linux-kernel - Re: [linux-sunxi] [PATCH v2 5/7] arm64: allwinner: a64: add necessary device tree nodes for DE2 CCU

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Date:   Sun, 24 Jun 2018 00:06:27 +1000
From:   Julian Calaby <julian.calaby@...il.com>
To:     Icenowy Zheng <icenowy@...c.io>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>, jagan@...rulasolutions.com,
        jernej.skrabec@...l.net, devicetree <devicetree@...r.kernel.org>,
        "Mailing List, Arm" <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:COMMON CLK FRAMEWORK" <linux-clk@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [linux-sunxi] [PATCH v2 5/7] arm64: allwinner: a64: add necessary
 device tree nodes for DE2 CCU

Hi Icenowy,

On Fri, Jun 22, 2018 at 10:49 PM Icenowy Zheng <icenowy@...c.io> wrote:
>
> As we have all necessary parts to enable the DE2 CCU on the Allwinner
> A64 SoC, add the needed device tree nodes, including the DE2 CCU itself
> and the DE2 bus.
>
> The "mixer0-lcd0" simplefb device node is updated to use the DE2 CCU.
>
> Signed-off-by: Icenowy Zheng <icenowy@...c.io>
> ---
> Changes in v2:
> - Drop SRAM controller device tree node addition (as it's already added
>   as part of syscon change.)
> - Fix the clock reference in LCD SimpleFB.
>
>  arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 30 +++++++++++++++----
>  1 file changed, 24 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> index ff2ddde1e117..318c4ba8ae9f 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> @@ -58,17 +60,12 @@
>                 #size-cells = <1>;
>                 ranges;
>
> -/*
> - * The pipeline mixer0-lcd0 depends on clock CLK_MIXER0 from DE2 CCU.
> - * However there is no support for this clock on A64 yet, so we depend
> - * on the upstream clocks here to keep them (and thus CLK_MIXER0) up.
> - */
>                 simplefb_lcd: framebuffer-lcd {
>                         compatible = "allwinner,simple-framebuffer",
>                                      "simple-framebuffer";
>                         allwinner,pipeline = "mixer0-lcd0";
>                         clocks = <&ccu CLK_TCON0>,
> -                                <&ccu CLK_DE>, <&ccu CLK_BUS_DE>;
> +                                <&display_clocks CLK_MIXER0>;

Doesn't this technically break simplefb if this DT is used with a
Linux that doesn't have the display clock driver?

Do we care about breaking that use-case?

Thanks,

-- 
Julian Calaby

Email: julian.calaby@...il.com
Profile: http://www.google.com/profiles/julian.calaby/