wimax/i2400m: clarify and fix i2400m->{ready,updown}

The i2400m driver uses two different bits to distinguish how much the
driver is up. i2400m->ready is used to denote that the infrastructure
to communicate with the device is up and running. i2400m->updown is
used to indicate if 'ready' and the device is up and running, ready to
take control and data traffic.

However, all this was pretty dirty and not clear, with many open spots
where race conditions were present.

This commit cleans up the situation by:

 - documenting the usage of both bits

 - setting them only in specific, well controlled places
   (i2400m_dev_start, i2400m_dev_stop)

 - ensuring the i2400m workqueue can't get in the middle of the
   setting by flushing it when i2400m->ready is set to zero. This
   allows the report hook not having to check again for the bit to be
   set [rx.c:i2400m_report_hook_work()].

 - using i2400m->updown to determine if the device is up and running
   instead of the wimax state in i2400m_dev_reset_handle().

 - not loosing missed messages sent by the hardware before
   i2400m->ready is set. In rx.c, whatever the device sends can be
   sent to user space over the message pipes as soon as the wimax
   device is registered, so don't wait for i2400m->ready to be set.

Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/net/wimax/i2400m/usb.c b/drivers/net/wimax/i2400m/usb.c
index 07653ded6c59..f4dfb60bb628 100644
--- a/drivers/net/wimax/i2400m/usb.c
+++ b/drivers/net/wimax/i2400m/usb.c
@@ -516,7 +516,10 @@ void i2400mu_disconnect(struct usb_interface *iface)
  * So at the end, the three cases require common handling.
  *
  * If at the time of this call the device's firmware is not loaded,
- * nothing has to be done.
+ * nothing has to be done. Note we can be "loose" about not reading
+ * i2400m->updown under i2400m->init_mutex. If it happens to change
+ * inmediately, other parts of the call flow will fail and effectively
+ * catch it.
  *
  * If the firmware is loaded, we need to:
  *
@@ -555,6 +558,7 @@ int i2400mu_suspend(struct usb_interface *iface, pm_message_t pm_msg)
 #endif
 
 	d_fnstart(3, dev, "(iface %p pm_msg %u)\n", iface, pm_msg.event);
+	rmb();		/* see i2400m->updown's documentation  */
 	if (i2400m->updown == 0)
 		goto no_firmware;
 	if (i2400m->state == I2400M_SS_DATA_PATH_CONNECTED && is_autosuspend) {
@@ -608,6 +612,7 @@ int i2400mu_resume(struct usb_interface *iface)
 	struct i2400m *i2400m = &i2400mu->i2400m;
 
 	d_fnstart(3, dev, "(iface %p)\n", iface);
+	rmb();		/* see i2400m->updown's documentation  */
 	if (i2400m->updown == 0) {
 		d_printf(1, dev, "fw was down, no resume neeed\n");
 		goto out;