Re: [PATCH v1 2/5] tty: serial: meson: redesign the module to platform_driver

neil.armstrong
2023-07-04T14:47:17Z

On 04/07/2023 15:59, Dmitry Rokosov wrote:
> Actually, the meson_uart module is already a platform_driver, but it is
> currently registered manually and the uart core registration is run
> outside the probe() scope, which results in some restrictions. For
> instance, it is not possible to communicate with the OF subsystem
> because it requires an initialized device object.
>
> To address this issue, apply module_platform_driver() instead of direct
> module init/exit routines. Additionally, move uart_register_driver() to
> the driver probe(), and destroy manual console registration because it's
> already run in the uart_register_driver() flow.
>
> Signed-off-by: Dmitry Rokosov <ddrokosov@sberdevices.ru>
> ---
> drivers/tty/serial/meson_uart.c | 46 +++++++--------------------------
> 1 file changed, 10 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
> index 169f028956ae..87c0eb5f2dba 100644
> --- a/drivers/tty/serial/meson_uart.c
> +++ b/drivers/tty/serial/meson_uart.c
> @@ -621,12 +621,6 @@ static struct console meson_serial_console = {
> .data = &meson_uart_driver,
> };
>
> -static int __init meson_serial_console_init(void)
> -{
> - register_console(&meson_serial_console);
> - return 0;
> -}
> -
> static void meson_serial_early_console_write(struct console *co,
> const char *s,
> u_int count)
> @@ -652,9 +646,6 @@ OF_EARLYCON_DECLARE(meson, "amlogic,meson-ao-uart",
>
> #define MESON_SERIAL_CONSOLE (&meson_serial_console)
> #else
> -static int __init meson_serial_console_init(void) {
> - return 0;
> -}
> #define MESON_SERIAL_CONSOLE NULL
> #endif
>
> @@ -738,6 +729,13 @@ static int meson_uart_probe(struct platform_device *pdev)
> if (ret)
> return ret;
>
> + if (!meson_uart_driver.state) {
> + ret = uart_register_driver(&meson_uart_driver);
> + if (ret)
> + return dev_err_probe(&pdev->dev, ret,
> + "failed to register meson-uart driver\n");
> + }

PL010 protects this in a mutex, and I think you should do the same otherwise
if multiple uart probes at the same it will do weird stuff.

> +
> port->iotype = UPIO_MEM;
> port->mapbase = res_mem->start;
> port->mapsize = resource_size(res_mem);
> @@ -776,6 +774,8 @@ static int meson_uart_remove(struct platform_device *pdev)
> uart_remove_one_port(&meson_uart_driver, port);
> meson_ports[pdev->id] = NULL;
>
> + uart_unregister_driver(&meson_uart_driver);
> +

This is dangerous, it will remove the driver even if some uart are still attached to it.

You should probably do like in pl010_remove() and remove only if the last one is removed.

> return 0;
> }
>
> @@ -809,33 +809,7 @@ static struct platform_driver meson_uart_platform_driver = {
> },
> };
>
> -static int __init meson_uart_init(void)
> -{
> - int ret;
> -
> - ret = meson_serial_console_init();
> - if (ret)
> - return ret;
> -
> - ret = uart_register_driver(&meson_uart_driver);
> - if (ret)
> - return ret;
> -
> - ret = platform_driver_register(&meson_uart_platform_driver);
> - if (ret)
> - uart_unregister_driver(&meson_uart_driver);
> -
> - return ret;
> -}
> -
> -static void __exit meson_uart_exit(void)
> -{
> - platform_driver_unregister(&meson_uart_platform_driver);
> - uart_unregister_driver(&meson_uart_driver);
> -}
> -
> -module_init(meson_uart_init);
> -module_exit(meson_uart_exit);
> +module_platform_driver(meson_uart_platform_driver);

Only pl010 uses this scheme, and I don't know why... if it works then it's ok for me.

Thanks,
Neil

>
> MODULE_AUTHOR("Carlo Caione <carlo@caione.org>");
> MODULE_DESCRIPTION("Amlogic Meson serial port driver");