linux-kernel - Re: [RFC PATCH] ARM: dts: imx6qdl: specify vcc-supply for NOP USB PHYs

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Message-ID: <20210119085700.GB4356@dragon>
Date:   Tue, 19 Jan 2021 16:57:02 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] ARM: dts: imx6qdl: specify vcc-supply for NOP USB
 PHYs

On Fri, Nov 13, 2020 at 04:28:55PM +0100, Ahmad Fatoum wrote:
> The SoC dtsi lists a NOP USB PHY for each of the two HSIC-only USB
> controllers. Their device tree node doesn't indicate a vcc-supply
> resulting in:
> 
>   usb_phy_generic usbphynop1: supply vcc not found, using dummy regulator
>   usb_phy_generic usbphynop2: supply vcc not found, using dummy regulator

So the patch is all for removing this kernel message, with introducing
the following potential breakage?

Shawn

> 
> warnings on boot up. The USB IP vcc-supply - separate from the vusb - is
> hardwired to LDO_2P5[1], which we already have a device tree node for.
> Reference it for the dummy "phy" as well.
> 
> This will lead to breakage (probe deferment) for kernels that:
>   - Use a HSIC USB controller
>   - Use this new device tree
>   - but have CONFIG_REGULATOR_ANATOP disabled
> 
> Because while the regulator is always-on, it can't be resolved when
> there is no driver for it.
> 
> As there are
> 
>   - no affected upstream device trees
>   - existing device trees are unaffected without recompilation
>   - disabling CONFIG_REGULATOR_ANATOP is explicitly a non-recommended
>     configuration per symbol help text
> 
> this potential breakage is deemed acceptable.
> 
> [1]: i.MX 6Dual/6Quad Reference Manual, Rev. C,
>      Figure 53-1. Power System Overview
> 
> Cc: Frieder Schrempf <frieder.schrempf@...tron.de>
> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
> ---
>  arch/arm/boot/dts/imx6qdl.dtsi | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/imx6qdl.dtsi b/arch/arm/boot/dts/imx6qdl.dtsi
> index 43edbf1156c7..22e4c142de13 100644
> --- a/arch/arm/boot/dts/imx6qdl.dtsi
> +++ b/arch/arm/boot/dts/imx6qdl.dtsi
> @@ -131,11 +131,13 @@ pmu: pmu {
>  
>  	usbphynop1: usbphynop1 {
>  		compatible = "usb-nop-xceiv";
> +		vcc-supply = <&reg_vdd2p5>;
>  		#phy-cells = <0>;
>  	};
>  
>  	usbphynop2: usbphynop2 {
>  		compatible = "usb-nop-xceiv";
> +		vcc-supply = <&reg_vdd2p5>;
>  		#phy-cells = <0>;
>  	};
>  
> -- 
> 2.28.0
>