linux-kernel - Re: [PATCH v1 3/5] tty: serial: meson: apply ttyS devname instead of ttyAML for new SoCs

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Date:   Tue, 4 Jul 2023 16:42:39 +0200
From:   neil.armstrong@...aro.org
To:     Dmitry Rokosov <ddrokosov@...rdevices.ru>,
        gregkh@...uxfoundation.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        jbrunet@...libre.com, jirislaby@...nel.org, khilman@...libre.com,
        martin.blumenstingl@...glemail.com
Cc:     kelvin.zhang@...ogic.com, xianwei.zhao@...ogic.com,
        kernel@...rdevices.ru, rockosov@...il.com,
        linux-amlogic@...ts.infradead.org, linux-serial@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 3/5] tty: serial: meson: apply ttyS devname instead of
 ttyAML for new SoCs

On 04/07/2023 15:59, Dmitry Rokosov wrote:
> It is worth noting that the devname ttyS is a widely recognized tty name
> and is commonly used by many uart device drivers. Given the established
> usage and compatibility concerns, it may not be feasible to change the
> devname for older SoCs. However, for new definitions, it is acceptable
> and even recommended to use a new devname to help ensure clarity and
> avoid any potential conflicts on lower or upper software levels. In
> addition, modify the meson_uart_dt match data for g12a, a1, and s4 to
> their appropriate values to ensure proper devname values and
> functionality.

I'm not confident about modifying a global struct from a probe,
I think you should add a separate meson_uart_driver/meson_serial_console couple
with ttyS instead of ttyAML, refer to the right uart_driver in meson_uart_data
and in probe() register it and pass it to uart_add_one_port().

Neil

> 
> For more information please refer to IRC discussion at [1].
> 
> Links:
>      [1]: https://libera.irclog.whitequark.org/linux-amlogic/2023-07-03
> 
> Signed-off-by: Dmitry Rokosov <ddrokosov@...rdevices.ru>
> ---
>   drivers/tty/serial/meson_uart.c | 33 +++++++++++++++++++++++++++++++--
>   1 file changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
> index 87c0eb5f2dba..361f9326b527 100644
> --- a/drivers/tty/serial/meson_uart.c
> +++ b/drivers/tty/serial/meson_uart.c
> @@ -82,6 +82,7 @@ static struct uart_driver meson_uart_driver;
>   static struct uart_port *meson_ports[AML_UART_PORT_NUM];
>   
>   struct meson_uart_data {
> +	const char *dev_name;
>   	bool has_xtal_div2;
>   };
>   
> @@ -683,6 +684,7 @@ static int meson_uart_probe_clocks(struct platform_device *pdev,
>   
>   static int meson_uart_probe(struct platform_device *pdev)
>   {
> +	const struct meson_uart_data *priv_data;
>   	struct resource *res_mem;
>   	struct uart_port *port;
>   	u32 fifosize = 64; /* Default is 64, 128 for EE UART_0 */
> @@ -729,6 +731,18 @@ static int meson_uart_probe(struct platform_device *pdev)
>   	if (ret)
>   		return ret;
>   
> +	priv_data = device_get_match_data(&pdev->dev);
> +
> +	if (priv_data) {
> +		struct console *cons = meson_uart_driver.cons;
> +
> +		meson_uart_driver.dev_name = priv_data->dev_name;
> +
> +		if (cons)
> +			strscpy(cons->name, priv_data->dev_name,
> +				sizeof(cons->name));
> +	}
> +
>   	if (!meson_uart_driver.state) {
>   		ret = uart_register_driver(&meson_uart_driver);
>   		if (ret)
> @@ -748,7 +762,7 @@ static int meson_uart_probe(struct platform_device *pdev)
>   	port->x_char = 0;
>   	port->ops = &meson_uart_ops;
>   	port->fifosize = fifosize;
> -	port->private_data = (void *)device_get_match_data(&pdev->dev);
> +	port->private_data = (void *)priv_data;
>   
>   	meson_ports[pdev->id] = port;
>   	platform_set_drvdata(pdev, port);
> @@ -780,6 +794,17 @@ static int meson_uart_remove(struct platform_device *pdev)
>   }
>   
>   static struct meson_uart_data meson_g12a_uart_data = {
> +	.dev_name = "ttyAML",
> +	.has_xtal_div2 = true,
> +};
> +
> +static struct meson_uart_data meson_a1_uart_data = {
> +	.dev_name = "ttyS",
> +	.has_xtal_div2 = false,
> +};
> +
> +static struct meson_uart_data meson_s4_uart_data = {
> +	.dev_name = "ttyS",
>   	.has_xtal_div2 = true,
>   };
>   
> @@ -794,7 +819,11 @@ static const struct of_device_id meson_uart_dt_match[] = {
>   	},
>   	{
>   		.compatible = "amlogic,meson-s4-uart",
> -		.data = (void *)&meson_g12a_uart_data,
> +		.data = (void *)&meson_s4_uart_data,
> +	},
> +	{
> +		.compatible = "amlogic,meson-a1-uart",
> +		.data = (void *)&meson_a1_uart_data,
>   	},
>   	{ /* sentinel */ },
>   };