wimax/i2400m: fix for missed reset events if triggered by dev_reset_handle()

The problem is only seen on SDIO interface since on USB, a bus reset would
really re-probe the driver, but on SDIO interface, a bus reset will not
re-enumerate the SDIO bus, so no driver re-probe is happening. Therefore,
on SDIO interface, the reset event should be still detected and handled by
dev_reset_handle().

Problem description:
Whenever a reboot barker is received during operational mode (i2400m->boot_mode == 0),
dev_reset_handle() is invoked to handle that function reset event.
dev_reset_handle() then sets the flag i2400m->boot_mode to 1 indicating the device is
back to bootmode before proceeding to dev_stop() and dev_start().
If dev_start() returns failure, a bus reset is triggered by dev_reset_handle().

The flag i2400m->boot_mode then remains 1 when the second reboot barker arrives.
However the interrupt service routine i2400ms_rx() instead of invoking dev_reset_handle()
to handle that reset event, it filters out that boot event to bootmode because it sees
the flag i2400m->boot_mode equal to 1.

The fix:
Maintain the flag i2400m->boot_mode within dev_reset_handle() and set the flag
i2400m->boot_mode to 1 when entering dev_reset_handle(). It remains 1
until the dev_reset_handle() issues a bus reset. ie: the bus reset is
taking place just like it happens for the first time during operational mode.

To denote the actual device state and the state we expect, a flag i2400m->alive
is introduced in addition to the existing flag i2400m->updown.
It's maintained with the same way for i2400m->updown but instead of reflecting
the actual state like i2400m->updown does, i2400m->alive maintains the state
we expect. i2400m->alive is set 1 just like whenever i2400m->updown is set 1.
Yet i2400m->alive remains 1 since we expect the device to be up all the time
until the driver is removed. See the doc for @alive in i2400m.h.

An enumeration I2400M_BUS_RESET_RETRIES is added to define the maximum number of
bus resets that a device reboot can retry.

A counter i2400m->bus_reset_retries is added to track how many bus resets
have been retried in one device reboot. If I2400M_BUS_RESET_RETRIES bus resets
were retried in this boot, we give up any further retrying so the device would enter
low power state. The counter i2400m->bus_reset_retries is incremented whenever
dev_reset_handle() is issuing a bus reset and is cleared to 0 when dev_start() is
successfully done, ie: a successful reboot.

Signed-off-by: Cindy H Kao <cindy.h.kao@intel.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/net/wimax/i2400m/i2400m.h b/drivers/net/wimax/i2400m/i2400m.h
index da218b9..ad8e6a3 100644
--- a/drivers/net/wimax/i2400m/i2400m.h
+++ b/drivers/net/wimax/i2400m/i2400m.h
@@ -177,6 +177,11 @@ enum {
 	I2400M_BM_ACK_BUF_SIZE = 256,
 };
 
+enum {
+	/* Maximum number of bus reset can be retried */
+	I2400M_BUS_RESET_RETRIES = 3,
+};
+
 /**
  * struct i2400m_poke_table - Hardware poke table for the Intel 2400m
  *
@@ -517,6 +522,29 @@ struct i2400m_barker_db;
  *     same.
  *
  * @pm_notifier: used to register for PM events
+ *
+ * @bus_reset_retries: counter for the number of bus resets attempted for
+ *	this boot. It's not for tracking the number of bus resets during
+ *	the whole driver life cycle (from insmod to rmmod) but for the
+ *	number of dev_start() executed until dev_start() returns a success
+ *	(ie: a good boot means a dev_stop() followed by a successful
+ *	dev_start()). dev_reset_handler() increments this counter whenever
+ *	it is triggering a bus reset. It checks this counter to decide if a
+ *	subsequent bus reset should be retried. dev_reset_handler() retries
+ *	the bus reset until dev_start() succeeds or the counter reaches
+ *	I2400M_BUS_RESET_RETRIES. The counter is cleared to 0 in
+ *	dev_reset_handle() when dev_start() returns a success,
+ *	ie: a successul boot is completed.
+ *
+ * @alive: flag to denote if the device *should* be alive. This flag is
+ *	everything like @updown (see doc for @updown) except reflecting
+ *	the device state *we expect* rather than the actual state as denoted
+ *	by @updown. It is set 1 whenever @updown is set 1 in dev_start().
+ *	Then the device is expected to be alive all the time
+ *	(i2400m->alive remains 1) until the driver is removed. Therefore
+ *	all the device reboot events detected can be still handled properly
+ *	by either dev_reset_handle() or .pre_reset/.post_reset as long as
+ *	the driver presents. It is set 0 along with @updown in dev_stop().
  */
 struct i2400m {
 	struct wimax_dev wimax_dev;	/* FIRST! See doc */
@@ -591,6 +619,12 @@ struct i2400m {
 	struct i2400m_barker_db *barker;
 
 	struct notifier_block pm_notifier;
+
+	/* counting bus reset retries in this boot */
+	atomic_t bus_reset_retries;
+
+	/* if the device is expected to be alive */
+	unsigned alive;
 };