netdev - Re: [PATCH net-next v2 15/15] arm64: dts: allwinner: a64: add SRAM controller device tree node

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Date:   Wed, 2 May 2018 13:54:37 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Icenowy Zheng <icenowy@...c.io>
Cc:     linux-arm-kernel@...ts.infradead.org, Chen-Yu Tsai <wens@...e.org>,
        Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Corentin Labbe <clabbe.montjoie@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH net-next v2 15/15] arm64: dts: allwinner: a64: add SRAM
 controller device tree node

On Wed, May 02, 2018 at 06:19:51PM +0800, Icenowy Zheng wrote:
> 
> 
> 于 2018年5月2日 GMT+08:00 下午5:53:21, Chen-Yu Tsai <wens@...e.org> 写到:
> >On Wed, May 2, 2018 at 5:51 PM, Maxime Ripard
> ><maxime.ripard@...tlin.com> wrote:
> >> Hi,
> >>
> >> On Wed, May 02, 2018 at 12:12:27AM +0800, Chen-Yu Tsai wrote:
> >>> From: Icenowy Zheng <icenowy@...c.io>
> >>>
> >>> Allwinner A64 has a SRAM controller, and in the device tree
> >currently
> >>> we have a syscon node to enable EMAC driver to access the EMAC clock
> >>> register. As SRAM controller driver can now export regmap for this
> >>> register, replace the syscon node to the SRAM controller device
> >node,
> >>> and let EMAC driver to acquire its EMAC clock regmap.
> >>>
> >>> Signed-off-by: Icenowy Zheng <icenowy@...c.io>
> >>> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
> >>> ---
> >>>  arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 23
> >+++++++++++++++----
> >>>  1 file changed, 19 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> >b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> >>> index 1b2ef28c42bd..1c37659d9d41 100644
> >>> --- a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> >>> +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> >>> @@ -168,10 +168,25 @@
> >>>               #size-cells = <1>;
> >>>               ranges;
> >>>
> >>> -             syscon: syscon@...0000 {
> >>> -                     compatible =
> >"allwinner,sun50i-a64-system-controller",
> >>> -                             "syscon";
> >>> +             sram_controller: sram-controller@...0000 {
> >>> +                     compatible =
> >"allwinner,sun50i-a64-sram-controller";
> >>
> >> I don't think there's anything preventing us from keeping the
> >> -system-controller compatible. It's what was in the DT before, and
> >> it's how it's called in the datasheet.
> >
> >I actually meant to ask you about this. The -system-controller
> >compatible matches the datasheet better. Maybe we should just
> >switch to that one?
> 
> No, if we do the switch the system-controller compatible,
> the device will be probed on the same memory region with
> a syscon on old DTs.

The device hasn't magically changed either. Maybe we just need to add
a check to make sure we don't have the syscon compatible in the SRAM
driver probe so that the double driver issue doesn't happen?

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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