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From:   Maxime Jourdan <maxi.jourdan@wanadoo.fr>
Date:   Fri, 10 Aug 2018 08:42:58 +0200
Message-ID: <CAHStOZ5RrB_=vhHwN22ajcbmWW_F04RdJTiE1ZLSDqhvwT5Zkg@mail.gmail.com>
Subject: Re: [PATCH v2 3/4] ARM64: dts: meson-gx: add dmcbus and canvas nodes.
To:     Neil Armstrong <narmstrong@baylibre.com>
Cc:     Jerome Brunet <jbrunet@baylibre.com>,
        Maxime Jourdan <maxi.jourdan@wanadoo.fr>,
        Kevin Hilman <khilman@baylibre.com>,
        linux-amlogic <linux-amlogic@lists.infradead.org>,
        linux-arm-kernel@lists.infradead.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        devicetree@vger.kernel.org
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2018-08-09 9:53 GMT+02:00 Neil Armstrong <narmstrong@baylibre.com>:
> On 08/08/2018 10:41, Jerome Brunet wrote:
>> On Wed, 2018-08-08 at 00:00 +0200, Maxime Jourdan wrote:
>>> Wrap the canvas node in a syscon node.
>>>
>>> Signed-off-by: Maxime Jourdan <maxi.jourdan@wanadoo.fr>
>>> ---
>>>  arch/arm64/boot/dts/amlogic/meson-gx.dtsi | 17 +++++++++++++++++
>>>  1 file changed, 17 insertions(+)
>>>
>>> diff --git a/arch/arm64/boot/dts/amlogic/meson-gx.dtsi b/arch/arm64/boot/dts/amlogic/meson-gx.dtsi
>>> index b8dc4dbb391b..c98198662ae2 100644
>>> --- a/arch/arm64/boot/dts/amlogic/meson-gx.dtsi
>>> +++ b/arch/arm64/boot/dts/amlogic/meson-gx.dtsi
>>> @@ -423,6 +423,23 @@
>>>                      };
>>>              };
>>>
>>> +            dmcbus: bus@c8838000 {
>>> +                    compatible = "simple-bus";
>>> +                    reg = <0x0 0xc8838000 0x0 0x1000>;
>>> +                    #address-cells = <2>;
>>> +                    #size-cells = <2>;
>>> +                    ranges = <0x0 0x0 0x0 0xc8838000 0x0 0x1000>;
>>> +
>>> +                    sysctrl_DMC: system-controller@0 {
>>> +                            compatible = "amlogic,gx-dmc-sysctrl", "syscon", "simple-mfd";
>>> +                            reg = <0x0 0x0 0x0 0x1000>;
>>> +
>>> +                            canvas: canvas-provider@0 {
>>> +                                    compatible = "amlogic,canvas";
>>
>> If there is only one canvas provider under "sysctrl_DMC" and it has no reg
>> property , you should not put a unit-address (@0) here. (same for the
>> documentation patch)
>>
>> You may have seen unit-address without a reg property used elsewhere (ASoC
>> simple-card, my recent axg-sound-card), when there is multiple node with the
>> same node-name (ex: dai-link).

Ack.

>> As Martin pointed out, the DT spec says we should not use unit-address unless
>> there is a reg property. We did not get Rob's view on this and we might have to
>> update this later on. In your case, unless I missed something, you should
>> definitely not have it
>>
>> nitpick regarding the node-name (canvas-provider). If appropriate, we should try
>> to stick to one of the generic names proposed in the spec. I wonder if the
>> canvas provider could be viewed as a "memory" or "memory-controller"
>
> It's not really a memory or memory-controller, it's a Lookup Table on top of the memory controller,
> nothing really matches here...

Thanks for the comments. It will be "video-lut" as suggested.

>>
>> So, what about this ? Just a proposition, feel free to comment ;)
>>
>>       sysctrl_DMC: system-controller@0 {                                                      compatib
>> le = "amlogic,gx-dmc-sysctrl", "syscon", "simple-mfd";>               reg =
>> <0x0 0x0 0x0 0x1000>;
>>
>>               canvas: memory-controller {
>>                       compatible = "amlogic,canvas";
>>               }
>>
>> [...]
>>
>>
>>> +                            };
>>> +                    };
>>> +            };
>>> +
>>>              hiubus: bus@c883c000 {
>>>                      compatible = "simple-bus";
>>>                      reg = <0x0 0xc883c000 0x0 0x2000>;
>>
>>
>