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SubjectAT91: sama5d2: lockdep splat in sama5d2_pmc_of_clk_init_driver()
Dear Developers

Since upgrading to v5.2.2 from v5.1.x I keep getting lockdep complaints
(below) from clk initialization on SAMA5D2 board. Have you seen this?
Can you help me in finding a fix?

Best Regards,
Michał Mirosław

------- dmesg START ------

[ 0.000000] Booting Linux on physical CPU 0x0
[ 0.000000] Linux version 5.2.3+ (mirq@qmqm) (gcc version 8.3.0 (Debian 8.3.0-2)) #312 Fri Jul 26 15:32:06 CEST 2019
[ 0.000000] CPU: ARMv7 Processor [410fc051] revision 1 (ARMv7), cr=10c53c7d
[ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
[ 0.000000] OF: fdt: Machine model: SAMA5D2 proto3
[ 0.000000] printk: bootconsole [earlycon0] enabled
[ 0.000000] Memory policy: Data cache writeback
[ 0.000000] On node 0 totalpages: 65536
[ 0.000000] Normal zone: 512 pages used for memmap
[ 0.000000] Normal zone: 0 pages reserved
[ 0.000000] Normal zone: 65536 pages, LIFO batch:15
[ 0.000000] CPU: All CPU(s) started in SVC mode.
[ 0.000000] pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
[ 0.000000] pcpu-alloc: [0] 0
[ 0.000000] Built 1 zonelists, mobility grouping on. Total pages: 65024
[ 0.000000] Kernel command line: console=ttyS0,115200 root=/dev/mmcblk0p1 rootfstype=squashfs debug loglevel=9 earlyprintk
[ 0.000000] Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
[ 0.000000] Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
[ 0.000000] Memory: 239752K/262144K available (8192K kernel code, 578K rwdata, 2312K rodata, 1024K init, 7103K bss, 22392K reserved, 0K cma-reserved)
[ 0.000000] ftrace: allocating 25429 entries in 50 pages
[ 0.000000] Running RCU self tests
[ 0.000000] NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16
[ 0.000000] L2C-310 ID prefetch enabled, offset 2 lines
[ 0.000000] L2C-310 dynamic clock gating enabled, standby mode enabled
[ 0.000000] L2C-310 cache controller enabled, 8 ways, 128 kB
[ 0.000000] L2C-310: CACHE_ID 0x410000c9, AUX_CTRL 0x36020000
[ 0.000000] random: get_random_bytes called from start_kernel+0x2b8/0x450 with crng_init=0

[ 0.000000] ======================================================
[ 0.000000] WARNING: possible circular locking dependency detected
[ 0.000000] 5.2.3+ #312 Not tainted
[ 0.000000] ------------------------------------------------------
[ 0.000000] swapper/0 is trying to acquire lock:
[ 0.000000] (ptrval) (pmc_pcr_lock){....}, at: clk_sam9x5_peripheral_enable+0x28/0xac
[ 0.000000]
but task is already holding lock:
[ 0.000000] (ptrval) (enable_lock){....}, at: clk_enable_lock+0x38/0xf4
[ 0.000000]
which lock already depends on the new lock.

[ 0.000000]
the existing dependency chain (in reverse order) is:
[ 0.000000]
-> #2 (enable_lock){....}:
[ 0.000000] clk_enable_lock+0x38/0xf4
[ 0.000000] clk_core_enable_lock+0x14/0x34
[ 0.000000] regmap_mmio_read+0x54/0x6c
[ 0.000000] _regmap_read+0x68/0x160
[ 0.000000] regmap_read+0x44/0x64
[ 0.000000] at91_clk_register_sam9x5_main+0xb0/0x108
[ 0.000000] sama5d2_pmc_of_clk_init_driver+0x15c/0x654
[ 0.000000] of_clk_init+0x154/0x21c
[ 0.000000] time_init+0x30/0x38
[ 0.000000] start_kernel+0x2ec/0x450
[ 0.000000] 0x0
[ 0.000000]
-> #1 (syscon:113:(&syscon_config)->lock){....}:
[ 0.000000] regmap_lock_spinlock+0x14/0x1c
[ 0.000000] regmap_write+0x34/0x64
[ 0.000000] clk_sam9x5_peripheral_recalc_rate+0x60/0xf4
[ 0.000000] __clk_register+0x28c/0x7f4
[ 0.000000] clk_hw_register+0x20/0x2c
[ 0.000000] at91_clk_register_sam9x5_peripheral+0xec/0x14c
[ 0.000000] sama5d2_pmc_of_clk_init_driver+0x42c/0x654
[ 0.000000] of_clk_init+0x154/0x21c
[ 0.000000] time_init+0x30/0x38
[ 0.000000] start_kernel+0x2ec/0x450
[ 0.000000] 0x0
[ 0.000000]
-> #0 (pmc_pcr_lock){....}:
[ 0.000000] _raw_spin_lock_irqsave+0x44/0x58
[ 0.000000] clk_sam9x5_peripheral_enable+0x28/0xac
[ 0.000000] clk_core_enable+0x88/0x258
[ 0.000000] clk_core_enable_lock+0x20/0x34
[ 0.000000] clk_prepare_enable+0x1c/0x34
[ 0.000000] tcb_clksrc_init+0x13c/0x4b8
[ 0.000000] timer_probe+0x78/0xe0
[ 0.000000] start_kernel+0x2ec/0x450
[ 0.000000] 0x0
[ 0.000000]
other info that might help us debug this:

[ 0.000000] Chain exists of:
pmc_pcr_lock --> syscon:113:(&syscon_config)->lock --> enable_lock

[ 0.000000] Possible unsafe locking scenario:

[ 0.000000] CPU0 CPU1
[ 0.000000] ---- ----
[ 0.000000] lock(enable_lock);
[ 0.000000] lock(syscon:113:(&syscon_config)->lock);
[ 0.000000] lock(enable_lock);
[ 0.000000] lock(pmc_pcr_lock);
[ 0.000000]
*** DEADLOCK ***

[ 0.000000] 1 lock held by swapper/0:
[ 0.000000] #0: (ptrval) (enable_lock){....}, at: clk_enable_lock+0x38/0xf4
[ 0.000000]
stack backtrace:
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.2.3+ #312
[ 0.000000] Hardware name: Atmel SAMA5
[ 0.000000] [<c010edc0>] (unwind_backtrace) from [<c010c1a8>] (show_stack+0x18/0x1c)
[ 0.000000] [<c010c1a8>] (show_stack) from [<c01515c4>] (print_circular_bug+0x220/0x25c)
[ 0.000000] [<c01515c4>] (print_circular_bug) from [<c0154264>] (__lock_acquire+0x1600/0x1a80)
[ 0.000000] [<c0154264>] (__lock_acquire) from [<c0154f08>] (lock_acquire+0xc4/0x168)
[ 0.000000] [<c0154f08>] (lock_acquire) from [<c08330a8>] (_raw_spin_lock_irqsave+0x44/0x58)
[ 0.000000] [<c08330a8>] (_raw_spin_lock_irqsave) from [<c042fabc>] (clk_sam9x5_peripheral_enable+0x28/0xac)
[ 0.000000] [<c042fabc>] (clk_sam9x5_peripheral_enable) from [<c0424990>] (clk_core_enable+0x88/0x258)
[ 0.000000] [<c0424990>] (clk_core_enable) from [<c0425c4c>] (clk_core_enable_lock+0x20/0x34)
[ 0.000000] [<c0425c4c>] (clk_core_enable_lock) from [<c058d788>] (clk_prepare_enable+0x1c/0x34)
[ 0.000000] [<c058d788>] (clk_prepare_enable) from [<c0c358bc>] (tcb_clksrc_init+0x13c/0x4b8)
[ 0.000000] [<c0c358bc>] (tcb_clksrc_init) from [<c0c35718>] (timer_probe+0x78/0xe0)
[ 0.000000] [<c0c35718>] (timer_probe) from [<c0c00dc4>] (start_kernel+0x2ec/0x450)
[ 0.000000] [<c0c00dc4>] (start_kernel) from [<00000000>] (0x0)
[ 0.000000] clocksource: timer@f800c000: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 184217874325 ns
[ 0.000021] sched_clock: 32 bits at 10MHz, resolution 96ns, wraps every 206986376143ns
[ 0.009762] Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar
[ 0.018365] ... MAX_LOCKDEP_SUBCLASSES: 8
[ 0.022911] ... MAX_LOCK_DEPTH: 48
[ 0.027546] ... MAX_LOCKDEP_KEYS: 8191
[ 0.032367] ... CLASSHASH_SIZE: 4096
[ 0.037190] ... MAX_LOCKDEP_ENTRIES: 32768
[ 0.042109] ... MAX_LOCKDEP_CHAINS: 65536
[ 0.047028] ... CHAINHASH_SIZE: 32768
[ 0.051944] memory used by lock dependency info: 4411 kB
[ 0.057913] per task-struct memory footprint: 1536 bytes
[ 0.063965] Calibrating delay loop... 358.40 BogoMIPS (lpj=179200)
[ 0.081133] pid_max: default: 32768 minimum: 301
[ 0.086831] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.094201] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.104331] CPU: Testing write buffer coherency: ok
[ 0.112611] Setting up static identity map for 0x20100000 - 0x20100060
[ 0.122704] devtmpfs: initialized
[ 0.151047] VFP support v0.3: implementor 41 architecture 2 part 30 variant 5 rev 1
[ 0.160466] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275000 ns
[ 0.171341] futex hash table entries: 256 (order: 1, 11264 bytes)
[ 0.178738] pinctrl core: initialized pinctrl subsystem
[ 0.186405] regulator-dummy: no parameters, enabled
[ 0.194206] NET: Registered protocol family 16
[ 0.207208] DMA: preallocated 256 KiB pool for atomic coherent allocations
[ 0.292223] AT91: PM: standby: standby, suspend: ulp0
[ 0.300092] atmel_tcb: probe of f800c000.timer failed with error -16
[ 0.422319] random: fast init done
[ 0.496218] at_xdmac f0010000.dma-controller: 16 channels, mapped at 0x(ptrval)
[ 0.511573] at_xdmac f0004000.dma-controller: 16 channels, mapped at 0x(ptrval)
[ 0.521731] AT91: Detected SoC family: sama5d2
[ 0.526738] AT91: Detected SoC: sama5d27, revision 2
[...]

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