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USB: serial: cp210x: suppress modem-control errors 

The CP210X_SET_MHS request cannot be used to control RTS when hardware
flow control (auto-RTS) is enabled and instead returns an error which is
currently logged as:

	cp210x ttyUSB0: failed set request 0x7 status: -32

when opening and closing a port (and on TIOCMSET requests).

Add a crtscts flag to keep track of the hardware flow-control setting
and use it to suppress any request to change RTS when auto-RTS is
enabled.

Note that RTS is still deasserted when disabling the UART as part of
close.

Reported-by: Pho Tran <pho.tran@silabs.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
This commit is contained in:
Johan Hovold 2021-01-25 14:48:11 +01:00
parent fea7372cbc
commit 5951b85088
1 changed files with 30 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
drivers/usb/serial/cp210x.c
View File

@ -21,6 +21,7 @@
#include <linux/usb/serial.h>
#include <linux/gpio/driver.h>
#include <linux/bitops.h>
#include <linux/mutex.h>
#define DRIVER_DESC "Silicon Labs CP210x RS232 serial adaptor driver"
@ -264,7 +265,10 @@ struct cp210x_port_private {
u8 bInterfaceNumber;
bool event_mode;
enum cp210x_event_state event_state;
u8 lsr;
u8 lsr;
struct mutex mutex;
bool crtscts;
};
static struct usb_serial_driver cp210x_device = {
@ -1117,6 +1121,7 @@ static bool cp210x_termios_change(const struct ktermios *a, const struct ktermio
static void cp210x_set_flow_control(struct tty_struct *tty,
struct usb_serial_port *port, struct ktermios *old_termios)
{
struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
struct cp210x_special_chars chars;
struct cp210x_flow_ctl flow_ctl;
u32 flow_repl;
@ -1143,10 +1148,12 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
return;
}
mutex_lock(&port_priv->mutex);
ret = cp210x_read_reg_block(port, CP210X_GET_FLOW, &flow_ctl,
sizeof(flow_ctl));
if (ret)
return;
goto out_unlock;
ctl_hs = le32_to_cpu(flow_ctl.ulControlHandshake);
flow_repl = le32_to_cpu(flow_ctl.ulFlowReplace);
@ -1161,10 +1168,12 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
ctl_hs |= CP210X_SERIAL_CTS_HANDSHAKE;
flow_repl &= ~CP210X_SERIAL_RTS_MASK;
flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_FLOW_CTL);
port_priv->crtscts = true;
} else {
ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
flow_repl &= ~CP210X_SERIAL_RTS_MASK;
flow_repl |= CP210X_SERIAL_RTS_SHIFT(CP210X_SERIAL_RTS_ACTIVE);
port_priv->crtscts = false;
}
if (I_IXOFF(tty))
@ -1188,6 +1197,8 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,
sizeof(flow_ctl));
out_unlock:
mutex_unlock(&port_priv->mutex);
}
static void cp210x_set_termios(struct tty_struct *tty,
@ -1272,7 +1283,9 @@ static int cp210x_tiocmset(struct tty_struct *tty,
static int cp210x_tiocmset_port(struct usb_serial_port *port,
unsigned int set, unsigned int clear)
{
struct cp210x_port_private *port_priv = usb_get_serial_port_data(port);
u16 control = 0;
int ret;
if (set & TIOCM_RTS) {
control |= CONTROL_RTS;
@ -1291,9 +1304,22 @@ static int cp210x_tiocmset_port(struct usb_serial_port *port,
control |= CONTROL_WRITE_DTR;
}
mutex_lock(&port_priv->mutex);
/*
* SET_MHS cannot be used to control RTS when auto-RTS is enabled.
* Note that RTS is still deasserted when disabling the UART on close.
*/
if (port_priv->crtscts)
control &= ~CONTROL_WRITE_RTS;
dev_dbg(&port->dev, "%s - control = 0x%.4x\n", __func__, control);
return cp210x_write_u16_reg(port, CP210X_SET_MHS, control);
ret = cp210x_write_u16_reg(port, CP210X_SET_MHS, control);
mutex_unlock(&port_priv->mutex);
return ret;
}
static void cp210x_dtr_rts(struct usb_serial_port *port, int on)
@ -1770,6 +1796,7 @@ static int cp210x_port_probe(struct usb_serial_port *port)
return -ENOMEM;
port_priv->bInterfaceNumber = cp210x_interface_num(serial);
mutex_init(&port_priv->mutex);
usb_set_serial_port_data(port, port_priv);