Message-ID: <fbadbd75-ac68-fa06-9303-76892567d179@canonical.com>
Date:   Mon, 13 Dec 2021 12:39:24 +0100
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Subject: Re: [PATCH v3 5/5] tty: serial: samsung: Fix console registration
 from module
Content-Language: en-US
To:     Sam Protsenko <semen.protsenko@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Jaewon Kim <jaewon02.kim@samsung.com>,
        Chanho Park <chanho61.park@samsung.com>,
        David Virag <virag.david003@gmail.com>,
        Youngmin Nam <youngmin.nam@samsung.com>,
        devicetree@vger.kernel.org, linux-serial@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-samsung-soc@vger.kernel.org
References: <20211204195757.8600-1-semen.protsenko@linaro.org>
 <20211204195757.8600-6-semen.protsenko@linaro.org>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
In-Reply-To: <20211204195757.8600-6-semen.protsenko@linaro.org>
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Precedence: bulk

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@linaro.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@canonical.com>


Best regards,
Krzysztof