linux-kernel - Re: [PATCH v3 4/8] phy: rockchip-usb: add compatible values for rk3066a and rk3188

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Date:	Sun, 22 Nov 2015 20:49:21 +0100
From:	Heiko Stuebner <heiko@...ech.de>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Kishon Vijay Abraham I <kishon@...com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Romain Perier <romain.perier@...il.com>,
	Arnd Bergmann <arnd@...db.de>, Lin Huang <hl@...k-chips.com>
Subject: Re: [PATCH v3 4/8] phy: rockchip-usb: add compatible values for rk3066a and rk3188

Am Donnerstag, 19. November 2015, 16:32:23 schrieb Doug Anderson:
> Heiko,
> 
> On Thu, Nov 19, 2015 at 1:22 PM, Heiko Stuebner <heiko@...ech.de> wrote:
> > We need custom handling for these two socs in the driver shortly,
> > so add the necessary compatible values to binding and driver.
> >
> > Signed-off-by: Heiko Stuebner <heiko@...ech.de>
> > ---
> >  Documentation/devicetree/bindings/phy/rockchip-usb-phy.txt | 5 ++++-
> >  drivers/phy/phy-rockchip-usb.c                             | 2 ++
> >  2 files changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/devicetree/bindings/phy/rockchip-usb-phy.txt 
b/Documentation/devicetree/bindings/phy/rockchip-usb-phy.txt
> > index 826454a..9b37242 100644
> > --- a/Documentation/devicetree/bindings/phy/rockchip-usb-phy.txt
> > +++ b/Documentation/devicetree/bindings/phy/rockchip-usb-phy.txt
> > @@ -1,7 +1,10 @@
> >  ROCKCHIP USB2 PHY
> >
> >  Required properties:
> > - - compatible: rockchip,rk3288-usb-phy
> > + - compatible: matching the soc type, one of
> > +     "rockchip,rk3066a-usb-phy"
> > +     "rockchip,rk3188-usb-phy"
> > +     "rockchip,rk3288-usb-phy"
> 
> I can never quite keep it straight how this is supposed to work, but
> since previously only "rockchip,rk3288-usb-phy" was supported and now
> we have these new compatible strings, I would have expected the new
> strings to specify the old ones as fallback.  That would mean your
> choices would be:
> 
> - "rockchip,rk3288-usb-phy" - A real rk3288
> - "rockchip,rk3188-usb-phy", "rockchip,rk3288-usb-phy" - A rk3188 with
> fallback to 3288 driver.
> - "rockchip,rk3066a-usb-phy", "rockchip,rk3288-usb-phy" - A rk3066a
> with fallback to 3288 driver.

How this is supposed to be done also is sometimes confusing for me :-)

But I don't think that specifying the "fallbacks" is part of the binding at 
all, when the binding really is done in a soc-specific way.  For example 
following the suggestion of the dt-maintainers at the time we're specifying 
the uarts as

	compatible = "rockchip,rk3288-uart", "snps,dw-apb-uart"

as a measure to use a more-special driver if there is ever the need for it. 
But here the "snps,dw-apb-uart" actually is a superset (a more generic 
implementation), while in the usb-uart-case


> That means that if you land the dts changes without the driver changes
> that things still work OK.

We already have the alternative for the usb-phys in the devicetree, but I 
still don't think that this alternative is part of the binding itself :-)


Heiko
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