvi@...gle.com>
Cc:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>, kernel-team@...roid.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: Re: [PATCH v2] PCI: dwc: Wait for link up only if link is started

On Mon, Feb 27, 2023, Sajid Dalvi <sdalvi@...gle.com> wrote:
>
> In dw_pcie_host_init() regardless of whether the link has been started
> or not, the code waits for the link to come up. Even in cases where
> start_link() is not defined the code ends up spinning in a loop for 1
> second. Since in some systems dw_pcie_host_init() gets called during
> probe, this one second loop for each pcie interface instance ends up
> extending the boot time.
>
> Call trace when start_link() is not defined:
> dw_pcie_wait_for_link << spins in a loop for 1 second
> dw_pcie_host_init
>
> Signed-off-by: Sajid Dalvi <sdalvi@...gle.com>

(CC'ed Krzysztof Kozlowski)

Acked-by: Jingoo Han <jingoohan1@...il.com>

It looks good to me. I also checked the previous thread.
I agree with Krzysztof's opinion that we should include
only hardware-related features into DT.
Thank you.

Best regards,
Jingoo Han

> ---
>  drivers/pci/controller/dwc/pcie-designware-host.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 9952057c8819..9709f69f173e 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -489,10 +489,10 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
>                 ret = dw_pcie_start_link(pci);
>                 if (ret)
>                         goto err_remove_edma;
> -       }
>
> -       /* Ignore errors, the link may come up later */
> -       dw_pcie_wait_for_link(pci);
> +               /* Ignore errors, the link may come up later */
> +               dw_pcie_wait_for_link(pci);
> +       }
>
>         bridge->sysdata = pp;
>
> --
> 2.39.2.722.g9855ee24e9-goog
>