linux-imx

power_supply: power_supply_read_temp only if use_cnt > 0

Change power_supply_read_temp() to use power_supply_get_property()
so that it will check the use_cnt and ensure it is > 0. The use_cnt
will be incremented at the end of __power_supply_register, so this
will block to case where get_property can be called before the supply
is fully registered. This fixes the issue show in the stack below:

[    1.452598] power_supply_read_temp+0x78/0x80
[    1.458680] thermal_zone_get_temp+0x5c/0x11c
[    1.464765] thermal_zone_device_update+0x34/0xb4
[    1.471195] thermal_zone_device_register+0x87c/0x8cc
[    1.477974] __power_supply_register+0x364/0x424
[    1.484317] power_supply_register_no_ws+0x10/0x18
[    1.490833] bq27xxx_battery_setup+0x10c/0x164
[    1.497003] bq27xxx_battery_i2c_probe+0xd0/0x1b0
[    1.503435] i2c_device_probe+0x174/0x240
[    1.509172] driver_probe_device+0x1fc/0x29c
[    1.515167] __driver_attach+0xa4/0xa8
[    1.520643] bus_for_each_dev+0x58/0x98
[    1.526204] driver_attach+0x20/0x28
[    1.531505] bus_add_driver+0x1c8/0x22c
[    1.537067] driver_register+0x68/0x108
[    1.542630] i2c_register_driver+0x38/0x7c
[    1.548457] bq27xxx_battery_i2c_driver_init+0x18/0x20
[    1.555321] do_one_initcall+0x38/0x12c
[    1.560886] kernel_init_freeable+0x148/0x1ec
[    1.566972] kernel_init+0x10/0xfc
[    1.572101] ret_from_fork+0x10/0x40

Also make the same change to ps_get_max_charge_cntl_limit() and
ps_get_cur_chrage_cntl_limit() to be safe. Lastly, change the return
value of power_supply_get_property() to -EAGAIN from -ENODEV if
use_cnt <= 0.

Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
Cc: stable@vger.kernel.org
Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>