Re: [PATCH V1 1/4] usb: serial: f81534: add high baud rate support

[Johan Hovold <johan@kernel.org>]

On Thu, Nov 16, 2017 at 03:46:06PM +0800, Ji-Ze Hong (Peter Hong) wrote:
> The F81532/534 had 4 clocksource 1.846/18.46/14.77/24MHz and baud rates can
> be up to 1.5Mbits with 24MHz.
> 
> F81532/534 Clock register (offset +08h)
> 
> Bit0:	UART Enable (always on)
> Bit2-1:	Clock source selector
> 			00: 1.846MHz.
> 			01: 18.46MHz.
> 			10: 24MHz.
> 			11: 14.77MHz.
> 
> Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
> ---
>  drivers/usb/serial/f81534.c | 84 ++++++++++++++++++++++++++++++++++++---------
>  1 file changed, 68 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/usb/serial/f81534.c b/drivers/usb/serial/f81534.c
> index cb8214860192..76c676ef5f0d 100644
> --- a/drivers/usb/serial/f81534.c
> +++ b/drivers/usb/serial/f81534.c
> @@ -45,6 +45,7 @@
>  #define F81534_MODEM_CONTROL_REG	(0x04 + F81534_UART_BASE_ADDRESS)
>  #define F81534_LINE_STATUS_REG		(0x05 + F81534_UART_BASE_ADDRESS)
>  #define F81534_MODEM_STATUS_REG		(0x06 + F81534_UART_BASE_ADDRESS)
> +#define F81534_CLOCK_REG		(0x08 + F81534_UART_BASE_ADDRESS)
>  #define F81534_CONFIG1_REG		(0x09 + F81534_UART_BASE_ADDRESS)
>  
>  #define F81534_DEF_CONF_ADDRESS_START	0x3000
> @@ -61,7 +62,7 @@
>  
>  /* Default URB timeout for USB operations */
>  #define F81534_USB_MAX_RETRY		10
> -#define F81534_USB_TIMEOUT		1000
> +#define F81534_USB_TIMEOUT		2000

You need to at least mention in the commit message why this is needed.

>  #define F81534_SET_GET_REGISTER		0xA0
>  
>  #define F81534_NUM_PORT			4
> @@ -100,7 +101,6 @@
>  #define F81534_CMD_READ			0x03
>  
>  #define F81534_DEFAULT_BAUD_RATE	9600
> -#define F81534_MAX_BAUDRATE		115200
>  
>  #define F81534_PORT_CONF_DISABLE_PORT	BIT(3)
>  #define F81534_PORT_CONF_NOT_EXIST_PORT	BIT(7)
> @@ -110,6 +110,22 @@
>  #define F81534_1X_RXTRIGGER		0xc3
>  #define F81534_8X_RXTRIGGER		0xcf
>  
> +/*
> + * F81532/534 Clock registers (offset +08h)
> + *
> + * Bit0:	UART Enable (always on)
> + * Bit2-1:	Clock source selector
> + *			00: 1.846MHz.
> + *			01: 18.46MHz.
> + *			10: 24MHz.
> + *			11: 14.77MHz.
> + */
> +
> +#define F81534_CLK_1_846_MHZ		BIT(0)
> +#define F81534_CLK_18_46_MHZ		(BIT(0) | BIT(1))
> +#define F81534_CLK_24_MHZ		(BIT(0) | BIT(2))
> +#define F81534_CLK_14_77_MHZ		(BIT(0) | BIT(1) | BIT(2))

Use a separate define for the enable bit.

> +
>  static const struct usb_device_id f81534_id_table[] = {
>  	{ USB_DEVICE(FINTEK_VENDOR_ID_1, FINTEK_DEVICE_ID) },
>  	{ USB_DEVICE(FINTEK_VENDOR_ID_2, FINTEK_DEVICE_ID) },
> @@ -133,6 +149,7 @@ struct f81534_port_private {
>  	struct usb_serial_port *port;
>  	unsigned long tx_empty;
>  	spinlock_t msr_lock;
> +	u32 baud_base;
>  	u8 shadow_mcr;
>  	u8 shadow_lcr;
>  	u8 shadow_msr;
> @@ -464,13 +481,51 @@ static u32 f81534_calc_baud_divisor(u32 baudrate, u32 clockrate)
>  	return DIV_ROUND_CLOSEST(clockrate, baudrate);
>  }
>  
> -static int f81534_set_port_config(struct usb_serial_port *port, u32 baudrate,
> -					u8 lcr)
> +static int f81534_set_port_config(struct usb_serial_port *port,
> +		struct tty_struct *tty, u32 baudrate, u32 old_baudrate, u8 lcr)
>  {
>  	struct f81534_port_private *port_priv = usb_get_serial_port_data(port);
>  	u32 divisor;
>  	int status;
> +	int idx;
>  	u8 value;
> +	static u32 const baudrate_table[] = {115200, 921600, 1152000,
> +			1500000};
> +	static u8 const clock_table[] = {F81534_CLK_1_846_MHZ,
> +			F81534_CLK_14_77_MHZ, F81534_CLK_18_46_MHZ,
> +			F81534_CLK_24_MHZ};
> +
> +	do {
> +		for (idx = 0; idx < ARRAY_SIZE(baudrate_table); ++idx) {
> +			if (baudrate <= baudrate_table[idx] &&
> +					baudrate_table[idx] % baudrate == 0)
> +				break;
> +		}
> +
> +		/* Found acceptable baud rate */
> +		if (idx != ARRAY_SIZE(baudrate_table))
> +			break;
> +
> +		if (baudrate == old_baudrate &&
> +				old_baudrate != F81534_DEFAULT_BAUD_RATE)
> +			old_baudrate = F81534_DEFAULT_BAUD_RATE;
> +
> +		dev_warn(&port->dev,
> +				"baudrate: %d not supported, change to: %d\n",
> +				baudrate, old_baudrate);

No need to warn here as you report back the chosen speed in the termios.

> +
> +		baudrate = old_baudrate;
> +		tty_encode_baud_rate(tty, baudrate, baudrate);
> +
> +	} while (1);

This looks scary. Try to clean it up by adding helper function to
determine the base.

> +
> +	port_priv->baud_base = baudrate_table[idx];
> +	status = f81534_set_port_register(port, F81534_CLOCK_REG,
> +			clock_table[idx]);
> +	if (status) {
> +		dev_err(&port->dev, "CLOCK_REG setting failed\n");
> +		return status;
> +	}

I suggest you add a shadow clock register which keeps the enable bit
set. This should allow for a cleaner implementation of the auto-RTS
handling in later patches.

>  
>  	if (baudrate <= 1200)
>  		value = F81534_1X_RXTRIGGER;	/* 128 FIFO & TL: 1x */
> @@ -486,7 +541,7 @@ static int f81534_set_port_config(struct usb_serial_port *port, u32 baudrate,
>  	if (baudrate <= 1200)
>  		value = UART_FCR_TRIGGER_1 | UART_FCR_ENABLE_FIFO; /* TL: 1 */
>  	else
> -		value = UART_FCR_R_TRIG_11 | UART_FCR_ENABLE_FIFO; /* TL: 14 */
> +		value = UART_FCR_TRIGGER_8 | UART_FCR_ENABLE_FIFO; /* TL: 8 */

This should probably go in it's own patch, or at least be mentioned in
the commit message.

Johan