linux-kernel - Re: [PATCH v3 5/5] tty: serial: samsung: Fix console registration from module

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Date:   Mon, 13 Dec 2021 12:39:24 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Sam Protsenko <semen.protsenko@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jaewon Kim <jaewon02.kim@...sung.com>,
        Chanho Park <chanho61.park@...sung.com>,
        David Virag <virag.david003@...il.com>,
        Youngmin Nam <youngmin.nam@...sung.com>,
        devicetree@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v3 5/5] tty: serial: samsung: Fix console registration
 from module

On 04/12/2021 20:57, Sam Protsenko wrote:
> On modern Exynos SoCs (like Exynos850) the UART can be implemented as a
> part of USI IP-core. In such case, USI driver is used to initialize USI
> registers, and it also calls of_platform_populate() to instantiate all
> sub-nodes (e.g. serial node) of USI node. When serial driver is
> built-in, but USI driver is a module, and CONFIG_SERIAL_SAMSUNG_CONSOLE
> is enabled, next call chain will happen when loading USI module from
> user space:
> 
>     usi_init
>       v
>     usi_probe
>       v
>     of_platform_populate
>       v
>     s3c24xx_serial_probe
>       v
>     uart_add_one_port
>       v
>     uart_configure_port
>       v
>     register_console
>       v
>     try_enable_new_console
>       v
>     s3c24xx_serial_console_setup
> 
> But because the serial driver is built-in, and
> s3c24xx_serial_console_setup() is marked with __init keyword, that
> symbol will discarded and long gone by that time already, causing failed
> paging request.
> 
> That happens during the next config combination:
> 
>     EXYNOS_USI=m
>     SERIAL_SAMSUNG=y
>     SERIAL_SAMSUNG_CONSOLE=y
> 
> That config should be completely possible, so rather than limiting
> SERIAL_SAMSUNG choice to "m" only when USI=m, remove __init keyword for
> all affected functions.
> 
> Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
> ---
> Changes in v3:
>   - (none)
> 
> Changes in v2:
>   - This patch is added in v2
> 
>  drivers/tty/serial/samsung_tty.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>


Best regards,
Krzysztof