power: charger-manager: Fix accessing invalidated power supply after fuel gauge unbind

power: charger-manager: Fix accessing invalidated power supply after fuel gauge unbind

The charger manager obtained reference to fuel gauge power supply in probe
with power_supply_get_by_name() for later usage. However if fuel gauge
driver was removed and re-added then this reference would point to old
power supply (from driver which was removed).

This lead to accessing old (and probably invalid) memory which could be
observed with:
$ echo "12-0036" > /sys/bus/i2c/drivers/max17042/unbind
$ echo "12-0036" > /sys/bus/i2c/drivers/max17042/bind
$ cat /sys/devices/virtual/power_supply/battery/capacity
[  240.480084] INFO: task cat:1393 blocked for more than 120 seconds.
[  240.484799]       Not tainted 3.17.0-next-20141007-00028-ge60b6dd79570 #203
[  240.491782] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  240.499589] cat             D c0469530     0  1393      1 0x00000000
[  240.505947] [<c0469530>] (__schedule) from [<c0469d3c>] (schedule_preempt_disabled+0x14/0x20)
[  240.514449] [<c0469d3c>] (schedule_preempt_disabled) from [<c046af08>] (mutex_lock_nested+0x1bc/0x458)
[  240.523736] [<c046af08>] (mutex_lock_nested) from [<c0287a98>] (regmap_read+0x30/0x60)
[  240.531647] [<c0287a98>] (regmap_read) from [<c032238c>] (max17042_get_property+0x2e8/0x350)
[  240.540055] [<c032238c>] (max17042_get_property) from [<c03247d8>] (charger_get_property+0x264/0x348)
[  240.549252] [<c03247d8>] (charger_get_property) from [<c0320764>] (power_supply_show_property+0x48/0x1e0)
[  240.558808] [<c0320764>] (power_supply_show_property) from [<c027308c>] (dev_attr_show+0x1c/0x48)
[  240.567664] [<c027308c>] (dev_attr_show) from [<c0141fb0>] (sysfs_kf_seq_show+0x84/0x104)
[  240.575814] [<c0141fb0>] (sysfs_kf_seq_show) from [<c0140b18>] (kernfs_seq_show+0x24/0x28)
[  240.584061] [<c0140b18>] (kernfs_seq_show) from [<c0104574>] (seq_read+0x1b0/0x484)
[  240.591702] [<c0104574>] (seq_read) from [<c00e1e24>] (vfs_read+0x88/0x144)
[  240.598640] [<c00e1e24>] (vfs_read) from [<c00e1f20>] (SyS_read+0x40/0x8c)
[  240.605507] [<c00e1f20>] (SyS_read) from [<c000e760>] (ret_fast_syscall+0x0/0x48)
[  240.612952] 4 locks held by cat/1393:
[  240.616589]  #0:  (&p->lock){+.+.+.}, at: [<c01043f4>] seq_read+0x30/0x484
[  240.623414]  #1:  (&of->mutex){+.+.+.}, at: [<c01417dc>] kernfs_seq_start+0x1c/0x8c
[  240.631086]  #2:  (s_active#31){++++.+}, at: [<c01417e4>] kernfs_seq_start+0x24/0x8c
[  240.638777]  #3:  (&map->mutex){+.+...}, at: [<c0287a98>] regmap_read+0x30/0x60

The charger-manager should get reference to fuel gauge power supply on
each use of get_property callback. The thermal zone 'tzd' field of
power supply should not be used because of the same reason.

Additionally this change solves also the issue with nested
thermal_zone_get_temp() calls and related false lockdep positive for
deadlock for thermal zone's mutex [1]. When fuel gauge is used as source of
temperature then the charger manager forwards its get_temp calls to fuel
gauge thermal zone. So actually different mutexes are used (one for
charger manager thermal zone and second for fuel gauge thermal zone) but
for lockdep this is one class of mutex.

The recursion is removed by retrieving temperature through power
supply's get_property().

In case external thermal zone is used ('cm-thermal-zone' property is
present in DTS) the recursion does not exist. Charger manager simply
exports POWER_SUPPLY_PROP_TEMP_AMBIENT property (instead of
POWER_SUPPLY_PROP_TEMP) thus no thermal zone is created for this power
supply.

[1] https://lkml.org/lkml/2014/10/6/309

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: <stable@vger.kernel.org>
Fixes: 3bb3dbbd56ea ("power_supply: Add initial Charger-Manager driver")
Signed-off-by: Sebastian Reichel <sre@kernel.org>