Re: [PATCH V6 2/2] serial: exar: Add RS-485 support for Sealevel XR17V35X based cards

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Sep 14, 2023 at 04:52:21PM -0400, Matthew Howell wrote:
> From: Matthew Howell <matthew.howell@sealevel.com>
> 
> Sealevel XR17V35X based cards utilize DTR to control RS-485 Enable, but 
> the current implementation of 8250_exar uses RTS for the 
> auto-RS485-Enable mode of the XR17V35X UARTs. This patch implements DTR 
> Auto-RS485 on Sealevel cards.

You have trailing whitespace in your commit log :(

Please fix your editor to not do this.

> Link: https://lore.kernel.org/all/24b88a50-9c53-82ba-84d1-292c74c81981@sealevel.com/T/

This is not needed, don't link to older emails, that can be done on a
0/X message if you really want one.

> Signed-off-by: Matthew Howell <matthew.howell@sealevel.com>
> ---
> V5->V6
> Split ret in sealevel_rs485_config
> V4->V5
> Fixed typo in commit message
> Split readb and writeb into multiple lines/variables
> Removed "store original LCR" since it was clear from code
> Various small fixes to tabs and whitespace
> 
> diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
> index 3886f78ecbbf..34f0e18c7ad8 100644
> --- a/drivers/tty/serial/8250/8250_exar.c
> +++ b/drivers/tty/serial/8250/8250_exar.c
> @@ -78,6 +78,9 @@
> 
>  #define UART_EXAR_RS485_DLY(x)	((x) << 4)
> 
> +#define UART_EXAR_DLD				0x02 /* Divisor Fractional */
> +#define UART_EXAR_DLD_485_POLARITY	0x80 /* RS-485 Enable Signal Polarity */

Why are these values not lined up?

>  /*
>   * IOT2040 MPIO wiring semantics:
>   *
> @@ -439,6 +442,41 @@ static int generic_rs485_config(struct uart_port *port, struct ktermios *termios
>  	return 0;
>  }
> 
> +static int sealevel_rs485_config(struct uart_port *port, struct ktermios *termios,
> +				struct serial_rs485 *rs485)
> +{
> +	u8 __iomem *p = port->membase;
> +	u8 old_lcr;
> +	u8 efr;
> +	u8 dld;
> +
> +	generic_rs485_config(port, termios, rs485);

Shouldn't you check the return value of this function?

Yes, today it can't fail, but you don't know that will really be the
case, so please fix this.

thanks,

greg k-h