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    SubjectRe: [PATCH 7/7] ARM: dts: sun7i: Add dts file for the A20-linova1-7 HMI
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    Hi Maxime,

    Il 25/04/2018 20:40, Maxime Ripard ha scritto:
    > Hi Giulio,
    >
    > On Tue, Apr 24, 2018 at 08:31:44PM +0200, Giulio Benetti wrote:
    >> LiNova1 is not a board with various headers to connect other peripherals
    >> such display, pcap etc.
    >> It's an HMI that I would consider the same as a Tablet, because it has a
    >> plastic enclosure also.
    >>
    >> So I would like to understand how to manage it in the best way.
    >> Try to consider LiNova1 as a Tablet series, with following list:
    >> LiNova1 4.3" ctp
    >> LiNova1 7" ctp
    >> LiNova1 10.1" ctp
    >> LiNova1 4.3" rtp
    >> LiNova1 7" rtp
    >> LiNova1 10.1" rtp
    >>
    >> Every of those has a slightly different BOM, so they are 6 different
    >> boards with a common base(uP, ram). And same pcb.
    >
    > So the LiNova1 is exactly the same in all these setups, the only
    > difference is that it has a connector that you connect a different
    > display / touchscreen to?
    >
    > If so, that's definitely a case for device tree overlays.

    Yes it is that way. So I proceed with dt overlays.

    >
    >> So I don't know if submit only the common base and provide
    >> separately on our github DT-overlays, or provide as many dts patches
    >> as the HMI number with a base dtsi.
    >
    > That's really up to you, but the overlays will make this much simpler
    > to handle precisely because it will reduce the amount of combinations
    > you have.
    >
    > You can even reduce it in your case to 5 of them, 3 for each panel and
    > 2 for each touchscreen.

    Ah, that's right! Good idea, more "encapsulation".

    >
    >> Basically Micronova provides entire system without the capability to hack
    >> hardware adding shields of various type.
    >>
    >> There are also other 2 LiNova:
    >> LiNova2 and LiNova3
    >
    > Which SoCs are these boards based on?

    A20 on all three. They are slightly between each other.
    Some RS485 more, 1 USB more etc.

    >
    >> So I understand that this could lead to 18 different dts files and 3
    >> dtsi files.
    >
    > Yeah, I'd really like to keep this under control :)

    :)

    >
    >> But with Tablet it should be the same way. For sure people would be
    >> more interested on famous tablets instead of our HMI.
    >>
    >> In the case I need to use dt-overlays, you mean .dto files with
    >> fragments inside loaded by u-boot or runtime, right?
    >
    > You don't have to handcode the fragments anymore with the new syntax,
    > and U-Boot makes it really trivial to use if you use the FIT image
    > format to have multiple overlays bundled in the same image. You can
    > choose to apply them dynamically, for example based on an EEPROM or
    > some other metric to see which combination you have.

    Ah, this is interesting. I'm going to experiment with that.

    >
    >>>>>> +&usb_otg {
    >>>>>> + dr_mode = "otg";
    >>>>>
    >>>>> You're saying that this is a USB-A connector? Then it's not OTG since
    >>>>> it doesn't have an ID pin, this is an host.
    >>>>
    >>>> Right, with a special overlay I will activate Usb Device for RNDIS,
    >>>> so modified as host
    >>>
    >>> That doesn't really make much sense. The USB OTG is wired only using a
    >>> daughter board?
    >>
    >> My fault, I've meant "peripheral" in one case and "host" in another case.
    >> Usually "host".
    >> Are there problem with this?
    >> There is no daughter board.
    >
    > If you have an ID pin and the ability to control VBUS, then you don't
    > need to change the device tree, it's done automatically at runtime by
    > Linux.

    Unfortanetely I don't have ID pin and a common mosfet to control VBUS.
    "peripheral" mode should be used only in debug mode,
    so right dt-overlay can be written to sd-card by ourself or some of our
    customers.

    Thank you very much for all clarifications!

    Giulio.

    >
    > Maxime
    >

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