linux-kernel - [PATCH v2 5/5] tty: serial: samsung: Fix console registration from module

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Date:   Tue, 30 Nov 2021 04:27:40 +0200
From:   Sam Protsenko <semen.protsenko@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jiri Slaby <jirislaby@...nel.org>,
        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: [PATCH v2 5/5] tty: serial: samsung: Fix console registration from module

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 v2:
  - This patch is added in v2

 drivers/tty/serial/samsung_tty.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index 61ccb359620a..d002a4e48ed9 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -2500,7 +2500,8 @@ s3c24xx_serial_console_write(struct console *co, const char *s,
 	uart_console_write(cons_uart, s, count, s3c24xx_serial_console_putchar);
 }
 
-static void __init
+/* Shouldn't be __init, as it can be instantiated from other module */
+static void
 s3c24xx_serial_get_options(struct uart_port *port, int *baud,
 			   int *parity, int *bits)
 {
@@ -2563,7 +2564,8 @@ s3c24xx_serial_get_options(struct uart_port *port, int *baud,
 	}
 }
 
-static int __init
+/* Shouldn't be __init, as it can be instantiated from other module */
+static int
 s3c24xx_serial_console_setup(struct console *co, char *options)
 {
 	struct uart_port *port;
-- 
2.30.2