linux-kernel - Re: [PATCH v2 2/2] drm/bridge: anx7688: Add anx7688 bridge driver support

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Message-ID: <5245a8e4-2320-46bd-04fd-f86ce6b17ce7@collabora.com>
Date:   Thu, 5 Mar 2020 16:28:31 +0100
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Vasily Khoruzhick <anarsoul@...il.com>,
        Enric Balletbo Serra <eballetbo@...il.com>
Cc:     Icenowy Zheng <icenowy@...c.io>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        David Airlie <airlied@...ux.ie>, Torsten Duwe <duwe@...e.de>,
        Jonas Karlman <jonas@...boo.se>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Maxime Ripard <maxime@...no.tech>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Collabora Kernel ML <kernel@...labora.com>
Subject: Re: [PATCH v2 2/2] drm/bridge: anx7688: Add anx7688 bridge driver
 support

Hi Vasily,

On 14/2/20 23:22, Vasily Khoruzhick wrote:
> On Fri, Feb 14, 2020 at 2:20 PM Enric Balletbo Serra
> <eballetbo@...il.com> wrote:
>>
>> Hi Vasily,
>>
>> Missatge de Vasily Khoruzhick <anarsoul@...il.com> del dia dv., 14 de
>> febr. 2020 a les 23:17:
>>>
>>> On Fri, Feb 14, 2020 at 1:53 PM Enric Balletbo Serra
>>> <eballetbo@...il.com> wrote:
>>>>
>>>> Hi Vasily,
>>>>
>>>> Missatge de Vasily Khoruzhick <anarsoul@...il.com> del dia dv., 14 de
>>>> febr. 2020 a les 22:36:
>>>>>
>>>>> On Thu, Feb 13, 2020 at 6:54 AM Enric Balletbo i Serra
>>>>> <enric.balletbo@...labora.com> wrote:
>>>>>>
>>>>>> From: Nicolas Boichat <drinkcat@...omium.org>
>>>>>>
>>>>>> ANX7688 is a HDMI to DP converter (as well as USB-C port controller),
>>>>>> that has an internal microcontroller.
>>>>>>
>>>>>> The only reason a Linux kernel driver is necessary is to reject
>>>>>> resolutions that require more bandwidth than what is available on
>>>>>> the DP side. DP bandwidth and lane count are reported by the bridge
>>>>>> via 2 registers on I2C.
>>>>>
>>>>> It is true only for your particular platform where usb-c part is
>>>>> managed by firmware. Pinephone has the same anx7688 but linux will
>>>>> need a driver that manages usb-c in addition to DP.
>>>>>
>>>>> I'd suggest making it MFD driver from the beginning, or at least make
>>>>> proper bindings so we don't have to rework it and introduce binding
>>>>> incompatibilities in future.
>>>>>
>>>>
>>>> Do you have example code on how the ANX7866 is used in pinephone?
>>>> There is a repo somewhere?
>>>
>>> I don't think it's implemented yet. I've CCed Icenowy in case if she
>>> has anything.
>>>
>>
>> It would be good to join the effort. Just because I am curious, there
>> are public schematics for the pinephone that is using that bridge?
> 
> Schematics is available here:
> https://wiki.pine64.org/index.php/PinePhone_v1.1_-_Braveheart#Schematic
> 

Would you mind to check which firmware version is running the anx7688 in
PinePhone, I think should be easy to check with i2c-tools.

Thanks in advance,
 Enric

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