linux-kernel - Re: [PATCH] serial: 8250_bcm7271: improve bcm7271 8250 port

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Date:   Sat, 12 Aug 2023 12:50:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Justin Chen <justin.chen@...adcom.com>
Cc:     linux-serial@...r.kernel.org, opendmb@...il.com,
        Al Cooper <alcooperx@...il.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        John Ogness <john.ogness@...utronix.de>,
        Jiaqing Zhao <jiaqing.zhao@...ux.intel.com>,
        "open list:TTY LAYER" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial: 8250_bcm7271: improve bcm7271 8250 port

On Fri, Aug 11, 2023 at 03:14:01PM -0700, Justin Chen wrote:
> The 8250 bcm7271 UART is not a direct match to PORT_16550A. The
> Fifo is 32 and rxtrig values are {1, 8, 16, 30}. Create a PORT_BCM7271
> to better capture the HW CAPS.
> 
> Default the rxtrig level to 8.
> 
> Signed-off-by: Justin Chen <justin.chen@...adcom.com>
> ---
>  drivers/tty/serial/8250/8250_bcm7271.c | 4 +---
>  drivers/tty/serial/8250/8250_port.c    | 8 ++++++++
>  include/uapi/linux/serial_core.h       | 3 +++
>  3 files changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_bcm7271.c b/drivers/tty/serial/8250/8250_bcm7271.c
> index d4b05d7ad9e8..aa5aff046756 100644
> --- a/drivers/tty/serial/8250/8250_bcm7271.c
> +++ b/drivers/tty/serial/8250/8250_bcm7271.c
> @@ -1042,7 +1042,7 @@ static int brcmuart_probe(struct platform_device *pdev)
>  	dev_dbg(dev, "DMA is %senabled\n", priv->dma_enabled ? "" : "not ");
>  
>  	memset(&up, 0, sizeof(up));
> -	up.port.type = PORT_16550A;
> +	up.port.type = PORT_BCM7271;
>  	up.port.uartclk = clk_rate;
>  	up.port.dev = dev;
>  	up.port.mapbase = mapbase;
> @@ -1056,8 +1056,6 @@ static int brcmuart_probe(struct platform_device *pdev)
>  		| UPF_FIXED_PORT | UPF_FIXED_TYPE;
>  	up.port.dev = dev;
>  	up.port.private_data = priv;
> -	up.capabilities = UART_CAP_FIFO | UART_CAP_AFE;
> -	up.port.fifosize = 32;
>  
>  	/* Check for a fixed line number */
>  	ret = of_alias_get_id(np, "serial");
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 16aeb1420137..a6259a264041 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -322,6 +322,14 @@ static const struct serial8250_config uart_config[] = {
>  		.rxtrig_bytes   = {2, 66, 130, 194},
>  		.flags          = UART_CAP_FIFO,
>  	},
> +	[PORT_BCM7271] = {
> +		.name		= "bcm7271_uart",
> +		.fifo_size	= 32,
> +		.tx_loadsz	= 32,
> +		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01,
> +		.rxtrig_bytes	= {1, 8, 16, 30},
> +		.flags		= UART_CAP_FIFO | UART_CAP_AFE
> +	},
>  };
>  
>  /* Uart divisor latch read */
> diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
> index 281fa286555c..369f845a3d1d 100644
> --- a/include/uapi/linux/serial_core.h
> +++ b/include/uapi/linux/serial_core.h
> @@ -279,4 +279,7 @@
>  /* Sunplus UART */
>  #define PORT_SUNPLUS	123
>  
> +/* Broadcom 7271 UART */
> +#define PORT_BCM7271    124

Why is this new id required?  What in userspace is going to use it and
why can't the generic value be used instead?

thanks,

greg k-h