linux-kernel - Re: [PATCH v2] Revert "tty: serial: meson: Add a earlycon for the T7 SoC"

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Message-ID: <09735262-1bc0-40cf-b139-22cccf70bcab@linux.com>
Date:   Sun, 27 Aug 2023 11:04:36 +0100
From:   Lucas Tanure <tanure@...ux.com>
To:     Neil Armstrong <neil.armstrong@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Kevin Hilman <khilman@...libre.com>
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH v2] Revert "tty: serial: meson: Add a earlycon for the T7
 SoC"

On 27-08-2023 10:48, Neil Armstrong wrote:
> Hi Lucas,
> 
> Le 27/08/2023 à 10:29, Lucas Tanure a écrit :
>> This reverts commit 6a4197f9763325043abf7690a21124a9facbf52e.
>> New SoC will use ttyS0 instead of ttyAML, so T7 SoC doesn't need a 
>> OF_EARLYCON_DECLARE.
>>
>> Signed-off-by: Lucas Tanure <tanure@...ux.com>
>> ---
>> Since V1:
>> - add Signed-off-by:
>>
>>   drivers/tty/serial/meson_uart.c | 2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/drivers/tty/serial/meson_uart.c 
>> b/drivers/tty/serial/meson_uart.c
>> index c4f61d82fb727..790d910dafa5d 100644
>> --- a/drivers/tty/serial/meson_uart.c
>> +++ b/drivers/tty/serial/meson_uart.c
>> @@ -648,8 +648,6 @@ meson_serial_early_console_setup(struct 
>> earlycon_device *device, const char *opt
>>   OF_EARLYCON_DECLARE(meson, "amlogic,meson-ao-uart",
>>               meson_serial_early_console_setup);
>> -OF_EARLYCON_DECLARE(meson, "amlogic,t7-uart",
>> -            meson_serial_early_console_setup);
>>   #define MESON_SERIAL_CONSOLE_PTR(_devname) 
>> (&meson_serial_console_##_devname)
>>   #else
> 
> How do you use earlycon with this removed ?
> 
> Neil
This is my kernel cmdline:
console=ttyS0,921600 no_console_suspend earlycon=ttyS0,0xfe078000

And I can see my log:
boot 64bit kernel
[    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd092]
[    0.000000] Linux version 6.5.0-rc7-next-20230825+ (tanureal@...en) 
(aarch64-none-linux-gnu-gcc (GNU Toolchain for the A-profile 
Architecture 10.3-2021.07 (arm-10.29)) 10.3.1 20210621, GNU ld (GNU 
Toolchain fo3
[    0.000000] KASLR disabled due to lack of seed
[    0.000000] Machine model: Khadas vim4
[    0.000000] OF: reserved mem: 0x0000000005000000..0x00000000052fffff 
(3072 KiB) nomap non-reusable secmon@...0000
[    0.000000] OF: reserved mem: 0x0000000005300000..0x00000000072fffff 
(32768 KiB) nomap non-reusable secmon@...0000
...
[    0.079368] io scheduler mq-deadline registered
[    0.079374] io scheduler kyber registered
[    0.079549] io scheduler bfq registered
[    0.083373] fe078000.serial: ttyS0 at MMIO 0xfe078000 (irq = 14, 
base_baud = 1500000) is a meson_uart
[    0.083403] printk: console [ttyS0] enabled

As the log is OK, and T7 for now is binding against S4 code we should 
drop this patch and add a S4 one if needed.

But just having this log is not enough for testing earlycon?
I am assuming that by just having the log since 0.0000 is a good sign 
that earlycon is working.
Could you give further guidance?

Lucas Tanure