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>

1 files changed, 19 insertions, 29 deletions

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index 979ef1999581..7af3d4206523 100644
--- 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)) ||