linux-kernel - Re: [PATCH v2 1/3] dt-bindings: phy: jh7110-usb-phy: Add sys-syscon property

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Message-ID: <20240903-gating-shamrock-c0d4415d1eb3@squawk>
Date: Tue, 3 Sep 2024 10:42:30 +0100
From: Conor Dooley <conor@...nel.org>
To: Minda Chen <minda.chen@...rfivetech.com>
Cc: Conor Dooley <conor.dooley@...rochip.com>,
	Jan Kiszka <jan.kiszka@...mens.com>, Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	"linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: phy: jh7110-usb-phy: Add sys-syscon
 property

On Mon, Sep 02, 2024 at 09:19:29AM +0000, Minda Chen wrote:
> 
> 
> > 
> > On Thu, Aug 15, 2024 at 10:33:55AM +0000, Minda Chen wrote:
> > >
> > >
> > > >
> > > > On Tue, Aug 13, 2024 at 07:31:50AM +0200, Jan Kiszka wrote:
> > > > > On 12.08.24 17:55, Conor Dooley wrote:
> > > > > > On Mon, Aug 12, 2024 at 04:15:51PM +0200, Jan Kiszka wrote:
> > > > > >> From: Jan Kiszka <jan.kiszka@...mens.com>
> > > > > >>
> > > > > >> Analogously to the PCI PHY, access to sys_syscon is needed to
> > > > > >> connect the USB PHY to its controller.
> > > > > >>
> > > > > >> Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
> > > > > >> Reviewed-by: Rob Herring (Arm) <robh@...nel.org>
> > > > > >> ---
> > > > > >> CC: Rob Herring <robh@...nel.org>
> > > > > >> CC: Krzysztof Kozlowski <krzk+dt@...nel.org>
> > > > > >> CC: Conor Dooley <conor+dt@...nel.org>
> > > > > >> ---
> > > > > >>  .../bindings/phy/starfive,jh7110-usb-phy.yaml         | 11
> > > > +++++++++++
> > > > > >>  1 file changed, 11 insertions(+)
> > > > > >>
> > > > > >> diff --git
> > > > > >> a/Documentation/devicetree/bindings/phy/starfive,jh7110-usb-phy
> > > > > >> .yam
> > > > > >> l
> > > > > >> b/Documentation/devicetree/bindings/phy/starfive,jh7110-usb-phy
> > > > > >> .yam l index 269e9f9f12b6..eaf0050c6f17 100644
> > > > > >> ---
> > > > > >> a/Documentation/devicetree/bindings/phy/starfive,jh7110-usb-phy
> > > > > >> .yam
> > > > > >> l
> > > > > >> +++ b/Documentation/devicetree/bindings/phy/starfive,jh7110-usb
> > > > > >> +++ -phy
> > > > > >> +++ .yaml
> > > > > >> @@ -19,6 +19,16 @@ properties:
> > > > > >>    "#phy-cells":
> > > > > >>      const: 0
> > > > > >>
> > > > > >> +  starfive,sys-syscon:
> > > > > >> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > > > > >> +    items:
> > > > > >> +      - items:
> > > > > >> +          - description: phandle to System Register Controller
> > > > sys_syscon node.
> > > > > >> +          - description: PHY connect offset of
> > > > SYS_SYSCONSAIF__SYSCFG register for USB PHY.
> > > > > >
> > > > > > Why is having a new property for this required? The devicetree
> > > > > > only has a single usb phy, so isn't it sufficient to look up the
> > > > > > syscon by compatible, rather than via phandle + offset?
> > > > > >
> > > > >
> > > > > I didn't design this, I just copied it from
> > > > > starfive,jh7110-pcie-phy.yaml. As that already exists, I'm neither
> > > > > sure we want to change that anymore nor deviate in the pattern here.
> > > >
> > > > To be honest, I think some of the other users of phandle + offset on
> > > > this soc were just copy-pasted without thinking about whether or not they
> > were required too.
> > > > This one seems like it should just be a lookup by compatible in the
> > > > driver instead of by phandle. As a bonus, it will work with existing
> > > > devicetrees - whereas your current implementation will fail to probe
> > > > on systems that have the old devicetree, a regression for systems
> > > > running with that devicetree and downstream firmware.
> > > >
> > > > Cheers,
> > > > Conor.
> > > >
> > > Hi Conor
> > > I know you would like to put the offset value to the code, Just set syscon in dts.
> > > Just like pcie-starfive.c. right?
> > 
> > No, not quite. That still uses a phandle lookup, I was talking about using
> > syscon_regmap_lookup_by_compatible().
> 
> Okay. Using syscon_regmap_lookup_by_compatible() can just modify the driver code only.
> But syscon_regmap_lookup_by_compatible() is not exist in uboot now. If I want to enable
> CONFIG_OF_UPSTREAM in uboot. I have to add this function in u-boot...

You can use
	node = ofnode_by_compatible(ofnode_null(), "foo");
	*regmap = syscon_node_to_regmap(node);
in U-Boot.


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