Re: [PATCH V2 5/7] USB: serial: f81232: Set F81534A serial port with RS232 mode

From: Johan Hovold <johan@kernel.org>
To: "Ji-Ze Hong (Peter Hong)" <hpeter@gmail.com>
Cc: johan@kernel.org, gregkh@linuxfoundation.org,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	peter_hong@fintek.com.tw,
	"Ji-Ze Hong (Peter Hong)" <hpeter+linux_kernel@gmail.com>
Subject: Re: [PATCH V2 5/7] USB: serial: f81232: Set F81534A serial port with RS232 mode
Date: Wed, 23 Oct 2019 13:53:00 +0200	[thread overview]
Message-ID: <20191023115300.GU24768@localhost> (raw)
In-Reply-To: <20190923022449.10952-6-hpeter+linux_kernel@gmail.com>

On Mon, Sep 23, 2019 at 10:24:47AM +0800, Ji-Ze Hong (Peter Hong) wrote:
> The Fintek F81532A/534A/535/536 is USB-to-2/4/8/12 serial ports device
> and the serial ports are default disabled. Each port contains max 3 pins
> GPIO and the 3 pins are default pull high with input mode.
> 
> When the serial port had activated (running probe()), we'll transform the
> 3 pins from GPIO function publicly to control Tranceiver privately use.

I'm not sure I understand what you're saying here.

> We'll default set to 0/0/1 for control transceiver to RS232 mode.
> 
> Otherwise, If the serial port is not active, the 3 pins is in GPIO mode
> and controlled by global GPIO device with VID/PID: 2c42/16f8.

Does this mean that you can control the three GPIOs either through the
serial device or through the gpio-control device (which are two separate
USB devices)?

> Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
> ---
>  drivers/usb/serial/f81232.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
> index 36a17aedc2ae..01cb5a5ea1d2 100644
> --- a/drivers/usb/serial/f81232.c
> +++ b/drivers/usb/serial/f81232.c
> @@ -96,6 +96,15 @@ MODULE_DEVICE_TABLE(usb, all_serial_id_table);
>  #define F81534A_TRIGGER_MULTPILE_4X	BIT(3)
>  #define F81534A_FIFO_128BYTE		(BIT(1) | BIT(0))
>  
> +/* Serial port self GPIO control, 2bytes [control&output data][input data] */
> +#define F81534A_GPIO_REG		0x10e
> +#define F81534A_GPIO_MODE2_DIR		BIT(6) /* 1: input, 0: output */
> +#define F81534A_GPIO_MODE1_DIR		BIT(5)
> +#define F81534A_GPIO_MODE0_DIR		BIT(4)
> +#define F81534A_GPIO_MODE2_OUTPUT	BIT(2)
> +#define F81534A_GPIO_MODE1_OUTPUT	BIT(1)
> +#define F81534A_GPIO_MODE0_OUTPUT	BIT(0)
> +
>  struct f81232_private {
>  	struct mutex lock;
>  	u8 modem_control;
> @@ -866,6 +875,14 @@ static int f81232_port_probe(struct usb_serial_port *port)
>  
>  static int f81534a_port_probe(struct usb_serial_port *port)
>  {
> +	int status;
> +
> +	/* tri-state with pull-high, default RS232 Mode */
> +	status = f81232_set_register(port, F81534A_GPIO_REG,
> +					F81534A_GPIO_MODE2_DIR);
> +	if (status)
> +		return status;

Ok, so you reset the tranceiver config on every probe.

Are the three GPIOs always connected to one particular tranceiver, or
are they truly general purpose?

In the latter case, it doesn't seem like a good idea to drive pins 0
and 1 low here as you have know idea what they're used for.

> +
>  	return f81232_port_probe(port);
>  }

Johan