Re: [PATCH 4/6] serial: 8250_bcm2835aux: Allocate uart_8250_port on stack

[Matthias Brugger <mbrugger@suse.com>]

On 16/01/2020 13:14, Lukas Wunner wrote:
> The bcm2835aux UART driver stores a struct uart_8250_port in its private
> data even though it's only passed once to serial8250_register_8250_port()
> (which copies all relevant data) and becomes obsolete afterwards.
> Allocate the struct on the stack instead for simplicity and to conserve
> memory.
> 
> The driver also initializes a spinlock in the struct which is never used.
> Drop that as well.
> 
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> Cc: Martin Sperl <kernel@martin.sperl.org>

Reviewed-by: Matthias Brugger <mbrugger@suse.com>

> ---
>  drivers/tty/serial/8250/8250_bcm2835aux.c | 33 +++++++++++------------
>  1 file changed, 15 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c
> index fb850d0ad643..f03d38e7c3a7 100644
> --- a/drivers/tty/serial/8250/8250_bcm2835aux.c
> +++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
> @@ -17,13 +17,13 @@
>  #include "8250.h"
>  
>  struct bcm2835aux_data {
> -	struct uart_8250_port uart;
>  	struct clk *clk;
>  	int line;
>  };
>  
>  static int bcm2835aux_serial_probe(struct platform_device *pdev)
>  {
> +	struct uart_8250_port up = { };
>  	struct bcm2835aux_data *data;
>  	struct resource *res;
>  	int ret;
> @@ -34,17 +34,14 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  
>  	/* initialize data */
> -	spin_lock_init(&data->uart.port.lock);
> -	data->uart.capabilities = UART_CAP_FIFO | UART_CAP_MINI;
> -	data->uart.port.dev = &pdev->dev;
> -	data->uart.port.regshift = 2;
> -	data->uart.port.type = PORT_16550;
> -	data->uart.port.iotype = UPIO_MEM;
> -	data->uart.port.fifosize = 8;
> -	data->uart.port.flags = UPF_SHARE_IRQ |
> -				UPF_FIXED_PORT |
> -				UPF_FIXED_TYPE |
> -				UPF_SKIP_TEST;
> +	up.capabilities = UART_CAP_FIFO | UART_CAP_MINI;
> +	up.port.dev = &pdev->dev;
> +	up.port.regshift = 2;
> +	up.port.type = PORT_16550;
> +	up.port.iotype = UPIO_MEM;
> +	up.port.fifosize = 8;
> +	up.port.flags = UPF_SHARE_IRQ | UPF_FIXED_PORT | UPF_FIXED_TYPE |
> +			UPF_SKIP_TEST;
>  
>  	/* get the clock - this also enables the HW */
>  	data->clk = devm_clk_get(&pdev->dev, NULL);
> @@ -59,7 +56,7 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
>  	ret = platform_get_irq(pdev, 0);
>  	if (ret < 0)
>  		return ret;
> -	data->uart.port.irq = ret;
> +	up.port.irq = ret;
>  
>  	/* map the main registers */
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> @@ -67,15 +64,15 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
>  		dev_err(&pdev->dev, "memory resource not found");
>  		return -EINVAL;
>  	}
> -	data->uart.port.membase = devm_ioremap_resource(&pdev->dev, res);
> -	ret = PTR_ERR_OR_ZERO(data->uart.port.membase);
> +	up.port.membase = devm_ioremap_resource(&pdev->dev, res);
> +	ret = PTR_ERR_OR_ZERO(up.port.membase);
>  	if (ret)
>  		return ret;
>  
>  	/* Check for a fixed line number */
>  	ret = of_alias_get_id(pdev->dev.of_node, "serial");
>  	if (ret >= 0)
> -		data->uart.port.line = ret;
> +		up.port.line = ret;
>  
>  	/* enable the clock as a last step */
>  	ret = clk_prepare_enable(data->clk);
> @@ -90,10 +87,10 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
>  	 * so we have to multiply the actual clock by 2
>  	 * to get identical baudrates.
>  	 */
> -	data->uart.port.uartclk = clk_get_rate(data->clk) * 2;
> +	up.port.uartclk = clk_get_rate(data->clk) * 2;
>  
>  	/* register the port */
> -	ret = serial8250_register_8250_port(&data->uart);
> +	ret = serial8250_register_8250_port(&up);
>  	if (ret < 0) {
>  		if (ret != -EPROBE_DEFER)
>  			dev_err(&pdev->dev,
>