The OPP list needs to be protected against concurrent accesses. Using
simple RCU read locks does the trick and gets rid of the following
lockdep warning:
===============================
[ INFO: suspicious RCU usage. ]
4.2.0-next-20150908 #1 Not tainted
-------------------------------
drivers/base/power/opp.c:460 Missing rcu_read_lock() or dev_opp_list_lock protection!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 0
4 locks held by kworker/u8:0/6:
#0: ("%s""deferwq"){++++.+}, at: [<c0040d8c>] process_one_work+0x118/0x4bc
#1: (deferred_probe_work){+.+.+.}, at: [<c0040d8c>] process_one_work+0x118/0x4bc
#2: (&dev->mutex){......}, at: [<c03b8194>] __device_attach+0x20/0x118
#3: (prepare_lock){+.+...}, at: [<c054bc08>] clk_prepare_lock+0x10/0xf8
stack backtrace:
CPU: 2 PID: 6 Comm: kworker/u8:0 Not tainted 4.2.0-next-20150908 #1
Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
Workqueue: deferwq deferred_probe_work_func
[<c001802c>] (unwind_backtrace) from [<c00135a4>] (show_stack+0x10/0x14)
[<c00135a4>] (show_stack) from [<c02a8418>] (dump_stack+0x94/0xd4)
[<c02a8418>] (dump_stack) from [<c03c6f6c>] (dev_pm_opp_find_freq_ceil+0x108/0x114)
[<c03c6f6c>] (dev_pm_opp_find_freq_ceil) from [<c0551a3c>] (dfll_calculate_rate_request+0xb8/0x170)
[<c0551a3c>] (dfll_calculate_rate_request) from [<c0551b10>] (dfll_clk_round_rate+0x1c/0x2c)
[<c0551b10>] (dfll_clk_round_rate) from [<c054de2c>] (clk_calc_new_rates+0x1b8/0x228)
[<c054de2c>] (clk_calc_new_rates) from [<c054e44c>] (clk_core_set_rate_nolock+0x44/0xac)
[<c054e44c>] (clk_core_set_rate_nolock) from [<c054e4d8>] (clk_set_rate+0x24/0x34)
[<c054e4d8>] (clk_set_rate) from [<c0512460>] (tegra124_cpufreq_probe+0x120/0x230)
[<c0512460>] (tegra124_cpufreq_probe) from [<c03b9cbc>] (platform_drv_probe+0x44/0xac)
[<c03b9cbc>] (platform_drv_probe) from [<c03b84c8>] (driver_probe_device+0x218/0x304)
[<c03b84c8>] (driver_probe_device) from [<c03b69b0>] (bus_for_each_drv+0x60/0x94)
[<c03b69b0>] (bus_for_each_drv) from [<c03b8228>] (__device_attach+0xb4/0x118)
ata1: SATA link down (SStatus 0 SControl 300)
[<c03b8228>] (__device_attach) from [<c03b77c8>] (bus_probe_device+0x88/0x90)
[<c03b77c8>] (bus_probe_device) from [<c03b7be8>] (deferred_probe_work_func+0x58/0x8c)
[<c03b7be8>] (deferred_probe_work_func) from [<c0040dfc>] (process_one_work+0x188/0x4bc)
[<c0040dfc>] (process_one_work) from [<c004117c>] (worker_thread+0x4c/0x4f4)
[<c004117c>] (worker_thread) from [<c0047230>] (kthread+0xe4/0xf8)
[<c0047230>] (kthread) from [<c000f7d0>] (ret_from_fork+0x14/0x24)
Signed-off-by: Thierry Reding <treding@nvidia.com>
Fixes: c4fe70ada4 ("clk: tegra: Add closed loop support for the DFLL")
[vince.h@nvidia.com: Unlock rcu on error path]
Signed-off-by: Vince Hsu <vince.h@nvidia.com>
[sboyd@codeaurora.org: Dropped second hunk that nested the rcu
read lock unnecessarily]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
e1595d89ae