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

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Date:   Tue, 5 Dec 2017 15:56:55 +0100
From:   Richard Leitner <richard.leitner@...data.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Richard Leitner <dev@...l1n.net>, 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>
Subject: Re: [PATCH net-next v3 1/4] phylib: Add device reset delay support

Hi Geert,

On 12/05/2017 02:54 PM, Geert Uytterhoeven wrote:
> 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.

Ok. Thanks. That makes sense. I'll take it into account for v4.

> 
>> Signed-off-by: Richard Leitner <richard.leitner@...data.com>
> 
> Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
> 
> Although I have a few suggestions below:

Thank you for your review and suggestions (they make the code look way
more neater). I'll adapt v4 accordingly.

> 
>> --- 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);