We will meet below issue due to mutex_lock() is called in interrupt context.
The mutex lock is used to protect the pattern trigger data, but before changing
new pattern trigger data (pattern values or repeat value) by users, we always
cancel the timer firstly to clear previous patterns' performance. That means
there is no race in pattern_trig_timer_function(), so we can drop the mutex
lock in pattern_trig_timer_function() to avoid this issue.

Moreover we can move the timer cancelling into mutex protection, since there
is no deadlock risk if we remove the mutex lock in pattern_trig_timer_function().

BUG: sleeping function called from invalid context at kernel/locking/mutex.c:254
in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper/1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted
4.20.0-rc1-koelsch-00841-ga338c8181013c1a9 #171
Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
[<c020f19c>] (unwind_backtrace) from [<c020aecc>] (show_stack+0x10/0x14)
[<c020aecc>] (show_stack) from [<c07affb8>] (dump_stack+0x7c/0x9c)
[<c07affb8>] (dump_stack) from [<c02417d4>] (___might_sleep+0xf4/0x158)
[<c02417d4>] (___might_sleep) from [<c07c92c4>] (mutex_lock+0x18/0x60)
[<c07c92c4>] (mutex_lock) from [<c067b28c>] (pattern_trig_timer_function+0x1c/0x11c)
[<c067b28c>] (pattern_trig_timer_function) from [<c027f6fc>] (call_timer_fn+0x1c/0x90)
[<c027f6fc>] (call_timer_fn) from [<c027f944>] (expire_timers+0x94/0xa4)
[<c027f944>] (expire_timers) from [<c027fc98>] (run_timer_softirq+0x108/0x15c)
[<c027fc98>] (run_timer_softirq) from [<c02021cc>] (__do_softirq+0x1d4/0x258)
[<c02021cc>] (__do_softirq) from [<c0224d24>] (irq_exit+0x64/0xc4)
[<c0224d24>] (irq_exit) from [<c0268dd0>] (__handle_domain_irq+0x80/0xb4)
[<c0268dd0>] (__handle_domain_irq) from [<c045e1b0>] (gic_handle_irq+0x58/0x90)
[<c045e1b0>] (gic_handle_irq) from [<c02019f8>] (__irq_svc+0x58/0x74)
Exception stack(0xeb483f60 to 0xeb483fa8)
3f60: 00000000 00000000 eb9afaa0 c0217e80 00000000 ffffe000 00000000 c0e06408
3f80: 00000002 c0e0647c c0c6a5f0 00000000 c0e04900 eb483fb0 c0207ea8 c0207e98
3fa0: 60020013 ffffffff
[<c02019f8>] (__irq_svc) from [<c0207e98>] (arch_cpu_idle+0x1c/0x38)
[<c0207e98>] (arch_cpu_idle) from [<c0247ca8>] (do_idle+0x138/0x268)
[<c0247ca8>] (do_idle) from [<c0248050>] (cpu_startup_entry+0x18/0x1c)
[<c0248050>] (cpu_startup_entry) from [<402022ec>] (0x402022ec)

Fixes: 5fd752b6

 ("leds: core: Introduce LED pattern trigger")
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>