linux-kernel - Re: [PATCH 4/8] arm64: dts: imx8mm-kontron: Fix reg_rst_eth2 and reg_vdd

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Message-ID: <725cc24e-f264-60ea-e30c-c50a61f7fe88@kontron.de>
Date:   Tue, 5 Oct 2021 19:06:57 +0200
From:   Frieder Schrempf <frieder.schrempf@...tron.de>
To:     Shawn Guo <shawnguo@...nel.org>, Frieder Schrempf <frieder@...s.de>
Cc:     devicetree@...r.kernel.org, Krzysztof Kozlowski <krzk@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>, stable@...r.kernel.org,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>
Subject: Re: [PATCH 4/8] arm64: dts: imx8mm-kontron: Fix reg_rst_eth2 and
 reg_vdd_5v regulators

On 05.10.21 09:09, Shawn Guo wrote:
> On Thu, Sep 30, 2021 at 05:56:27PM +0200, Frieder Schrempf wrote:
>> From: Frieder Schrempf <frieder.schrempf@...tron.de>
>>
>> The regulator reg_vdd_5v represents the fixed 5V supply on the board which
>> can't be switched off. Mark it as always-on.
>>
>> The regulator reg_rst_eth2 should keep the reset signal of the USB ethernet
>> adapter deassertet anytime. Fix the polarity and mark it as always-on.
> 
> It seems to be wrong from the beginning that the reset is modelled by a
> regulator.

Right, but at least at the time when I upstreamed this, there was no way
to pass the reset GPIO to a USB device driver and using a regulator
seems to be an accepted workaround as far as I understand.

> 
>>
>> Fixes: 21c4f45b335f ("arm64: dts: Add the Kontron i.MX8M Mini SoMs and baseboards")
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Frieder Schrempf <frieder.schrempf@...tron.de>
>> ---
>>  arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts b/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts
>> index 62ba3bd08a0c..f2c8ccefd1bf 100644
>> --- a/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts
>> +++ b/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-s.dts
>> @@ -70,7 +70,9 @@ reg_rst_eth2: regulator-rst-eth2 {
>>  		regulator-name = "rst-usb-eth2";
>>  		pinctrl-names = "default";
>>  		pinctrl-0 = <&pinctrl_usb_eth2>;
>> -		gpio = <&gpio3 2 GPIO_ACTIVE_LOW>;
>> +		gpio = <&gpio3 2 GPIO_ACTIVE_HIGH>;
>> +		enable-active-high;
>> +		regulator-always-on;
>>  	};
>>  
>>  	reg_vdd_5v: regulator-5v {
>> @@ -78,6 +80,7 @@ reg_vdd_5v: regulator-5v {
>>  		regulator-name = "vdd-5v";
>>  		regulator-min-microvolt = <5000000>;
>>  		regulator-max-microvolt = <5000000>;
>> +		regulator-always-on;
> 
> You do not have any on/off control over the regulator.  So how does this
> always-on property make any difference?

Right, this doesn't make a difference and is definitely not a fix, I
will drop it. Anyway, this regulator is just there for completeness of
the hardware description.

> 
>>  	};
>>  };
>>  
>> -- 
>> 2.33.0
>>