linux-kernel - Re: [PATCH V2 1/2] dt-bindings: bcm-ns-usb2-phy: rework binding to use CRU syscon

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Date:   Tue, 15 Jan 2019 14:53:00 -0600
From:   Rob Herring <robh@...nel.org>
To:     Rafał Miłecki <zajec5@...il.com>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, Hauke Mehrtens <hauke@...ke-m.de>,
        bcm-kernel-feedback-list@...adcom.com,
        Rafał Miłecki <rafal@...ecki.pl>
Subject: Re: [PATCH V2 1/2] dt-bindings: bcm-ns-usb2-phy: rework binding to
 use CRU syscon

On Tue, Jan 08, 2019 at 01:39:06PM +0100, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@...ecki.pl>
> 
> USB 2.0 PHY is a hardware block that happens to use two registers from
> the CRU block to setup a single PLL. It's not part of the CRU or DMU
> and so its binding shouldn't cover the whole DMU.
> 
> The correct way of handling this is to reference CRU block node using a
> syscon. Document that & deprecate the old way.
> 
> Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
> ---
> V2: use syscon@ in example (thanks Ray)
> ---
>  .../devicetree/bindings/phy/bcm-ns-usb2-phy.txt    | 27 ++++++++++++++++++----
>  1 file changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/phy/bcm-ns-usb2-phy.txt b/Documentation/devicetree/bindings/phy/bcm-ns-usb2-phy.txt
> index a7aee9ea8926..2cafee6b4a8b 100644
> --- a/Documentation/devicetree/bindings/phy/bcm-ns-usb2-phy.txt
> +++ b/Documentation/devicetree/bindings/phy/bcm-ns-usb2-phy.txt
> @@ -2,19 +2,38 @@ Driver for Broadcom Northstar USB 2.0 PHY
>  
>  Required properties:
>  - compatible: brcm,ns-usb2-phy
> -- reg: iomem address range of DMU (Device Management Unit)
> -- reg-names: "dmu", the only needed & supported reg right now
> +- syscon-cru: phandle to the CRU (Central Resource Unit) syscon
>  - clocks: USB PHY reference clock
>  - clock-names: "phy-ref-clk", the only needed & supported clock right now
>  
> +Deprecated:
> +
> +PHY block should not claim the whole DMU so such a binding has been deprecated.
> +It only requires to access few CRU (a DMU subblock) registers and that should be
> +handled with a syscon since CRU is a MFD (Multi-Function Device).
> +
> +- reg: iomem address range of DMU (Device Management Unit)
> +- reg-names: "dmu", the only needed & supported reg right now
> +
>  To initialize USB 2.0 PHY driver needs to setup PLL correctly. To do this it
>  requires passing phandle to the USB PHY reference clock.
>  
>  Example:
> +	dmu@...0c000 {
> +		compatible = "simple-bus";

DMU sounds like some sort of block, not just a bus.

> +		ranges = <0 0x1800c000 0x1000>;
> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +
> +		cru: syscon@100 {
> +			compatible = "syscon", "simple-mfd";

Those 2 compatibles alone are not valid. And 'simple-mfd' implies child 
nodes.

Without any knowledge of what else is in the DMU, I can't give any 
advice as to what this should look like instead.

> +			reg = <0x100 0x1a4>;
> +		};
> +	};
> +
>  	usb2-phy {
>  		compatible = "brcm,ns-usb2-phy";
> -		reg = <0x1800c000 0x1000>;
> -		reg-names = "dmu";
> +		syscon-cru = <&cru>;

No need for this. Make it a child of cru node.

There's not a contiguous range of phy registers? If there are, keep 
'reg' even if Linux doesn't (currently) use it.

>  		#phy-cells = <0>;
>  		clocks = <&genpll BCM_NSP_GENPLL_USB_PHY_REF_CLK>;
>  		clock-names = "phy-ref-clk";
> -- 
> 2.13.7
>