netdev - Re: [PATCH v4.1] phylib: Add device reset GPIO support

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Message-ID: <69fe9a6d-4039-6f80-b80d-7dc0de31e5bf@cogentembedded.com>
Date:   Thu, 7 Dec 2017 20:20:05 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>,
        "David S . Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Simon Horman <horms@...ge.net.au>,
        Magnus Damm <magnus.damm@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Richard Leitner <richard.leitner@...data.com>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4.1] phylib: Add device reset GPIO support

Hello!

On 12/04/2017 03:35 PM, Geert Uytterhoeven wrote:

> From: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
> 
> The PHY devices sometimes do have their reset signal (maybe even power
> supply?) tied to some GPIO and sometimes it also does happen that a boot
> loader does not leave it deasserted. So far this issue has been attacked
> from (as I believe) a wrong angle: by teaching the MAC driver to manipulate
> the GPIO in question; that solution, when applied to the device trees, led
> to adding the PHY reset GPIO properties to the MAC device node, with one
> exception: Cadence MACB driver which could handle the "reset-gpios" prop
> in a PHY device subnode. I believe that the correct approach is to teach
> the 'phylib' to get the MDIO device reset GPIO from the device tree node
> corresponding to this device -- which this patch is doing...
> 
> Note that I had to modify the AT803x PHY driver as it would stop working
> otherwise -- it made use of the reset GPIO for its own purposes...
> 
> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
> Acked-by: Rob Herring <robh@...nel.org>
> [geert: Propagate actual errors from fwnode_get_named_gpiod()]
> [geert: Avoid destroying initial setup]
> [geert: Consolidate GPIO descriptor acquiring code]
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
[...]
> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
> index 2df7b62c1a36811e..8f8b7747c54bc478 100644
> --- a/drivers/net/phy/mdio_bus.c
> +++ b/drivers/net/phy/mdio_bus.c
[...]
> @@ -48,9 +49,26 @@
>   
>   int mdiobus_register_device(struct mdio_device *mdiodev)
>   {
> +	struct gpio_desc *gpiod = NULL;
> +
>   	if (mdiodev->bus->mdio_map[mdiodev->addr])
>   		return -EBUSY;
>   
> +	/* Deassert the optional reset signal */

    Umm, but why deassert it here for such a short time?

> +	if (mdiodev->dev.of_node)
> +		gpiod = fwnode_get_named_gpiod(&mdiodev->dev.of_node->fwnode,
> +					       "reset-gpios", 0, GPIOD_OUT_LOW,
> +					       "PHY reset");
> +	if (PTR_ERR(gpiod) == -ENOENT)
> +		gpiod = NULL;
> +	else if (IS_ERR(gpiod))
> +		return PTR_ERR(gpiod);

    Hm, returning on error with reset deasserted?

> +
> +	mdiodev->reset = gpiod;
> +
> +	/* Assert the reset signal again */
> +	mdio_device_reset(mdiodev, 1);
> +
>   	mdiodev->bus->mdio_map[mdiodev->addr] = mdiodev;
>   
>   	return 0;
[...]

MBR, Sergei