• Viresh Kumar's avatar
    mfd: wm8994-core: Don't use managed regulator bulk get API · 1a41741f
    Viresh Kumar authored
    The kernel WARNs and then crashes today if wm8994_device_init() fails
    after calling devm_regulator_bulk_get().
    
    That happens because there are multiple devices involved here and the
    order in which managed resources are freed isn't correct.
    
    The regulators are added as children of wm8994->dev.  Whereas,
    devm_regulator_bulk_get() receives wm8994->dev as the device, though it
    gets the same regulators which were added as children of wm8994->dev
    earlier.
    
    During failures, the children are removed first and the core eventually
    calls regulator_unregister() for them. As regulator_put() was never done
    for them (opposite of devm_regulator_bulk_get()), the kernel WARNs at
    
    	WARN_ON(rdev->open_count);
    
    And eventually it crashes from debugfs_remove_recursive().
    
    --------x------------------x----------------
    
     wm8994 3-001a: Device is not a WM8994, ID is 0
     ------------[ cut here ]------------
     WARNING: CPU: 0 PID: 1 at /mnt/ssd/all/work/repos/devel/linux/drivers/regulator/core.c:4072 regulator_unregister+0xc8/0xd0
     Modules linked in:
     CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.0-rc6-00154-g54fe84cbd50b #41
     Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
     [<c010e24c>] (unwind_backtrace) from [<c010af38>] (show_stack+0x10/0x14)
     [<c010af38>] (show_stack) from [<c032a1c4>] (dump_stack+0x88/0x9c)
     [<c032a1c4>] (dump_stack) from [<c011a98c>] (__warn+0xe8/0x100)
     [<c011a98c>] (__warn) from [<c011aa54>] (warn_slowpath_null+0x20/0x28)
     [<c011aa54>] (warn_slowpath_null) from [<c0384a0c>] (regulator_unregister+0xc8/0xd0)
     [<c0384a0c>] (regulator_unregister) from [<c0406434>] (release_nodes+0x16c/0x1dc)
     [<c0406434>] (release_nodes) from [<c04039c4>] (__device_release_driver+0x8c/0x110)
     [<c04039c4>] (__device_release_driver) from [<c0403a64>] (device_release_driver+0x1c/0x28)
     [<c0403a64>] (device_release_driver) from [<c0402b24>] (bus_remove_device+0xd8/0x104)
     [<c0402b24>] (bus_remove_device) from [<c03ffcd8>] (device_del+0x10c/0x218)
     [<c03ffcd8>] (device_del) from [<c0404e4c>] (platform_device_del+0x1c/0x88)
     [<c0404e4c>] (platform_device_del) from [<c0404ec4>] (platform_device_unregister+0xc/0x20)
     [<c0404ec4>] (platform_device_unregister) from [<c0428bc0>] (mfd_remove_devices_fn+0x5c/0x64)
     [<c0428bc0>] (mfd_remove_devices_fn) from [<c03ff9d8>] (device_for_each_child_reverse+0x4c/0x78)
     [<c03ff9d8>] (device_for_each_child_reverse) from [<c04288c4>] (mfd_remove_devices+0x20/0x30)
     [<c04288c4>] (mfd_remove_devices) from [<c042758c>] (wm8994_device_init+0x2ac/0x7f0)
     [<c042758c>] (wm8994_device_init) from [<c04f14a8>] (i2c_device_probe+0x178/0x1fc)
     [<c04f14a8>] (i2c_device_probe) from [<c04036fc>] (driver_probe_device+0x214/0x2c0)
     [<c04036fc>] (driver_probe_device) from [<c0403854>] (__driver_attach+0xac/0xb0)
     [<c0403854>] (__driver_attach) from [<c0401a74>] (bus_for_each_dev+0x68/0x9c)
     [<c0401a74>] (bus_for_each_dev) from [<c0402cf0>] (bus_add_driver+0x1a0/0x218)
     [<c0402cf0>] (bus_add_driver) from [<c040406c>] (driver_register+0x78/0xf8)
     [<c040406c>] (driver_register) from [<c04f20a0>] (i2c_register_driver+0x34/0x84)
     [<c04f20a0>] (i2c_register_driver) from [<c01017d0>] (do_one_initcall+0x40/0x170)
     [<c01017d0>] (do_one_initcall) from [<c0a00dbc>] (kernel_init_freeable+0x15c/0x1fc)
     [<c0a00dbc>] (kernel_init_freeable) from [<c06e07b0>] (kernel_init+0x8/0x114)
     [<c06e07b0>] (kernel_init) from [<c0107978>] (ret_from_fork+0x14/0x3c)
     ---[ end trace 0919d3d0bc998260 ]---
    
     [snip..]
    
     Unable to handle kernel NULL pointer dereference at virtual address 00000078
     pgd = c0004000
     [00000078] *pgd=00000000
     Internal error: Oops: 5 [#1] PREEMPT SMP ARM
     Modules linked in:
     CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W       4.8.0-rc6-00154-g54fe84cbd50b #41
     Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
     task: ee874000 task.stack: ee878000
     PC is at down_write+0x14/0x54
     LR is at debugfs_remove_recursive+0x30/0x150
    
     [snip..]
    
     [<c06e489c>] (down_write) from [<c02e9954>] (debugfs_remove_recursive+0x30/0x150)
     [<c02e9954>] (debugfs_remove_recursive) from [<c0382b78>] (_regulator_put+0x24/0xac)
     [<c0382b78>] (_regulator_put) from [<c0382c1c>] (regulator_put+0x1c/0x2c)
     [<c0382c1c>] (regulator_put) from [<c0406434>] (release_nodes+0x16c/0x1dc)
     [<c0406434>] (release_nodes) from [<c04035d4>] (driver_probe_device+0xec/0x2c0)
     [<c04035d4>] (driver_probe_device) from [<c0403854>] (__driver_attach+0xac/0xb0)
     [<c0403854>] (__driver_attach) from [<c0401a74>] (bus_for_each_dev+0x68/0x9c)
     [<c0401a74>] (bus_for_each_dev) from [<c0402cf0>] (bus_add_driver+0x1a0/0x218)
     [<c0402cf0>] (bus_add_driver) from [<c040406c>] (driver_register+0x78/0xf8)
     [<c040406c>] (driver_register) from [<c04f20a0>] (i2c_register_driver+0x34/0x84)
     [<c04f20a0>] (i2c_register_driver) from [<c01017d0>] (do_one_initcall+0x40/0x170)
     [<c01017d0>] (do_one_initcall) from [<c0a00dbc>] (kernel_init_freeable+0x15c/0x1fc)
     [<c0a00dbc>] (kernel_init_freeable) from [<c06e07b0>] (kernel_init+0x8/0x114)
     [<c06e07b0>] (kernel_init) from [<c0107978>] (ret_from_fork+0x14/0x3c)
     Code: e1a04000 f590f000 e3a03001 e34f3fff (e1902f9f)
     ---[ end trace 0919d3d0bc998262 ]---
    
    --------x------------------x----------------
    
    Fix the kernel warnings and crashes by using regulator_bulk_get()
    instead of devm_regulator_bulk_get() and explicitly freeing the supplies
    in exit paths.
    
    Tested on Exynos 5250, dual core ARM A15 machine.
    Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
    Acked-by: default avatarCharles Keepax <ckeepax@opensource.wolfsonmicro.com>
    Signed-off-by: default avatarLee Jones <lee.jones@linaro.org>
    1a41741f
wm8994-core.c 16.4 KB