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:   Sat, 23 Jun 2018 22:18:21 +0800
From:   Icenowy Zheng <icenowy@...c.io>
To:     julian.calaby@...il.com, Julian Calaby <julian.calaby@...il.com>
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



于 2018年6月23日 GMT+08:00 下午10:06:27, Julian Calaby <julian.calaby@...il.com> 写到:
>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?

1. DT doesn't care forware compatibility.

2. This is a fix for not accurate HW representation. In
fact I have sent the DT with simplefb using DE2 CCU before, but
when they're pending, someone who just wants the simplefb
sent the not temporary version.This must be fixed.

>
>Do we care about breaking that use-case?
>
>Thanks,