Re: [PATCH 2/3] tty: serial: atmel: improve clock management

[Richard Genoud <richard.genoud@gmail.com>]

Hi,

Le 25/05/2022 à 15:37, Claudiu Beznea a écrit :
> atmel_port->clk was requested in atmel_init_port() (which is called only
> on probe path) only if atmel_port->clk was NULL. But atmel_port->clk is
> NULL on probing path. Thus don't check this. Along with this the clock is
> now requested with devm_clk_get() and the clock request has been moved in
> atmel_serial_probe() function to avoid disabling/re-enabling it on probe
> path for multiple times. All the checks of atmel_port->clk were removed
> along with clk_put() and atmel_port->clk = NULL. Now, on probing time the
> clock is enabled at the beginning and disabled at the end of probe. As
> atmel_console_setup() is called in the middle of probe and clock is
> already enabled at that time the clk_prepare_enable() in
> atmel_console_setup() has also been removed.
Could you split this patch into smaller steps ?
I think it will be easier to read and review.

> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
> ---
>   drivers/tty/serial/atmel_serial.c | 65 +++++++------------------------
>   1 file changed, 15 insertions(+), 50 deletions(-)
> 
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index 5c793a23dc54..2955b1012014 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -2501,24 +2501,7 @@ static int atmel_init_port(struct atmel_uart_port *atmel_port,
>   	if (ret)
>   		return ret;
>   
> -	/* for console, the clock could already be configured */
> -	if (!atmel_port->clk) {
> -		atmel_port->clk = clk_get(&mpdev->dev, "usart");
> -		if (IS_ERR(atmel_port->clk)) {
> -			ret = PTR_ERR(atmel_port->clk);
> -			atmel_port->clk = NULL;
> -			return ret;
> -		}
> -		ret = clk_prepare_enable(atmel_port->clk);
> -		if (ret) {
> -			clk_put(atmel_port->clk);
> -			atmel_port->clk = NULL;
> -			return ret;
> -		}
> -		port->uartclk = clk_get_rate(atmel_port->clk);
> -		clk_disable_unprepare(atmel_port->clk);
> -		/* only enable clock when USART is in use */
> -	}
> +	port->uartclk = clk_get_rate(atmel_port->clk);
>   
>   	/*
>   	 * Use TXEMPTY for interrupt when rs485 or ISO7816 else TXRDY or
> @@ -2640,10 +2623,6 @@ static int __init atmel_console_setup(struct console *co, char *options)
>   		return -ENODEV;
>   	}
>   
> -	ret = clk_prepare_enable(atmel_ports[co->index].clk);
> -	if (ret)
> -		return ret;
> -
Now, "int ret;" is unused, you can remove it.

>   	atmel_uart_writel(port, ATMEL_US_IDR, -1);
>   	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
>   	atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN);
> @@ -2889,14 +2868,23 @@ static int atmel_serial_probe(struct platform_device *pdev)
>   	atomic_set(&atmel_port->tasklet_shutdown, 0);
>   	spin_lock_init(&atmel_port->lock_suspended);
>   
> +	atmel_port->clk = devm_clk_get(&pdev->dev, "usart");
> +	if (IS_ERR(atmel_port->clk)) {
> +		ret = PTR_ERR(atmel_port->clk);
> +		goto err;
> +	}
> +	ret = clk_prepare_enable(atmel_port->clk);
> +	if (ret)
> +		goto err;
> +
>   	ret = atmel_init_port(atmel_port, pdev);
>   	if (ret)
> -		goto err_clear_bit;
> +		goto err_clk_disable_unprepare;
>   
>   	atmel_port->gpios = mctrl_gpio_init(&atmel_port->uart, 0);
>   	if (IS_ERR(atmel_port->gpios)) {
>   		ret = PTR_ERR(atmel_port->gpios);
> -		goto err_clear_bit;
> +		goto err_clk_disable_unprepare;
>   	}
>   
>   	if (!atmel_use_pdc_rx(&atmel_port->uart)) {
> @@ -2905,7 +2893,7 @@ static int atmel_serial_probe(struct platform_device *pdev)
>   				     sizeof(struct atmel_uart_char),
>   				     GFP_KERNEL);
>   		if (!data)
> -			goto err_alloc_ring;
> +			goto err_clk_disable_unprepare;
>   		atmel_port->rx_ring.buf = data;
>   	}
>   
> @@ -2915,26 +2903,9 @@ static int atmel_serial_probe(struct platform_device *pdev)
>   	if (ret)
>   		goto err_add_port;
>   
> -#ifdef CONFIG_SERIAL_ATMEL_CONSOLE
> -	if (uart_console(&atmel_port->uart)
> -			&& ATMEL_CONSOLE_DEVICE->flags & CON_ENABLED) {
> -		/*
> -		 * The serial core enabled the clock for us, so undo
> -		 * the clk_prepare_enable() in atmel_console_setup()
> -		 */
> -		clk_disable_unprepare(atmel_port->clk);
> -	}
> -#endif
> -
>   	device_init_wakeup(&pdev->dev, 1);
>   	platform_set_drvdata(pdev, atmel_port);
>   
> -	/*
> -	 * The peripheral clock has been disabled by atmel_init_port():
> -	 * enable it before accessing I/O registers
> -	 */
> -	clk_prepare_enable(atmel_port->clk);
> -
>   	if (rs485_enabled) {
>   		atmel_uart_writel(&atmel_port->uart, ATMEL_US_MR,
>   				  ATMEL_US_USMODE_NORMAL);
> @@ -2958,12 +2929,8 @@ static int atmel_serial_probe(struct platform_device *pdev)
>   err_add_port:
>   	kfree(atmel_port->rx_ring.buf);
>   	atmel_port->rx_ring.buf = NULL;
> -err_alloc_ring:
> -	if (!uart_console(&atmel_port->uart)) {
> -		clk_put(atmel_port->clk);
> -		atmel_port->clk = NULL;
> -	}
> -err_clear_bit:
> +err_clk_disable_unprepare:
> +	clk_disable_unprepare(atmel_port->clk);
>   	clear_bit(atmel_port->uart.line, atmel_ports_in_use);
>   err:
>   	return ret;
> @@ -2997,8 +2964,6 @@ static int atmel_serial_remove(struct platform_device *pdev)
>   
>   	clear_bit(port->line, atmel_ports_in_use);
>   
> -	clk_put(atmel_port->clk);
> -	atmel_port->clk = NULL;
>   	pdev->dev.of_node = NULL;
>   
>   	return ret;
Thanks !

Regards,
Richard