linux-kernel - Re: [PATCH v12 1/1] serial: core: Start managing serial controllers to enable runtime PM

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Date:   Thu, 1 Jun 2023 16:16:16 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Dhruva Gole <d-gole@...com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        John Ogness <john.ogness@...utronix.de>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-omap@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH v12 1/1] serial: core: Start managing serial controllers
 to enable runtime PM

On 01.06.2023 15:20, Tony Lindgren wrote:
> * Tony Lindgren <tony@...mide.com> [230601 11:12]:
>> * Marek Szyprowski <m.szyprowski@...sung.com> [230601 11:00]:
>>> This patch landed in today's linux next-20230601 as commit 84a9582fd203
>>> ("serial: core: Start managing serial controllers to enable runtime
>>> PM"). Unfortunately it breaks booting some of my test boards. This can
>>> be easily reproduced with QEMU and ARM64 virt machine. The last message
>>> I see in the log is:
>>>
>>> [    3.084743] Run /sbin/init as init process
>> OK thanks for the report. I wonder if this issue is specific to ttyAM
>> serial port devices somehow?
> Looks like the problem happens with serial port drivers that use
> arch_initcall():
>
> $ git grep arch_initcall drivers/tty/serial/
> drivers/tty/serial/amba-pl011.c:arch_initcall(pl011_init);
> drivers/tty/serial/mps2-uart.c:arch_initcall(mps2_uart_init);
> drivers/tty/serial/mvebu-uart.c:arch_initcall(mvebu_uart_init);
> drivers/tty/serial/pic32_uart.c:arch_initcall(pic32_uart_init);
> drivers/tty/serial/serial_base_bus.c:arch_initcall(serial_base_init);
> drivers/tty/serial/xilinx_uartps.c:arch_initcall(cdns_uart_init);
>
> We have serial_base_bus use module_init() so the serial core controller
> and port device associated with the physical serial port are not probed.
>
> The patch below should fix the problem you're seeing, care to test and
> if it works I'll post a proper fix?

Right, this fixes my issue. Feel free to add:

Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>

Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>


> Note that if we ever have cases where uart_add_one_port() gets called
> even earlier, we should just call serial_base_init() directly when
> adding the first port.
>
> Regards,
>
> Tony
>
> 8< ------------------
> diff --git a/drivers/tty/serial/serial_base_bus.c b/drivers/tty/serial/serial_base_bus.c
> --- a/drivers/tty/serial/serial_base_bus.c
> +++ b/drivers/tty/serial/serial_base_bus.c
> @@ -186,7 +186,7 @@ static int serial_base_init(void)
>   
>   	return ret;
>   }
> -module_init(serial_base_init);
> +arch_initcall(serial_base_init);
>   
>   static void serial_base_exit(void)
>   {

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland