Re: [PATCH v2] serial: 8250: Add Nuvoton NPCM UART

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Feb 15, 2018 at 12:47:20PM +1030, Joel Stanley wrote:
> The Nuvoton UART is almost compatible with the 8250 driver when probed
> via the 8250_of driver, however it requires some extra configuration
> at startup.
> 
> Signed-off-by: Joel Stanley <joel@jms.id.au>
> Reviewed-by: Rob Herring <robh@kernel.org>
> ---
> v2:
>  Remove redundant whitespace
>  Use port number 40 to fill in a gap
> 
>  Documentation/devicetree/bindings/serial/8250.txt |  1 +
>  drivers/tty/serial/8250/8250_of.c                 |  1 +
>  drivers/tty/serial/8250/8250_port.c               | 29 +++++++++++++++++++++++
>  include/uapi/linux/serial_core.h                  |  3 +++
>  include/uapi/linux/serial_reg.h                   |  5 ++++
>  5 files changed, 39 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/serial/8250.txt b/Documentation/devicetree/bindings/serial/8250.txt
> index dad3b2ec66d4..aeb6db4e35c3 100644
> --- a/Documentation/devicetree/bindings/serial/8250.txt
> +++ b/Documentation/devicetree/bindings/serial/8250.txt
> @@ -24,6 +24,7 @@ Required properties:
>  	- "ti,da830-uart"
>  	- "aspeed,ast2400-vuart"
>  	- "aspeed,ast2500-vuart"
> +	- "nuvoton,npcm750-uart"
>  	- "serial" if the port type is unknown.
>  - reg : offset and length of the register set for the device.
>  - interrupts : should contain uart interrupt.
> diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
> index 160b8906d9b9..9835b1c1cbe1 100644
> --- a/drivers/tty/serial/8250/8250_of.c
> +++ b/drivers/tty/serial/8250/8250_of.c
> @@ -316,6 +316,7 @@ static const struct of_device_id of_platform_serial_table[] = {
>  	{ .compatible = "mrvl,mmp-uart",
>  		.data = (void *)PORT_XSCALE, },
>  	{ .compatible = "ti,da830-uart", .data = (void *)PORT_DA830, },
> +	{ .compatible = "nuvoton,npcm750-uart", .data = (void *)PORT_NPCM, },
>  	{ /* end of list */ },
>  };
>  MODULE_DEVICE_TABLE(of, of_platform_serial_table);
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 1328c7e70108..a72222f8b005 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -293,6 +293,15 @@ static const struct serial8250_config uart_config[] = {
>  				  UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
>  		.flags		= UART_CAP_FIFO,
>  	},
> +	[PORT_NPCM] = {
> +		.name		= "Nuvoton 16550",
> +		.fifo_size	= 16,
> +		.tx_loadsz	= 16,
> +		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10 |
> +				  UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
> +		.rxtrig_bytes	= {1, 4, 8, 14},
> +		.flags		= UART_CAP_FIFO,
> +	},
>  };
>  
>  /* Uart divisor latch read */
> @@ -2140,6 +2149,15 @@ int serial8250_do_startup(struct uart_port *port)
>  				UART_DA830_PWREMU_MGMT_FREE);
>  	}
>  
> +	if (port->type == PORT_NPCM) {
> +		/*
> +		 * Nuvoton calls the scratch register 'UART_TOR' (timeout
> +		 * register). Enable it, and set TIOC (timeout interrupt
> +		 * comparator) to be 0x20 for correct operation.
> +		 */
> +		serial_port_out(port, UART_NPCM_TOR, UART_NPCM_TOIE | 0x20);
> +	}
> +
>  #ifdef CONFIG_SERIAL_8250_RSA
>  	/*
>  	 * If this is an RSA port, see if we can kick it up to the
> @@ -2462,6 +2480,15 @@ static unsigned int xr17v35x_get_divisor(struct uart_8250_port *up,
>  	return quot_16 >> 4;
>  }
>  
> +/* Nuvoton NPCM UARTs have a custom divisor calculation */
> +static unsigned int npcm_get_divisor(struct uart_8250_port *up,
> +		unsigned int baud)
> +{
> +	struct uart_port *port = &up->port;
> +
> +	return DIV_ROUND_CLOSEST(port->uartclk, 16 * baud + 2) - 2;
> +}
> +
>  static unsigned int serial8250_get_divisor(struct uart_8250_port *up,
>  					   unsigned int baud,
>  					   unsigned int *frac)
> @@ -2482,6 +2509,8 @@ static unsigned int serial8250_get_divisor(struct uart_8250_port *up,
>  		quot = 0x8002;
>  	else if (up->port.type == PORT_XR17V35X)
>  		quot = xr17v35x_get_divisor(up, baud, frac);
> +	else if (up->port.type == PORT_NPCM)
> +		quot = npcm_get_divisor(up, baud);
>  	else
>  		quot = uart_get_divisor(port, baud);
>  
> diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
> index 1c8413f93e3d..dce5f9dae121 100644
> --- a/include/uapi/linux/serial_core.h
> +++ b/include/uapi/linux/serial_core.h
> @@ -76,6 +76,9 @@
>  #define PORT_SUNZILOG	38
>  #define PORT_SUNSAB	39
>  
> +/* Nuvoton UART */
> +#define PORT_NPCM	40
> +
>  /* Intel EG20 */
>  #define PORT_PCH_8LINE	44
>  #define PORT_PCH_2LINE	45
> diff --git a/include/uapi/linux/serial_reg.h b/include/uapi/linux/serial_reg.h
> index be07b5470f4b..f82f3c869df9 100644
> --- a/include/uapi/linux/serial_reg.h
> +++ b/include/uapi/linux/serial_reg.h
> @@ -376,5 +376,10 @@
>  #define UART_ALTR_EN_TXFIFO_LW	0x01	/* Enable the TX FIFO Low Watermark */
>  #define UART_ALTR_TX_LOW	0x41	/* Tx FIFO Low Watermark */
>  
> +
> +/* Nuvoton NPCM timeout register */
> +#define UART_NPCM_TOR		7
> +#define UART_NPCM_TOIE		BIT(7)	/* Timeout Interrupt Enable */

Why is this needed in a userspace api file?  That feels very odd for
just a new device.  Please put this somewhere internal.

thanks,

greg k-h