USB: mos7840: remove smp barriers from icount handling

Remove SMP memory barriers from icount handling and rely on the barriers
implied by wait_event, sleep and locks, while using the port lock to
guarantee atomicity.

This is a step in moving over to the generic icount implementations.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index 979ef1999581271faa65026ef63702feacd21dcb..7af3d4206523eeb0937fe373dfd9fb9eace9add6 100644 (file)
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -406,22 +406,14 @@ static void mos7840_handle_new_msr(struct moschip_port *port, __u8 new_msr)
                icount = &mos7840_port->icount;
 
                /* update input line counters */
-               if (new_msr & MOS_MSR_DELTA_CTS) {
+               if (new_msr & MOS_MSR_DELTA_CTS)
                        icount->cts++;
-                       smp_wmb();
-               }
-               if (new_msr & MOS_MSR_DELTA_DSR) {
+               if (new_msr & MOS_MSR_DELTA_DSR)
                        icount->dsr++;
-                       smp_wmb();
-               }
-               if (new_msr & MOS_MSR_DELTA_CD) {
+               if (new_msr & MOS_MSR_DELTA_CD)
                        icount->dcd++;
-                       smp_wmb();
-               }
-               if (new_msr & MOS_MSR_DELTA_RI) {
+               if (new_msr & MOS_MSR_DELTA_RI)
                        icount->rng++;
-                       smp_wmb();
-               }
 
                mos7840_port->delta_msr_cond = 1;
                wake_up_interruptible(&port->port->delta_msr_wait);
@@ -443,22 +435,14 @@ static void mos7840_handle_new_lsr(struct moschip_port *port, __u8 new_lsr)
 
        /* update input line counters */
        icount = &port->icount;
-       if (new_lsr & SERIAL_LSR_BI) {
+       if (new_lsr & SERIAL_LSR_BI)
                icount->brk++;
-               smp_wmb();
-       }
-       if (new_lsr & SERIAL_LSR_OE) {
+       if (new_lsr & SERIAL_LSR_OE)
                icount->overrun++;
-               smp_wmb();
-       }
-       if (new_lsr & SERIAL_LSR_PE) {
+       if (new_lsr & SERIAL_LSR_PE)
                icount->parity++;
-               smp_wmb();
-       }
-       if (new_lsr & SERIAL_LSR_FE) {
+       if (new_lsr & SERIAL_LSR_FE)
                icount->frame++;
-               smp_wmb();
-       }
 }
 
 /************************************************************************/
@@ -778,7 +762,6 @@ static void mos7840_bulk_in_callback(struct urb *urb)
                tty_insert_flip_string(tport, data, urb->actual_length);
                tty_flip_buffer_push(tport);
                mos7840_port->icount.rx += urb->actual_length;
-               smp_wmb();
                dev_dbg(&port->dev, "mos7840_port->icount.rx is %d:\n", mos7840_port->icount.rx);
        }
 
@@ -1507,7 +1490,6 @@ static int mos7840_write(struct tty_struct *tty, struct usb_serial_port *port,
        }
        bytes_sent = transfer_size;
        mos7840_port->icount.tx += transfer_size;
-       smp_wmb();
        dev_dbg(&port->dev, "mos7840_port->icount.tx is %d:\n", mos7840_port->icount.tx);
 exit:
        return bytes_sent;
@@ -2133,11 +2115,14 @@ static int mos7840_get_icount(struct tty_struct *tty,
        struct usb_serial_port *port = tty->driver_data;
        struct moschip_port *mos7840_port;
        struct async_icount cnow;
+       unsigned long flags;
 
        mos7840_port = mos7840_get_port_private(port);
+
+       spin_lock_irqsave(&port->lock, flags);
        cnow = mos7840_port->icount;
+       spin_unlock_irqrestore(&port->lock, flags);
 
-       smp_rmb();
        icount->cts = cnow.cts;
        icount->dsr = cnow.dsr;
        icount->rng = cnow.rng;
@@ -2166,7 +2151,7 @@ static int mos7840_ioctl(struct tty_struct *tty,
        struct usb_serial_port *port = tty->driver_data;
        void __user *argp = (void __user *)arg;
        struct moschip_port *mos7840_port;
-
+       unsigned long flags;
        struct async_icount cnow;
        struct async_icount cprev;
 
@@ -2197,7 +2182,9 @@ static int mos7840_ioctl(struct tty_struct *tty,
 
        case TIOCMIWAIT:
                dev_dbg(&port->dev, "%s  TIOCMIWAIT\n", __func__);
+               spin_lock_irqsave(&port->lock, flags);
                cprev = mos7840_port->icount;
+               spin_unlock_irqrestore(&port->lock, flags);
                while (1) {
                        /* interruptible_sleep_on(&mos7840_port->delta_msr_wait); */
                        mos7840_port->delta_msr_cond = 0;
@@ -2213,11 +2200,14 @@ static int mos7840_ioctl(struct tty_struct *tty,
                        if (port->serial->disconnected)
                                return -EIO;
 
+                       spin_lock_irqsave(&port->lock, flags);
                        cnow = mos7840_port->icount;
-                       smp_rmb();
+                       spin_unlock_irqrestore(&port->lock, flags);
+
                        if (cnow.rng == cprev.rng && cnow.dsr == cprev.dsr &&
                            cnow.dcd == cprev.dcd && cnow.cts == cprev.cts)
                                return -EIO;    /* no change => error */
+
                        if (((arg & TIOCM_RNG) && (cnow.rng != cprev.rng)) ||
                            ((arg & TIOCM_DSR) && (cnow.dsr != cprev.dsr)) ||
                            ((arg & TIOCM_CD) && (cnow.dcd != cprev.dcd)) ||