linux-kernel - Re: [PATCH] ARM: dts: add phy-reset property for rk3066a-rayeager emac

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Date:   Thu, 9 Nov 2017 10:20:57 +0200
From:   Roger Quadros <rogerq@...com>
To:     Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
        Chris Zhong <zyw@...k-chips.com>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
CC:     <heiko@...ech.de>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-rockchip@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH] ARM: dts: add phy-reset property for rk3066a-rayeager
 emac

Hi,

On 07/11/17 09:54, Vladimir Zapolskiy wrote:
> Hello Chris,
> 
> On 11/07/2017 04:49 AM, Chris Zhong wrote:
>> The ethernet phy of rk3066a-rayeager has a reset pin, it controlled by
>> GPIO1_D6, this pin should be pull down then pull up to reset the phy.
>> Add a phy-reset property in emac, make the phy can be reset when emac
>> power on.
> 
> for PHY reset there are properties 'reset-gpios' and 'reset-delay-us',
> please reference to Documentation/devicetree/bindings/net/mdio.txt
> 
> Can you try to reuse them instead of adding new custom properties?
> 
> As a side question, which is mainly addressed to Sergei and Roger,
> I don't quite understand why PHY properties were initially added to
> MAC/MDIO bus device tree nodes, in my opinion they must be moved under
> PHY device tree nodes.

The PHY reset *has* to be performed at the MDIO bus driver level so that they
can be pin-strap configured correctly and be detected during MDIO bus scan.

- We have boards where PHYs won't be detected if RESET is not done before the scan. (due to invalid h/w pin-strapping config)
- We have boards where a single GPIO line controls reset of all PHYs on the bus.

Due to these reasons the RESET control lies with the MDIO bus driver.

> 
> --
> With best wishes,
> Vladimir
> 
>>
>> Signed-off-by: Chris Zhong <zyw@...k-chips.com>
>> ---
>>
>>  arch/arm/boot/dts/rk3066a-rayeager.dts | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/arm/boot/dts/rk3066a-rayeager.dts b/arch/arm/boot/dts/rk3066a-rayeager.dts
>> index 570157f..6064a0a 100644
>> --- a/arch/arm/boot/dts/rk3066a-rayeager.dts
>> +++ b/arch/arm/boot/dts/rk3066a-rayeager.dts
>> @@ -173,6 +173,8 @@
>>  	pinctrl-0 = <&emac_xfer>, <&emac_mdio>, <&rmii_rst>;
>>  	phy = <&phy0>;
>>  	phy-supply = <&vcc_rmii>;
>> +	phy-reset-gpios = <&gpio1 RK_PD6 GPIO_ACTIVE_LOW>; /* PHY_RST */
>> +	phy-reset-duration = <10>; /* millisecond */
>>  	status = "okay";
>>  
>>  	phy0: ethernet-phy@0 {
>>

-- 
cheers,
-roger

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