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path: root/drivers/usb/serial/ch341.c
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Diffstat (limited to 'drivers/usb/serial/ch341.c')
-rw-r--r--drivers/usb/serial/ch341.c68
1 files changed, 65 insertions, 3 deletions
diff --git a/drivers/usb/serial/ch341.c b/drivers/usb/serial/ch341.c
index c5ecdcd51ffc..89675ee29645 100644
--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -73,6 +73,8 @@
#define CH341_LCR_CS6 0x01
#define CH341_LCR_CS5 0x00
+#define CH341_QUIRK_LIMITED_PRESCALER BIT(0)
+
static const struct usb_device_id id_table[] = {
{ USB_DEVICE(0x4348, 0x5523) },
{ USB_DEVICE(0x1a86, 0x7523) },
@@ -87,6 +89,7 @@ struct ch341_private {
u8 mcr;
u8 msr;
u8 lcr;
+ unsigned long quirks;
};
static void ch341_set_termios(struct tty_struct *tty,
@@ -159,9 +162,11 @@ static const speed_t ch341_min_rates[] = {
* 2 <= div <= 256 if fact = 0, or
* 9 <= div <= 256 if fact = 1
*/
-static int ch341_get_divisor(speed_t speed)
+static int ch341_get_divisor(struct ch341_private *priv)
{
unsigned int fact, div, clk_div;
+ speed_t speed = priv->baud_rate;
+ bool force_fact0 = false;
int ps;
/*
@@ -187,8 +192,12 @@ static int ch341_get_divisor(speed_t speed)
clk_div = CH341_CLK_DIV(ps, fact);
div = CH341_CLKRATE / (clk_div * speed);
+ /* Some devices require a lower base clock if ps < 3. */
+ if (ps < 3 && (priv->quirks & CH341_QUIRK_LIMITED_PRESCALER))
+ force_fact0 = true;
+
/* Halve base clock (fact = 0) if required. */
- if (div < 9 || div > 255) {
+ if (div < 9 || div > 255 || force_fact0) {
div /= 2;
clk_div *= 2;
fact = 0;
@@ -227,7 +236,7 @@ static int ch341_set_baudrate_lcr(struct usb_device *dev,
if (!priv->baud_rate)
return -EINVAL;
- val = ch341_get_divisor(priv->baud_rate);
+ val = ch341_get_divisor(priv);
if (val < 0)
return -EINVAL;
@@ -308,6 +317,54 @@ out: kfree(buffer);
return r;
}
+static int ch341_detect_quirks(struct usb_serial_port *port)
+{
+ struct ch341_private *priv = usb_get_serial_port_data(port);
+ struct usb_device *udev = port->serial->dev;
+ const unsigned int size = 2;
+ unsigned long quirks = 0;
+ char *buffer;
+ int r;
+
+ buffer = kmalloc(size, GFP_KERNEL);
+ if (!buffer)
+ return -ENOMEM;
+
+ /*
+ * A subset of CH34x devices does not support all features. The
+ * prescaler is limited and there is no support for sending a RS232
+ * break condition. A read failure when trying to set up the latter is
+ * used to detect these devices.
+ */
+ r = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0), CH341_REQ_READ_REG,
+ USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
+ CH341_REG_BREAK, 0, buffer, size, DEFAULT_TIMEOUT);
+ if (r == -EPIPE) {
+ dev_dbg(&port->dev, "break control not supported\n");
+ quirks = CH341_QUIRK_LIMITED_PRESCALER;
+ r = 0;
+ goto out;
+ }
+
+ if (r != size) {
+ if (r >= 0)
+ r = -EIO;
+ dev_err(&port->dev, "failed to read break control: %d\n", r);
+ goto out;
+ }
+
+ r = 0;
+out:
+ kfree(buffer);
+
+ if (quirks) {
+ dev_dbg(&port->dev, "enabling quirk flags: 0x%02lx\n", quirks);
+ priv->quirks |= quirks;
+ }
+
+ return r;
+}
+
static int ch341_port_probe(struct usb_serial_port *port)
{
struct ch341_private *priv;
@@ -330,6 +387,11 @@ static int ch341_port_probe(struct usb_serial_port *port)
goto error;
usb_set_serial_port_data(port, priv);
+
+ r = ch341_detect_quirks(port);
+ if (r < 0)
+ goto error;
+
return 0;
error: kfree(priv);