linux-kernel - Re: Support for AMDI0022 UART

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Message-ID: <CAHp75VcLoTsjyQyVAo6cd+HMd+z_irM8ofcenRm0P6CzYGOQNw@mail.gmail.com>
Date:   Sat, 24 Apr 2021 13:25:54 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Maximilian Luz <luzmaximilian@...il.com>
Cc:     "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Wang Hongcheng <annie.wang@....com>, Ken Xue <Ken.Xue@....com>
Subject: Re: Support for AMDI0022 UART

On Fri, Apr 23, 2021 at 10:58 PM Maximilian Luz <luzmaximilian@...il.com> wrote:
>
> Hi all,
>
> I received a report from a Surface Laptop 4 which has a UART that is
> identified as AMDI0022 in ACPI [1] and that does not seem to be
> supported by the kernel yet.
>
>  From what I can tell via ACPI, this is similar to the AMDI0020 [2] UART
> that's already supported by the kernel (well, both are devices with two
> MMIO regions and an interrupt as far as I can tell...). So it's possible
> that all that's needed is adding it to the respective device ID lists
> [3, 4]. Unfortunately, I a) don't have a device to test this myself, b)
> haven't found any more details on that online, and c) don't want to tell
> others to test this without knowing a bit more about that (potentially
> writing random stuff to some unknown MMIO region that I don't know
> anything about doesn't sound as safe to me as I'd like).

To me they look completely the same. Depending on the device which is
connected to the UART, I would suggest just to add an ID and see if it
makes it work.

> Does anyone here have some pointers on what it'd take to support this,
> or any contacts at AMD that could provide more insight?

-- 
With Best Regards,
Andy Shevchenko