[PATCH v4 13/13] USB: ch341: implement tx_empty callback

Grigori Goronzy
2016-04-15T21:15:36Z

The status bit was found with USB captures of the Windows driver and
some luck. Tested on CH340G and CH341A.

v2: unify general status definitions

Signed-off-by: Grigori Goronzy <greg@chown.ath.cx>
---
drivers/usb/serial/ch341.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index 78adce7..12a430c 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -39,9 +39,6 @@
/* third irq byte base 0x94 + below */
/* fourth irq byte normally 0xee */

-/* second interrupt byte */
-#define CH341_MULT_STAT 0x04 /* multiple status since last interrupt event */
-
/* status returned in third interrupt answer byte, inverted in data
from irq */
#define CH341_BIT_CTS 0x01
@@ -81,6 +78,10 @@
#define CH341_LCR_CS6 0x01
#define CH341_LCR_CS5 0x00

+/* General status from register 0x07 and second interrupt byte */
+#define CH341_STATUS_TXBUSY 0x01
+#define CH341_STATUS_MULTI 0x04
+
static const struct usb_device_id id_table[] = {
{ USB_DEVICE(0x4348, 0x5523) },
{ USB_DEVICE(0x1a86, 0x7523) },
@@ -94,6 +95,7 @@ struct ch341_private {
unsigned baud_rate; /* set baud rate */
u8 line_control; /* set line control value RTS/DTR */
u8 line_status; /* active status of modem control inputs */
+ u8 uart_status; /* generic UART status bits */
};

static void ch341_set_termios(struct tty_struct *tty,
@@ -184,7 +186,8 @@ static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
if (r == 2) {
r = 0;
spin_lock_irqsave(&priv->lock, flags);
- priv->line_status = (~(*buffer)) & CH341_BITS_MODEM_STAT;
+ priv->line_status = (~buffer[0]) & CH341_BITS_MODEM_STAT;
+ priv->uart_status = buffer[1];
spin_unlock_irqrestore(&priv->lock, flags);
} else {
r = -EPROTO;
@@ -195,6 +198,18 @@ out:
return r;
}

+static bool ch341_tx_empty(struct usb_serial_port *port)
+{
+ int r;
+ struct ch341_private *priv = usb_get_serial_port_data(port);
+
+ r = ch341_get_status(port->serial->dev, priv);
+ if (r < 0)
+ return true;
+
+ return !(priv->uart_status & CH341_STATUS_TXBUSY);
+}
+
/* -------------------------------------------------------------------------- */

static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
@@ -493,7 +508,7 @@ static void ch341_update_line_status(struct usb_serial_port *port,
priv->line_status = status;
spin_unlock_irqrestore(&priv->lock, flags);

- if (data[1] & CH341_MULT_STAT)
+ if (data[1] & CH341_STATUS_MULTI)
dev_dbg(&port->dev, "Multiple status change\n");

if (!delta)
@@ -599,6 +614,7 @@ static struct usb_serial_driver ch341_device = {
.carrier_raised = ch341_carrier_raised,
.close = ch341_close,
.set_termios = ch341_set_termios,
+ .tx_empty = ch341_tx_empty,
.break_ctl = ch341_break_ctl,
.tiocmget = ch341_tiocmget,
.tiocmset = ch341_tiocmset,
--
1.9.1