linux-kernel - Re: [RFC PATCH 02/11] dt-bindings: phy: add cpsw port interface mode selection phy bindings

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Date:   Tue, 9 Oct 2018 15:07:30 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Sekhar Nori <nsekhar@...com>, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [RFC PATCH 02/11] dt-bindings: phy: add cpsw port interface mode
 selection phy bindings

* Grygorii Strashko <grygorii.strashko@...com> [181009 22:04]:
> 
> 
> On 10/09/2018 03:30 PM, Tony Lindgren wrote:
> > * Grygorii Strashko <grygorii.strashko@...com> [181009 20:10]:
> >>
> >>
> >> On 10/09/2018 09:40 AM, Tony Lindgren wrote:
> >>> * Grygorii Strashko <grygorii.strashko@...com> [181008 23:54]:
> >>>> +Examples:
> >>>> +	phy_gmii_sel: phy-gmii-sel {
> >>>> +		compatible = "ti,am3352-phy-gmii-sel";
> >>>> +		syscon-scm = <&scm_conf>;
> >>>> +		#phy-cells = <2>;
> >>>> +	};
> >>>
> >>> Now that this driver can live in it's proper place in the
> >>
> >> right
> >>
> >>> dts, you may want to consider just using standard reg
> >>> property for it instead of the syscon-scm. And also get
> >>> rid of the syscon reads and writes.
> >>
> >> Could you help clarify how to get syscon in this case?
> >> syscon_node_to_regmap(dev->parent->of_node)?
> > 
> > Hmm I don't think you need syscon at all now. You can just
> > ioremap the register(s) and use readl/writel and that's it.
> > Or use regmap without syscon if you prefer that.
> 
> It will overlap with already remapped SCM syscon and i'd like to avoid this.
> + it seems common practice to use syscon for devices/drivers which are
> child to SCM node - makes overall system more consistent.

Well it was just set up with syscon in deperation earlier with
drivers just blindly mapping registers outside of their
range..

> > The ioremap in this case should be hitting cached ranges
> > anyways, so no extra overhead there.
> > 
> >> Also, there are could be more then one gmii_sel registers in SCM in the future,
> >> so I hidden offsets in of_match data.
> >> As result, "reg" not needed at all now.
> > 
> > But then you have to patch driver for various SoCs
> > instead of just configuring the standard reg property
> > in the dts file :)
> 
> Problem is that they are not guarantee to be standard between SoC's families 
> (number of regs and fields placement), as result it might require to change
> driver any way for various SoCs to handle properly new fields placement.
> 
> I prefer to fix driver then fight with DT ;) as it's static for SoC family
> and need to be changed only once when new SoC family introduced.

Fine with me, that can be changed later too no problem.

Regards,

Tony