[PATCH V7 05/11] USB: f81232: implement read IIR/MSR with endpoint

[Peter Hung]

The interrupt endpoint will report current IIR. If we got IIR with MSR changed
, We will do read MSR with interrupt_work worker to do f81232_read_msr()
function.

We also confirmd MSR strange delta value is not locking-issue. The issue
is set MCR & get MSR before IIR notice with MSR changed (Loopback only).

When we use RS232 loopback, assume doing RTS change will cause
CTS change, DTR change will cause DCD/DSR change too.

Sometimes we got 7~4 bits of MSR changed but the 3~0 bits of
MSR(delta) maybe not changed when set & get MCR rapidly.

So we add more check not only UART_MSR_ANY_DELTA but also with
comparing DCD/RI/DSR/CTS change with old value. Because of the state
bit is always correct, we direct save msr when read.

The following step to reproduce this problem with while loop step 1~4:
1. ioctl(fd, TIOCMSET, &data) to set RTS or DTR
2. ioctl(fd, TIOCMGET, &data) to read CTS or DCD/DSR state
3. ioctl(fd, TIOCMSET, &data) to unset RTS or DTR
4. ioctl(fd, TIOCMGET, &data) to read CTS or DCD/DSR state

Signed-off-by: Peter Hung <hpeter+linux_kernel@xxxxxxxxx>
---
 drivers/usb/serial/f81232.c | 106 ++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 98 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
index bf072fe..339be30 100644
--- a/drivers/usb/serial/f81232.c
+++ b/drivers/usb/serial/f81232.c
@@ -36,6 +36,9 @@ MODULE_DEVICE_TABLE(usb, id_table);
 #define F81232_GET_REGISTER	0xc0
 #define F81232_SET_REGISTER	0x40
 
+#define SERIAL_BASE_ADDRESS	0x0120
+#define MODEM_STATUS_REGISTER	(0x06 + SERIAL_BASE_ADDRESS)
+
 #define CONTROL_DTR			0x01
 #define CONTROL_RTS			0x02
 
@@ -54,6 +57,8 @@ struct f81232_private {
 	struct mutex lock;
 	u8 line_control;
 	u8 modem_status;
+	struct work_struct interrupt_work;
+	struct usb_serial_port *port;
 };
 
 static int f81232_get_register(struct usb_serial_port *port, u16 reg, u8 *data)
@@ -130,17 +135,92 @@ static int f81232_set_register(struct usb_serial_port *port, u16 reg, u8 data)
 	kfree(tmp);
 	return status;
 }
+
+static void f81232_read_msr(struct usb_serial_port *port)
+{
+	int status;
+	u8 current_msr, prev_msr;
+	u8 msr_mask = ~UART_MSR_ANY_DELTA;
+	u8 msr_changed_bit;
+	struct tty_struct *tty;
+	struct f81232_private *priv = usb_get_serial_port_data(port);
+
+	status = f81232_get_register(port, MODEM_STATUS_REGISTER,
+			&current_msr);
+	if (status) {
+		dev_err(&port->dev, "%s fail, status: %d\n", __func__, status);
+		return;
+	}
+
+	/*
+	*  The 7~4 bits of MSR will change but the 3~0 bits of MSR(delta)
+	*  maybe not change when set MCR & get MSR rapidly.
+	*
+	*  So we add more check with comparing DCD/RI/DSR/CTS
+	*  change. and direct save msr when read.
+	*/
+
+	mutex_lock(&priv->lock);
+	prev_msr = priv->modem_status;
+	priv->modem_status = current_msr;
+	mutex_unlock(&priv->lock);
+
+	if (!(current_msr & UART_MSR_ANY_DELTA) &&
+		!((prev_msr ^ current_msr) & msr_mask))
+		return;
+
+	/* find checked delta bits set */
+	msr_changed_bit =
+		(current_msr & UART_MSR_ANY_DELTA) << 4;
+
+	/* append with not delta but changed bits */
+	msr_changed_bit |= (prev_msr ^ current_msr) & msr_mask;
+
+	if (msr_changed_bit & UART_MSR_CTS)
+		port->icount.cts++;
+	if (msr_changed_bit & UART_MSR_DSR)
+		port->icount.dsr++;
+	if (msr_changed_bit & UART_MSR_RI)
+		port->icount.rng++;
+	if (msr_changed_bit & UART_MSR_DCD) {
+
+		port->icount.dcd++;
+		tty = tty_port_tty_get(&port->port);
+		if (tty) {
+
+			usb_serial_handle_dcd_change(port, tty,
+					current_msr & UART_MSR_DCD);
+
+			tty_kref_put(tty);
+		}
+	}
+
+	wake_up_interruptible(&port->port.delta_msr_wait);
+}
+
 static void f81232_update_line_status(struct usb_serial_port *port,
 				      unsigned char *data,
-				      unsigned int actual_length)
+				      size_t actual_length)
 {
-	/*
-	 * FIXME: Update port->icount, and call
-	 *
-	 *		wake_up_interruptible(&port->port.delta_msr_wait);
-	 *
-	 *	  on MSR changes.
-	 */
+	struct f81232_private *priv = usb_get_serial_port_data(port);
+
+	if (!actual_length)
+		return;
+
+	switch (data[0] & 0x07) {
+	case 0x00: /* msr change */
+		dev_dbg(&port->dev, "IIR: MSR Change: %02x\n", data[0]);
+		schedule_work(&priv->interrupt_work);
+		break;
+	case 0x02: /* tx-empty */
+		break;
+	case 0x04: /* rx data available */
+		break;
+	case 0x06: /* lsr change */
+		/* we can forget it. the LSR will read from bulk-in */
+		dev_dbg(&port->dev, "IIR: LSR Change: %02x\n", data[0]);
+		break;
+	}
 }
 
 static void f81232_read_int_callback(struct urb *urb)
@@ -351,6 +431,14 @@ static int f81232_ioctl(struct tty_struct *tty,
 	return -ENOIOCTLCMD;
 }
 
+static void  f81232_interrupt_work(struct work_struct *work)
+{
+	struct f81232_private *priv =
+		container_of(work, struct f81232_private, interrupt_work);
+
+	f81232_read_msr(priv->port);
+}
+
 static int f81232_port_probe(struct usb_serial_port *port)
 {
 	struct f81232_private *priv;
@@ -360,10 +448,12 @@ static int f81232_port_probe(struct usb_serial_port *port)
 		return -ENOMEM;
 
 	mutex_init(&priv->lock);
+	INIT_WORK(&priv->interrupt_work,  f81232_interrupt_work);
 
 	usb_set_serial_port_data(port, priv);
 
 	port->port.drain_delay = 256;
+	priv->port = port;
 
 	return 0;
 }
-- 
1.9.1

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