[PATCH 1/2] drm/panel: Augment the TPO TPG110 bindings

[Andrzej Hajda]

On 01.07.2018 21:01, Linus Walleij wrote:
> On Wed, Jun 27, 2018 at 7:21 PM Rob Herring <robh at kernel.org> wrote:
>> On Thu, Jun 21, 2018 at 08:49:41PM +0200, Linus Walleij wrote:
>>> +This panel driver can driver a variety of panels. It requires
>> s/can driver/can drive/
>>
>> Though what a driver supports is irrelevant to the binding...
> It it not a software driver the text is referring to. It is a
> electrical interface to a panel. Like how a TTL circuit connected
> to a LED is referred to as a "LED driver", it's simply what the
> industry calls these things.
>
> So there are two things: the panel driver and the panel, the
> same panel driver is used with several panels. What the
> electronics engineer will do is put a panel driver like this
> into his design and then connect some panel s/he finds
> in the right quantity in the streets of Shenzhen.
>
>> If you remove timings, how does it drive a variety of panels? Just by
>> compatible?
> Yes.
>
> Like we did for
> Documentation/devicetree/bindings/display/panel/ilitek,ili9322.txt
> which is similar to this.
>
> In fact I think many panel drivers are just sloppily slipping in
> under the radar as "panels" in our bindings.
>
>> That would mean "tpo,tpg110" alone is not valid nor useful
>> as a fallback.
> Actually it is. The hardware is wired up to the desired
> resolution with hardware straps, which appear in
> the registers the (software) driver can read out so
> this is ideally self-describing hardware.
>
> But for the event that something needs tweaking in the
> future, like we overspecify say SoCs, I include the
> exact system on which it is deployd as a separate
> compatible string.
>
>>> +a few GPIO lines for control of its reset line and custom serial
>>> +protocol.
>>>
>>>  Required properties:
>>> -- compatible : "tpo,tpg110"
>>> +- compatible : one of:
>>> +  "ste,nomadik-nhk15-display", "tpo,tpg110"
>>> +  "tpo,tpg110"
>>>  - grestb-gpios : panel reset GPIO
>>>  - scen-gpios : serial control enable GPIO
>>>  - scl-gpios : serial control clock line GPIO
>>>  - sda-gpios : serial control data line GPIO
>> I2C? That should be done differently...
> It is not I2C, the lines are just named confusingly
> similar. None of the I2C (-like) protocols apply.
> I was similarly confused when I first implemented it.
>
> (Maybe I should add a comment to explain this.)

I have grepped Internet, out of curiosity, and it seems it is so-called
3-wire spi [1].

[1]:
http://aitendo3.sakura.ne.jp/aitendo_data/product_img/lcd/tft/T43P00/TPG110%20Customer%20Spec_0.6.pdf


Regards
Andrzej

>
> Yours,
> Linus Walleij
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