netdev - Re: [PATCH] phy: add support for a reset-gpio specification

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Date:	Thu, 12 May 2016 18:14:11 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Roger Quadros <rogerq@...com>
Cc:	Nishanth Menon <nm@...com>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org,
	Florian Fainelli <f.fainelli@...il.com>, kernel@...gutronix.de,
	"Andrew F . Davis" <afd@...com>, Sekhar Nori <nsekhar@...com>,
	Suman Anna <s-anna@...com>
Subject: Re: [PATCH] phy: add support for a reset-gpio specification

Hello,

On Thu, May 12, 2016 at 05:16:56PM +0300, Roger Quadros wrote:
> On 12/05/16 17:02, Roger Quadros wrote:
> > On 12/05/16 16:50, Nishanth Menon wrote:
> >> On 05/12/2016 05:00 AM, Uwe Kleine-König wrote:
> >>> The framework only asserts (for now) that the reset gpio is not active.
> >>>
> >>> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> >>> ---
> >>>  Documentation/devicetree/bindings/net/phy.txt | 3 +++
> >>>  drivers/net/phy/phy_device.c                  | 8 ++++++++
> >>>  2 files changed, 11 insertions(+)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/net/phy.txt b/Documentation/devicetree/bindings/net/phy.txt
> >>> index bc1c3c8bf8fa..c00a9a894547 100644
> >>> --- a/Documentation/devicetree/bindings/net/phy.txt
> >>> +++ b/Documentation/devicetree/bindings/net/phy.txt
> >>> @@ -35,6 +35,8 @@ Optional Properties:
> >>>  - broken-turn-around: If set, indicates the PHY device does not correctly
> >>>    release the turn around line low at the end of a MDIO transaction.
> >>>  
> >>> +- reset-gpios: Reference to a GPIO used to reset the phy.
> >>> +
> >>>  Example:
> >>>  
> >>>  ethernet-phy@0 {
> >>> @@ -42,4 +44,5 @@ ethernet-phy@0 {
> >>>  	interrupt-parent = <40000>;
> >>>  	interrupts = <35 1>;
> >>>  	reg = <0>;
> >>> +	reset-gpios = <&gpio1 17 GPIO_ACTIVE_LOW>;
> >>>  };
> >>> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> >>> index e551f3a89cfd..7d666ab47271 100644
> >>> --- a/drivers/net/phy/phy_device.c
> >>> +++ b/drivers/net/phy/phy_device.c
> >>> @@ -34,6 +34,7 @@
> >>>  #include <linux/io.h>
> >>>  #include <linux/uaccess.h>
> >>>  #include <linux/of.h>
> >>> +#include <linux/gpio/consumer.h>
> >>>  
> >>>  #include <asm/irq.h>
> >>>  
> >>> @@ -1569,9 +1570,16 @@ static int phy_probe(struct device *dev)
> >>>  	struct device_driver *drv = phydev->mdio.dev.driver;
> >>>  	struct phy_driver *phydrv = to_phy_driver(drv);
> >>>  	int err = 0;
> >>> +	struct gpio_descs *reset_gpios;
> >>>  
> >>>  	phydev->drv = phydrv;
> >>>  
> >>> +	/* take phy out of reset */
> >>> +	reset_gpios = devm_gpiod_get_array_optional(dev, "reset",
> >>> +						    GPIOD_OUT_LOW);
> >>> +	if (IS_ERR(reset_gpios))
> >>> +		return PTR_ERR(reset_gpios);
> >>> +
> >>>  	/* Disable the interrupt if the PHY doesn't support it
> >>>  	 * but the interrupt is still a valid one
> >>>  	 */
> >>>
> >>
> >> This looks like the right approach to me at least: I see that TI EVMs
> >> will also benefit with this approach.
> >>
> > 
> > Agreed. Although on some of our boards we actually need a RESET pulse
> > to get the PHY in a sane state. I can send a patch on top for that.
> > 
> 
> I think I replied too early. Will phy_probe() be called at all if the
> PHY is not detected on the MDIO bus?
> If not then this approach is not sufficient for some of the TI boards.
> e.g. am57xx-idk.
> I think the reset needs to be done at MDIO bus level before it enumerates
> the PHYs so that we know the PHY is in an enumerable state.
I have this in the device tree:

&davinci_mdio {
        pinctrl-names = "default", "sleep";
        pinctrl-0 = <&davinci_mdio_default>;
        pinctrl-1 = <&davinci_mdio_sleep>;
        status = "okay";

        phy0: ethernet-phy@0 {
                compatible = "ethernet-phy-id2000.a212", "ethernet-phy-ieee802.3-c22";
                reg = <0>;

                interrupt-parent = <&gpio2>;
                interrupts = <2 8>;

                pinctrl-names = "default";
                pinctrl-0 = <&phy0_pins>;

                reset-gpios = <&gpio2 9 GPIO_ACTIVE_LOW>;
        };

        phy1: ethernet-phy@2 {
                compatible = "ethernet-phy-id2000.a212", "ethernet-phy-ieee802.3-c22";
                reg = <2>;

                interrupt-parent = <&gpio0>;
                interrupts = <2 8>;

                pinctrl-names = "default";
                pinctrl-0 = <&phy1_pins>;

                reset-gpios = <&gpio2 11 GPIO_ACTIVE_LOW>;
        };
};

With the phy id values specified in the compatible the mdio bus is only
accessed when the reset pin was handled.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |