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From:   Rob Herring <robh+dt@kernel.org>
Date:   Fri, 17 Apr 2020 13:16:25 -0500
Message-ID: <CAL_JsqK9VmRomOnkVLQUOR9tHnh6phjjqXB=ERkjqhBw_wTVzg@mail.gmail.com>
Subject: Re: [PATCH v1] of: property: Don't retry device_link_add() upon failure
To:     Saravana Kannan <saravanak@google.com>
Cc:     Frank Rowand <frowand.list@gmail.com>,
        Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Android Kernel Team <kernel-team@android.com>,
        devicetree@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Thu, Apr 16, 2020 at 3:58 PM Saravana Kannan <saravanak@google.com> wrote:
>
> When of_link_to_phandle() was implemented initially, there was no way to
> tell if device_link_add() was failing because the supplier device hasn't
> been parsed yet, hasn't been added yet, the links were creating a cycle,
> etc. Some of these were transient errors that'd go away at a later
> point.
>
> However, with the current set of improved checks, if device_link_add()
> fails, it'll only be for permanent errors like cycles or out-of-memory
> errors.

What improved checks? The series from Nicolas?

Is there a dependency between this and Nicolas' series?

Should this go to stable?


>
> Also, with the addition of DL_FLAG_SYNC_STATE_ONLY flag [1] to device
> links, all the valid dependency cycles due to "proxy" device links
> (needed for correctness of sync_state() device callback) will never fail
> device_link_add() due to cycles.
>
> So, continuing to retry failing device links (by returning -EAGAIN) is
> no longer useful. At worst, it prevents platforms from setting
> fw_devlink=on (or better) because it prevents proper boot up. So, let's
> not do that anymore.
>
> [1] - https://lore.kernel.org/lkml/20191028220027.251605-1-saravanak@google.com/
> Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Saravana Kannan <saravanak@google.com>
> ---
>  drivers/of/property.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index 252e4f600155..ee1bc267f975 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -1074,7 +1074,7 @@ static int of_link_to_phandle(struct device *dev, struct device_node *sup_np,
>                 return -EAGAIN;
>         }
>         if (!device_link_add(dev, sup_dev, dl_flags))
> -               ret = -EAGAIN;
> +               ret = -EINVAL;
>         put_device(sup_dev);
>         return ret;
>  }
> --
> 2.26.1.301.g55bc3eb7cb9-goog
>