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Date:   Thu, 14 Apr 2022 14:17:04 +0200
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Subject: Re: [PATCH V2 3/3] serial: stm32: add earlycon support
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To:     Geert Uytterhoeven <geert@linux-m68k.org>
CC:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Jiri Slaby <jirislaby@kernel.org>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Erwan Le Ray <erwan.leray@foss.st.com>,
        "open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>
References: <20220408122636.505737-1-valentin.caron@foss.st.com>
 <20220408122636.505737-4-valentin.caron@foss.st.com>
 <CAMuHMdWD8fxeqPUaT_CwnYdq02aaTsnQM_G-YyOGWooS5epCeQ@mail.gmail.com>
From:   Valentin CARON <valentin.caron@foss.st.com>
In-Reply-To: <CAMuHMdWD8fxeqPUaT_CwnYdq02aaTsnQM_G-YyOGWooS5epCeQ@mail.gmail.com>
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On 4/11/22 16:59, Geert Uytterhoeven wrote:
> Hi Valentin,
>
> On Fri, Apr 8, 2022 at 3:14 PM Valentin Caron
> <valentin.caron@foss.st.com> wrote:
>> Add early console support in stm32 uart driver.
>>
>> Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>
>> Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
> Thanks for your patch!
>
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -1264,6 +1264,12 @@
>>                          address must be provided, and the serial port must
>>                          already be setup and configured.
>>
>> +               stm32,<addr>
>> +                       Use early console provided by ST Microelectronics
>> +                       serial driver for STM32 SoCs. A valid base address
>> +                       must be provided, and the serial port must already
>> +                       be setup and configured.
> Why do you need this parameter?
>
> Given this driver uses DT, can't it figure out the serial port address
> from chosen/stdout-path?
>
> +OF_EARLYCON_DECLARE(stm32, "st,stm32h7-uart", early_stm32_h7_serial_setup);
> +OF_EARLYCON_DECLARE(stm32, "st,stm32f7-uart", early_stm32_f7_serial_setup);
> +OF_EARLYCON_DECLARE(stm32, "st,stm32-uart", early_stm32_f4_serial_setup);
>
> Gr{oetje,eeting}s,
>
>                          Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                  -- Linus Torvalds

Hi Geert,

I took the example of other serial drivers.
Both methods work (with earlycon/stdout-path and with 
earlycon=stm32,0xXXXXXXX)
but your right, the second will probably never used on this driver.

Should I remove it ?

Thanks,
Valentin