From: Peter Hung <hpeter@gmail.com>
To: johan@kernel.org
Cc: gregkh@linuxfoundation.org, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org, tom_tsai@fintek.com.tw,
peter_hong@fintek.com.tw,
Peter Hung <hpeter+linux_kernel@gmail.com>
Subject: [PATCH V6 08/10] USB: f81232: fix read MSR strange value
Date: Mon, 16 Feb 2015 15:58:00 +0800 [thread overview]
Message-ID: <1424073482-18164-9-git-send-email-hpeter+linux_kernel@gmail.com> (raw)
In-Reply-To: <1424073482-18164-1-git-send-email-hpeter+linux_kernel@gmail.com>
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 fasterly.
So we add more check not only UART_MSR_ANY_DELTA but also with
comparing DCD/RI/DSR/CTS change with old value. Due to 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@gmail.com>
---
drivers/usb/serial/f81232.c | 23 +++++++++++++++++------
1 file changed, 17 insertions(+), 6 deletions(-)
diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
index c87a3eb..94c05d7 100644
--- a/drivers/usb/serial/f81232.c
+++ b/drivers/usb/serial/f81232.c
@@ -110,7 +110,8 @@ static void f81232_read_msr(struct usb_serial_port *port)
{
int status;
unsigned long flags;
- u8 current_msr;
+ u8 current_msr, prev_msr;
+ u8 msr_mask = ~UART_MSR_ANY_DELTA;
struct tty_struct *tty;
struct f81232_private *priv = usb_get_serial_port_data(port);
@@ -123,7 +124,21 @@ static void f81232_read_msr(struct usb_serial_port *port)
return;
}
- if (!(current_msr & UART_MSR_ANY_DELTA))
+ /*
+ * The 7~4 bits of MSR will change but the 3~0 bits of MSR(delta)
+ * maybe not change when set & get MCR fasterly.
+ *
+ * So we add more check with comparing DCD/RI/DSR/CTS
+ * change. and direct save msr when read.
+ */
+
+ spin_lock_irqsave(&priv->lock, flags);
+ prev_msr = priv->modem_status;
+ priv->modem_status = current_msr;
+ spin_unlock_irqrestore(&priv->lock, flags);
+
+ if (!(current_msr & UART_MSR_ANY_DELTA) &&
+ !((prev_msr ^ current_msr) & msr_mask))
return;
tty = tty_port_tty_get(&port->port);
@@ -136,10 +151,6 @@ static void f81232_read_msr(struct usb_serial_port *port)
tty_kref_put(tty);
}
- spin_lock_irqsave(&priv->lock, flags);
- priv->modem_status = current_msr;
- spin_unlock_irqrestore(&priv->lock, flags);
-
wake_up_interruptible(&port->port.delta_msr_wait);
}
--
1.9.1
next prev parent reply other threads:[~2015-02-16 7:58 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-16 7:57 [PATCH V6 00/10] USB: f81232: V6 patches Peter Hung
2015-02-16 7:57 ` [PATCH V6 01/10] USB: f81232: rename private struct member name Peter Hung
2015-02-16 7:57 ` [PATCH V6 02/10] USB: f81232: implement read IIR/MSR with endpoint Peter Hung
2015-02-17 8:30 ` Johan Hovold
2015-02-16 7:57 ` [PATCH V6 03/10] USB: f81232: implement RX bulk-in ep Peter Hung
2015-02-16 19:41 ` Greg KH
2015-02-17 1:41 ` Peter Hung
2015-02-17 10:06 ` David Laight
2015-02-17 14:48 ` 'Greg KH'
2015-02-16 7:57 ` [PATCH V6 04/10] USB: f81232: implement set_termios Peter Hung
2015-02-17 8:59 ` Johan Hovold
2015-02-16 7:57 ` [PATCH V6 05/10] USB: f81232: implement MCR/MSR function Peter Hung
2015-02-17 9:40 ` Johan Hovold
2015-02-16 7:57 ` [PATCH V6 06/10] USB: f81232: clarify f81232_ioctl and fix Peter Hung
2015-02-16 7:57 ` [PATCH V6 07/10] USB: f81232: fix error in f81232_carrier_raised() Peter Hung
2015-02-17 9:44 ` Johan Hovold
2015-02-16 7:58 ` Peter Hung [this message]
2015-02-17 9:51 ` [PATCH V6 08/10] USB: f81232: fix read MSR strange value Johan Hovold
2015-02-24 2:17 ` Peter Hung
2015-02-16 7:58 ` [PATCH V6 09/10] USB: f81232: implement delta change for MSR count Peter Hung
2015-02-16 7:58 ` [PATCH V6 10/10] USB: f81232: modify/add author Peter Hung
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