netdev - Re: [PATCH net-next v3 1/4] phylib: Add device reset delay support

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Message-ID: <CAMuHMdX70yuEfoDL+Y4TZ-6zjyW9BqvKOU6UxbHTKGNcgfGrow@mail.gmail.com>
Date:   Tue, 5 Dec 2017 14:54:05 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Richard Leitner <dev@...l1n.net>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Fugang Duan <fugang.duan@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Frank Rowand <frowand.list@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        Baruch Siach <baruch@...s.co.il>,
        David Wu <david.wu@...k-chips.com>, lukma@...x.de,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Richard Leitner <richard.leitner@...data.com>
Subject: Re: [PATCH net-next v3 1/4] phylib: Add device reset delay support

Hi Richard,

On Tue, Dec 5, 2017 at 2:25 PM, Richard Leitner <dev@...l1n.net> wrote:
> From: Richard Leitner <richard.leitner@...data.com>
>
> Some PHYs need a minimum time after the reset gpio was asserted and/or
> deasserted. To ensure we meet these timing requirements add two new
> optional devicetree parameters for the phy: reset-delay-us and
> reset-post-delay-us.

Thanks for your patch!

> This patch depends on the "phylib: Add device reset GPIO support" patch
> submitted by Geert Uytterhoeven/Sergei Shtylyov, see:
>         https://patchwork.kernel.org/patch/10090149/

The above paragraph belongs under the "---" line below, as it is not intended
to be preserved in the eternal git history.

> Signed-off-by: Richard Leitner <richard.leitner@...data.com>

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

Although I have a few suggestions below:

> --- a/drivers/net/phy/mdio_device.c
> +++ b/drivers/net/phy/mdio_device.c
> @@ -118,8 +119,16 @@ EXPORT_SYMBOL(mdio_device_remove);
>
>  void mdio_device_reset(struct mdio_device *mdiodev, int value)
>  {
> -       if (mdiodev->reset)
> -               gpiod_set_value(mdiodev->reset, value);
> +       if (!mdiodev->reset)
> +               return;
> +
> +       gpiod_set_value(mdiodev->reset, value);
> +
> +       if (value && mdiodev->reset_delay)
> +               usleep_range(mdiodev->reset_delay, mdiodev->reset_delay + 100);
> +       else if (!value && mdiodev->reset_post_delay)
> +               usleep_range(mdiodev->reset_post_delay,
> +                            mdiodev->reset_post_delay + 100);

I think this can be written simpler using e.g.:

        unsigned int delay;

        ...
        delay = value ? mdiodev->reset_delay : mdiodev->reset_post_delay;
        if (delay)
                usleep_range(delay, delay + 100);

Perhaps the range extension should be relative, e.g.
"delay + min(delay / 10, 100)"?

> --- a/drivers/of/of_mdio.c
> +++ b/drivers/of/of_mdio.c
> @@ -77,6 +77,14 @@ static int of_mdiobus_register_phy(struct mii_bus *mdio,
>         if (of_property_read_bool(child, "broken-turn-around"))
>                 mdio->phy_ignore_ta_mask |= 1 << addr;
>
> +       if (of_property_read_u32(child, "reset-delay-us",
> +                                &phy->mdio.reset_delay))
> +               phy->mdio.reset_delay = 0;
> +
> +       if (of_property_read_u32(child, "reset-post-delay-us",
> +                                &phy->mdio.reset_post_delay))
> +               phy->mdio.reset_post_delay = 0;

If of_property_read_u32() fails, it doesn't write to its output parameter.
As the structure should be zeroed during allocation, you can just write:

        of_property_read_u32(child, "reset-delay-us", &phy->mdio.reset_delay);
        of_property_read_u32(child, "reset-post-delay-us",
                             &phy->mdio.reset_post_delay);

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds