Some CH341 devices appear to require the use of the init vendor command
to set the baud rate and line-control register. Specifically, while
using direct register updates for speed and LCR seem to update those
settings correctly, not using the init command causes received data to
be buffered until a full endpoint-size packet (32 bytes) have been
received (i.e. the init command has some undocumented side-effect we
need).
On the other hand, some CH340 devices have been reported to require the
use of direct register manipulations to set the line speed, while not
suffering from the above mentioned buffering effect.
Let's use the init vendor command only for CH341 devices to be able to
support also such (quirky?) CH340 devices.
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
---
drivers/usb/serial/ch341.c | 46 +++++++++++++++++++++++++++++++++++-----------
1 file changed, 35 insertions(+), 11 deletions(-)
diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index e1dd096106d1..05fd32a52048 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -82,10 +82,12 @@
#define CH341_LCR_CS6 0x01
#define CH341_LCR_CS5 0x00
+#define CH341_QUIRK_INIT BIT(0)
+
static const struct usb_device_id id_table[] = {
{ USB_DEVICE(0x4348, 0x5523) },
{ USB_DEVICE(0x1a86, 0x7523) },
- { USB_DEVICE(0x1a86, 0x5523) },
+ { USB_DEVICE(0x1a86, 0x5523), .driver_info = CH341_QUIRK_INIT },
{ },
};
MODULE_DEVICE_TABLE(usb, id_table);
@@ -96,6 +98,8 @@ struct ch341_private {
u8 line_control; /* set line control value RTS/DTR */
u8 line_status; /* active status of modem control inputs */
u8 lcr;
+
+ unsigned long quirks;
};
static void ch341_set_termios(struct tty_struct *tty,
@@ -148,7 +152,7 @@ static int ch341_control_in(struct usb_device *dev,
return 0;
}
-static int ch341_init_set_baudrate(struct usb_device *dev,
+static int ch341_set_baudrate_lcr(struct usb_device *dev,
struct ch341_private *priv, unsigned ctrl)
{
short a;
@@ -172,9 +176,23 @@ static int ch341_init_set_baudrate(struct usb_device *dev,
factor = 0x10000 - factor;
a = (factor & 0xff00) | divisor;
- /* 0x9c is "enable SFR_UART Control register and timer" */
- r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT,
- 0x9c | (ctrl << 8), a | 0x80);
+ /*
+ * Some CH341 devices require us to use the init vendor command to set
+ * the baud rate and LCR.
+ */
+ if (priv->quirks & CH341_QUIRK_INIT) {
+ /* 0x9c is "enable SFR_UART Control register and timer" */
+ r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT,
+ 0x9c | (ctrl << 8), a | 0x80);
+ } else {
+ r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x1312, a);
+ if (r)
+ return r;
+
+ r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x2518, ctrl);
+ if (r)
+ return r;
+ }
return r;
}
@@ -209,6 +227,14 @@ out: kfree(buffer);
/* -------------------------------------------------------------------------- */
+static int ch341_probe(struct usb_serial *serial,
+ const struct usb_device_id *id)
+{
+ usb_set_serial_data(serial, (void *)id->driver_info);
+
+ return 0;
+}
+
static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
{
const unsigned int size = 2;
@@ -229,11 +255,7 @@ static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
if (r < 0)
goto out;
- r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x2518, priv->lcr);
- if (r < 0)
- goto out;
-
- r = ch341_init_set_baudrate(dev, priv, priv->lcr);
+ r = ch341_set_baudrate_lcr(dev, priv, priv->lcr);
if (r < 0)
goto out;
@@ -259,6 +281,7 @@ static int ch341_port_probe(struct usb_serial_port *port)
* settings, so set a sane 8N1 default.
*/
priv->lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8;
+ priv->quirks = (unsigned long)usb_get_serial_data(port->serial);
r = ch341_configure(port->serial->dev, priv);
if (r < 0)
@@ -395,7 +418,7 @@ static void ch341_set_termios(struct tty_struct *tty,
if (baud_rate) {
priv->baud_rate = baud_rate;
- r = ch341_init_set_baudrate(port->serial->dev, priv, ctrl);
+ r = ch341_set_baudrate_lcr(port->serial->dev, priv, ctrl);
if (r < 0 && old_termios) {
priv->baud_rate = tty_termios_baud_rate(old_termios);
tty_termios_copy_hw(&tty->termios, old_termios);
@@ -628,6 +651,7 @@ static struct usb_serial_driver ch341_device = {
.tiocmset = ch341_tiocmset,
.tiocmiwait = usb_serial_generic_tiocmiwait,
.read_int_callback = ch341_read_int_callback,
+ .probe = ch341_probe,
.port_probe = ch341_port_probe,
.port_remove = ch341_port_remove,
.reset_resume = ch341_reset_resume,
--
2.10.2
--
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