On Sun, Sep 16, 2018 at 07:58:47PM +0200, Karoly Pados wrote:
> This patch allows using the CBUS pins of FT-X devices as GPIO in CBUS
> bitbanging mode. There is no conflict between the GPIO and VCP
> functionality in this mode. Tested on FT230X and FT231X.
>
> As there is no way to request the current CBUS register configuration
> from the device, all CBUS pins are set to a known state when the first
> GPIO is requested. This allows using libftdi to set the GPIO pins
> before loading this module for UART functionality, a behavior that
> existing applications might be relying upon (though no specific case
> is known to the authors of this patch).
>
> Signed-off-by: Karoly Pados <pados@xxxxxxxx>
> ---
> Changelog:
> - v2: Fix compile error when CONFIG_GPIOLIB is not defined.
> - v3: Incorporate review feedback.
> - v4: Include linux/gpio/driver.h unconditionally.
> Replace and invert gpio_input with gpio_output.
> Make ftdi_gpio_direction_get return 0/1.
> Change dev_err msg in ftdi_set_bitmode_req.
> Change formatting of error checking in ftdi_gpio_get.
> Drop dev_err in ftdi_gpio_set.
> Remove some line breaks and empty lines.
> Change error handling in ftdi_read_eeprom (and adjust caller).
> Replace SIO->FTX in FTDI_SIO_CBUS_MUX_GPIO macro name.
Really nice job with this; looks nice and clean over all. Just a few
comments below.
> +static int ftx_gpioconf_init(struct usb_serial_port *port)
> +{
> + struct ftdi_private *priv = usb_get_serial_port_data(port);
> + struct usb_serial *serial = port->serial;
> + const u16 cbus_cfg_addr = 0x1a;
> + const u16 cbus_cfg_size = 8;
Looks like you only need to read four bytes.
> + u8 *cbus_cfg_buf;
> + int result;
> + u8 i;
> +
> + /* Read a part of device EEPROM */
> + cbus_cfg_buf = kmalloc(cbus_cfg_size, GFP_KERNEL);
> + if (!cbus_cfg_buf)
> + return -ENOMEM;
> +
> + result = ftdi_read_eeprom(serial, cbus_cfg_buf,
> + cbus_cfg_addr, cbus_cfg_size);
> + if (result != 0)
result < 0 would be more informative here.
> + goto out_free;
> +
> + /* Chip-type guessing logic based on libftdi. */
> + priv->gc.ngpio = 4; /* FT230X, FT231X */
> + if (le16_to_cpu(serial->dev->descriptor.bcdDevice) != 0x1000)
> + priv->gc.ngpio = 1; /* FT234XD */
As I mentioned in my last mail: I've asked FTDI about this, but I fear
that FTX234XD has bcdDevice 0x1000 and we may need to just always
register all four pins after all.
> + /* Determine which pins are configured for CBUS bitbanging */
> + priv->gpio_altfunc = 0xff;
> + for (i = 0; i < priv->gc.ngpio; ++i) {
> + if (cbus_cfg_buf[i] == FTDI_FTX_CBUS_MUX_GPIO)
> + priv->gpio_altfunc &= ~BIT(i);
> + }
> +
> +out_free:
> + kfree(cbus_cfg_buf);
> +
> + return result;
> +}
> +static void ftdi_gpio_remove(struct usb_serial_port *port)
> +{
> + struct ftdi_private *priv = usb_get_serial_port_data(port);
> +
> + if (priv->gpio_used) {
> + /* Remark: Exiting CBUS-mode does not reset pin states too */
> + ftdi_exit_cbus_mode(port);
> + priv->gpio_used = false;
> + }
This should go after deregistration or we have a tiny race window here.
> + if (priv->gpio_registered) {
> + gpiochip_remove(&priv->gc);
> + priv->gpio_registered = false;
> + }
> +}
> diff --git a/drivers/usb/serial/ftdi_sio.h b/drivers/usb/serial/ftdi_sio.h
> index dcd0b6e05baf..6856ccdac9b4 100644
> --- a/drivers/usb/serial/ftdi_sio.h
> +++ b/drivers/usb/serial/ftdi_sio.h
> @@ -35,7 +35,10 @@
> #define FTDI_SIO_SET_EVENT_CHAR 6 /* Set the event character */
> #define FTDI_SIO_SET_ERROR_CHAR 7 /* Set the error character */
> #define FTDI_SIO_SET_LATENCY_TIMER 9 /* Set the latency timer */
> -#define FTDI_SIO_GET_LATENCY_TIMER 10 /* Get the latency timer */
> +#define FTDI_SIO_GET_LATENCY_TIMER 0x0a /* Get the latency timer */
> +#define FTDI_SIO_SET_BITMODE 0x0b /* Set GPIO mode */
Nit: "Set bitbang mode", I think would be more correct here as this
request is also used to configure the asynchronous bitbang mode, etc.
Thanks,
Johan
