cpu:
allwinner h3(cortex-a7)

Phenomenon:
cpu is enabled ondemand cpufreq frequency modulation, there is no such problem when frequency modulation is not enabled
The cpu will be stuck for a period of time in the stuck place described below, and it will recover after a while

Code location::
https://elixir.bootlin.com/linux/v4.19.206/source/drivers/usb/core/hcd.c#L1771

By analyzing the perf output file, __usb_hcd_giveback_urb() will get stuck in these places:
c04d35bc __usb_hcd_giveback_urb+0x60 ([kernel.kallsyms]): 1586 times
c04d35f4 __usb_hcd_giveback_urb+0x98 ([kernel.kallsyms]): 1 time
c04d3590 __usb_hcd_giveback_urb+0x34 ([kernel.kallsyms]): 4 times
c04d3574 __usb_hcd_giveback_urb+0x18 ([kernel.kallsyms]): 1 time
c04d3580 __usb_hcd_giveback_urb+0x24 ([kernel.kallsyms]): 1 time
c04d3598 __usb_hcd_giveback_urb+0x3c ([kernel.kallsyms]): 1 time
The less frequent ones are ignored

0000084c <__usb_hcd_giveback_urb>:
     84c:   e92d4070    push    {r4, r5, r6, lr}
     850:   e3a03000    mov r3, #0
     854:   e590103c    ldr r1, [r0, #60]   ; 0x3c
     858:   e1a04000    mov r4, r0
     85c:   e5902028    ldr r2, [r0, #40]   ; 0x28
     860:   e3110001    tst r1, #1
     864:   e5905024    ldr r5, [r0, #36]   ; 0x24
     868:   e5906010    ldr r6, [r0, #16]
     86c:   e592003c    ldr r0, [r2, #60]   ; 0x3c
     870:   e5843004    str r3, [r4, #4]
     874:   1a00001b    bne 8e8 <__usb_hcd_giveback_urb+0x9c>
     878:   e1a01004    mov r1, r4
     87c:   ebffffe1    bl  808 <unmap_urb_for_dma>
     880:   e1a00005    mov r0, r5
     884:   ebfffffe    bl  0 <usb_anchor_suspend_wakeups>
     888:   e1a00004    mov r0, r4
     88c:   ebfffffe    bl  0 <usb_unanchor_urb>
     890:   e5846038    str r6, [r4, #56]   ; 0x38
     894:   e10f6000    mrs r6, CPSR
     898:   f10c0080    cpsid   i
     89c:   e5943078    ldr r3, [r4, #120]  ; 0x78
     8a0:   e1a00004    mov r0, r4
     8a4:   e12fff33    blx r3
     8a8:   e121f006    msr CPSR_c, r6 <----------corresponding statement local_irq_restore(flags);
     8ac:   e1a00005    mov r0, r5  <-------------__usb_hcd_giveback_urb+0x60
     8b0:   ebfffffe    bl  0 <usb_anchor_resume_wakeups>
     8b4:   e2843008    add r3, r4, #8
     8b8:   f593f000    pldw    [r3]
     8bc:   e1932f9f    ldrex   r2, [r3]
     8c0:   e2422001    sub r2, r2, #1
     8c4:   e1831f92    strex   r1, r2, [r3]
     8c8:   e3310000    teq r1, #0
     8cc:   1afffffa    bne 8bc <__usb_hcd_giveback_urb+0x70>
     8d0:   e594300c    ldr r3, [r4, #12]
     8d4:   e3530000    cmp r3, #0
     8d8:   1a00000c    bne 910 <__usb_hcd_giveback_urb+0xc4>
     8dc:   e1a00004    mov r0, r4
     8e0:   e8bd4070    pop {r4, r5, r6, lr}
     8e4:   eafffffe    b   0 <usb_free_urb>
     8e8:   e5941058    ldr r1, [r4, #88]   ; 0x58
     8ec:   e5942054    ldr r2, [r4, #84]   ; 0x54
     8f0:   e1510002    cmp r1, r2
     8f4:   23a03000    movcs   r3, #0
     8f8:   33a03001    movcc   r3, #1
     8fc:   e3560000    cmp r6, #0
     900:   13a03000    movne   r3, #0
     904:   e3530000    cmp r3, #0
     908:   13e06078    mvnne   r6, #120    ; 0x78
     90c:   eaffffd9    b   878 <__usb_hcd_giveback_urb+0x2c>
     910:   e3000000    movw    r0, #0
     914:   e3a03000    mov r3, #0
     918:   e3400000    movt    r0, #0
     91c:   e3a02001    mov r2, #1
     920:   e3a01003    mov r1, #3
     924:   ebfffffe    bl  0 <__wake_up>
     928:   e1a00004    mov r0, r4
     92c:   e8bd4070    pop {r4, r5, r6, lr}
     930:   eafffffe    b   0 <usb_free_urb>

Because perf is based on interrupts, it takes a long time to turn off the interrupt.
After the interrupt is turned on, the perf event is triggered.

After commenting out the local_irq_save() and local_irq_restore() here, it is still stuck.
The perf flame graph shows that the function that mainly eats the cpu is mmiocpy()


sample call stack:
swapper     0 [000]   938.366296:    1642083 cycles:ppp: 
            c070ad4c mmiocpy+0x4c ([kernel.kallsyms])
            bf025558 uvc_video_decode_data.constprop.5+0x38 (/lib/modules/4.19.173/kernel/drivers/media/usb/uvc/uvcvideo.ko)
            bf025610 uvc_video_decode_isoc+0x6c (/lib/modules/4.19.173/kernel/drivers/media/usb/uvc/uvcvideo.ko)
            bf0242a0 uvc_video_complete+0xb0 (/lib/modules/4.19.173/kernel/drivers/media/usb/uvc/uvcvideo.ko)
            c04d35b0 __usb_hcd_giveback_urb+0x54 ([kernel.kallsyms])
            c04d36e4 usb_giveback_urb_bh+0xac ([kernel.kallsyms])
            c0122070 tasklet_action_common.constprop.3+0x64 ([kernel.kallsyms])
            c01021fc __softirqentry_text_start+0x114 ([kernel.kallsyms])
            c0122400 irq_exit+0xcc ([kernel.kallsyms])
            c0162634 __handle_domain_irq+0x60 ([kernel.kallsyms])
            c0390a34 gic_handle_irq+0x4c ([kernel.kallsyms])
            c0101a0c __irq_svc+0x6c ([kernel.kallsyms])
            c01087e8 arch_cpu_idle+0x38 ([kernel.kallsyms])
            c0145d78 do_idle+0xe4 ([kernel.kallsyms])
            c0146070 cpu_startup_entry+0x18 ([kernel.kallsyms])
            c0a00cb8 start_kernel+0x3dc ([kernel.kallsyms])

count statistics:

42	mmiocpy+0x31c
42	mmiocpy+0xf0
210	mmiocpy+0x2b8
229	mmiocpy+0x208
235	mmiocpy+0x2ac
247	mmiocpy+0x1fc
271	mmiocpy+0x158
277	mmiocpy+0x14c
380	mmiocpy+0x4c

The last few passes are the stuck points caused by ldm r1!, {...} loading registers from memory.
This shows that the cpu core and the memory controller are not compatible with each other.

mmiocpy == memcpy, disassembly:

arch/arm/lib/memcpy.o:     file format elf32-littlearm
Disassembly of section .text:
00000000 <memcpy>:
   0:	e92d4011 	push	{r0, r4, lr}
   4:	e2522004 	subs	r2, r2, #4
   8:	ba00002b 	blt	bc <memcpy+0xbc>
   c:	e210c003 	ands	ip, r0, #3
  10:	f5d1f000 	pld	[r1]
  14:	1a000030 	bne	dc <memcpy+0xdc>
  18:	e211c003 	ands	ip, r1, #3
  1c:	1a00003a 	bne	10c <memcpy+0x10c>
  20:	e252201c 	subs	r2, r2, #28
  24:	e92d01e0 	push	{r5, r6, r7, r8}
  28:	ba00000c 	blt	60 <memcpy+0x60>
  2c:	f5d1f000 	pld	[r1]
  30:	e2522060 	subs	r2, r2, #96	; 0x60
  34:	f5d1f01c 	pld	[r1, #28]
  38:	ba000002 	blt	48 <memcpy+0x48>
  3c:	f5d1f03c 	pld	[r1, #60]	; 0x3c
  40:	f5d1f05c 	pld	[r1, #92]	; 0x5c
  44:	f5d1f07c 	pld	[r1, #124]	; 0x7c
  48:	e8b151f8 	ldm	r1!, {r3, r4, r5, r6, r7, r8, ip, lr} <------------------Load the register list from [r1]
  4c:	e2522020 	subs	r2, r2, #32
  50:	e8a051f8 	stmia	r0!, {r3, r4, r5, r6, r7, r8, ip, lr}
  54:	aafffffa 	bge	44 <memcpy+0x44>
  58:	e3720060 	cmn	r2, #96	; 0x60
  5c:	aafffff9 	bge	48 <memcpy+0x48>
  60:	e212c01c 	ands	ip, r2, #28
  64:	e26cc020 	rsb	ip, ip, #32
  68:	108ff00c 	addne	pc, pc, ip
  6c:	ea000011 	b	b8 <memcpy+0xb8>
  70:	e320f000 	nop	{0}
  74:	e4913004 	ldr	r3, [r1], #4
  78:	e4914004 	ldr	r4, [r1], #4
  7c:	e4915004 	ldr	r5, [r1], #4
  80:	e4916004 	ldr	r6, [r1], #4
  84:	e4917004 	ldr	r7, [r1], #4
  88:	e4918004 	ldr	r8, [r1], #4
  8c:	e491e004 	ldr	lr, [r1], #4
  90:	e08ff00c 	add	pc, pc, ip
  94:	e320f000 	nop	{0}
  98:	e320f000 	nop	{0}
  9c:	e4803004 	str	r3, [r0], #4
  a0:	e4804004 	str	r4, [r0], #4
  a4:	e4805004 	str	r5, [r0], #4
  a8:	e4806004 	str	r6, [r0], #4
  ac:	e4807004 	str	r7, [r0], #4
  b0:	e4808004 	str	r8, [r0], #4
  b4:	e480e004 	str	lr, [r0], #4
  b8:	e8bd01e0 	pop	{r5, r6, r7, r8}
  bc:	e1b02f82 	lsls	r2, r2, #31
  c0:	14d13001 	ldrbne	r3, [r1], #1
  c4:	24d14001 	ldrbcs	r4, [r1], #1
  c8:	24d1c001 	ldrbcs	ip, [r1], #1
  cc:	14c03001 	strbne	r3, [r0], #1
  d0:	24c04001 	strbcs	r4, [r0], #1
  d4:	24c0c001 	strbcs	ip, [r0], #1
  d8:	e8bd8011 	pop	{r0, r4, pc}
  dc:	e26cc004 	rsb	ip, ip, #4
  e0:	e35c0002 	cmp	ip, #2
  e4:	c4d13001 	ldrbgt	r3, [r1], #1
  e8:	a4d14001 	ldrbge	r4, [r1], #1
  ec:	e4d1e001 	ldrb	lr, [r1], #1
  f0:	c4c03001 	strbgt	r3, [r0], #1
  f4:	a4c04001 	strbge	r4, [r0], #1
  f8:	e052200c 	subs	r2, r2, ip
  fc:	e4c0e001 	strb	lr, [r0], #1
 100:	baffffed 	blt	bc <memcpy+0xbc>
 104:	e211c003 	ands	ip, r1, #3
 108:	0affffc4 	beq	20 <memcpy+0x20>
 10c:	e3c11003 	bic	r1, r1, #3
 110:	e35c0002 	cmp	ip, #2
 114:	e491e004 	ldr	lr, [r1], #4
 118:	0a00002c 	beq	1d0 <memcpy+0x1d0>
 11c:	ca000057 	bgt	280 <memcpy+0x280>
 120:	e252201c 	subs	r2, r2, #28
 124:	ba00001f 	blt	1a8 <memcpy+0x1a8>
 128:	e92d03e0 	push	{r5, r6, r7, r8, r9}
 12c:	f5d1f000 	pld	[r1]
 130:	e2522060 	subs	r2, r2, #96	; 0x60
 134:	f5d1f01c 	pld	[r1, #28]
 138:	ba000002 	blt	148 <memcpy+0x148>
 13c:	f5d1f03c 	pld	[r1, #60]	; 0x3c
 140:	f5d1f05c 	pld	[r1, #92]	; 0x5c
 144:	f5d1f07c 	pld	[r1, #124]	; 0x7c
 148:	e8b100f0 	ldm	r1!, {r4, r5, r6, r7}  <------------------Load the register list from [r1]
 14c:	e1a0342e 	lsr	r3, lr, #8
 150:	e2522020 	subs	r2, r2, #32
 154:	e8b15300 	ldm	r1!, {r8, r9, ip, lr} <------------------Load the register list from [r1]
 158:	e1833c04 	orr	r3, r3, r4, lsl #24
 15c:	e1a04424 	lsr	r4, r4, #8
 160:	e1844c05 	orr	r4, r4, r5, lsl #24
 164:	e1a05425 	lsr	r5, r5, #8
 168:	e1855c06 	orr	r5, r5, r6, lsl #24
 16c:	e1a06426 	lsr	r6, r6, #8
 170:	e1866c07 	orr	r6, r6, r7, lsl #24
 174:	e1a07427 	lsr	r7, r7, #8
 178:	e1877c08 	orr	r7, r7, r8, lsl #24
 17c:	e1a08428 	lsr	r8, r8, #8
 180:	e1888c09 	orr	r8, r8, r9, lsl #24
 184:	e1a09429 	lsr	r9, r9, #8
 188:	e1899c0c 	orr	r9, r9, ip, lsl #24
 18c:	e1a0c42c 	lsr	ip, ip, #8
 190:	e18ccc0e 	orr	ip, ip, lr, lsl #24
 194:	e8a013f8 	stmia	r0!, {r3, r4, r5, r6, r7, r8, r9, ip}
 198:	aaffffe9 	bge	144 <memcpy+0x144>
 19c:	e3720060 	cmn	r2, #96	; 0x60
 1a0:	aaffffe8 	bge	148 <memcpy+0x148>
 1a4:	e8bd03e0 	pop	{r5, r6, r7, r8, r9}
 1a8:	e212c01c 	ands	ip, r2, #28
 1ac:	0a000005 	beq	1c8 <memcpy+0x1c8>
 1b0:	e1a0342e 	lsr	r3, lr, #8
 1b4:	e491e004 	ldr	lr, [r1], #4
 1b8:	e25cc004 	subs	ip, ip, #4
 1bc:	e1833c0e 	orr	r3, r3, lr, lsl #24
 1c0:	e4803004 	str	r3, [r0], #4
 1c4:	cafffff9 	bgt	1b0 <memcpy+0x1b0>
 1c8:	e2411003 	sub	r1, r1, #3
 1cc:	eaffffba 	b	bc <memcpy+0xbc>
 1d0:	e252201c 	subs	r2, r2, #28
 1d4:	ba00001f 	blt	258 <memcpy+0x258>
 1d8:	e92d03e0 	push	{r5, r6, r7, r8, r9}
 1dc:	f5d1f000 	pld	[r1]
 1e0:	e2522060 	subs	r2, r2, #96	; 0x60
 1e4:	f5d1f01c 	pld	[r1, #28]
 1e8:	ba000002 	blt	1f8 <memcpy+0x1f8>
 1ec:	f5d1f03c 	pld	[r1, #60]	; 0x3c
 1f0:	f5d1f05c 	pld	[r1, #92]	; 0x5c
 1f4:	f5d1f07c 	pld	[r1, #124]	; 0x7c
 1f8:	e8b100f0 	ldm	r1!, {r4, r5, r6, r7} <------------------Load the register list from [r1]
 1fc:	e1a0382e 	lsr	r3, lr, #16
 200:	e2522020 	subs	r2, r2, #32
 204:	e8b15300 	ldm	r1!, {r8, r9, ip, lr}
 208:	e1833804 	orr	r3, r3, r4, lsl #16
 20c:	e1a04824 	lsr	r4, r4, #16
 210:	e1844805 	orr	r4, r4, r5, lsl #16
 214:	e1a05825 	lsr	r5, r5, #16
 218:	e1855806 	orr	r5, r5, r6, lsl #16
 21c:	e1a06826 	lsr	r6, r6, #16
 220:	e1866807 	orr	r6, r6, r7, lsl #16
 224:	e1a07827 	lsr	r7, r7, #16
 228:	e1877808 	orr	r7, r7, r8, lsl #16
 22c:	e1a08828 	lsr	r8, r8, #16
 230:	e1888809 	orr	r8, r8, r9, lsl #16
 234:	e1a09829 	lsr	r9, r9, #16
 238:	e189980c 	orr	r9, r9, ip, lsl #16
 23c:	e1a0c82c 	lsr	ip, ip, #16
 240:	e18cc80e 	orr	ip, ip, lr, lsl #16
 244:	e8a013f8 	stmia	r0!, {r3, r4, r5, r6, r7, r8, r9, ip}
 248:	aaffffe9 	bge	1f4 <memcpy+0x1f4>
 24c:	e3720060 	cmn	r2, #96	; 0x60
 250:	aaffffe8 	bge	1f8 <memcpy+0x1f8>
 254:	e8bd03e0 	pop	{r5, r6, r7, r8, r9}
 258:	e212c01c 	ands	ip, r2, #28
 25c:	0a000005 	beq	278 <memcpy+0x278>
 260:	e1a0382e 	lsr	r3, lr, #16
 264:	e491e004 	ldr	lr, [r1], #4
 268:	e25cc004 	subs	ip, ip, #4
 26c:	e183380e 	orr	r3, r3, lr, lsl #16
 270:	e4803004 	str	r3, [r0], #4
 274:	cafffff9 	bgt	260 <memcpy+0x260>
 278:	e2411002 	sub	r1, r1, #2
 27c:	eaffff8e 	b	bc <memcpy+0xbc>
 280:	e252201c 	subs	r2, r2, #28
 284:	ba00001f 	blt	308 <memcpy+0x308>
 288:	e92d03e0 	push	{r5, r6, r7, r8, r9}
 28c:	f5d1f000 	pld	[r1]
 290:	e2522060 	subs	r2, r2, #96	; 0x60
 294:	f5d1f01c 	pld	[r1, #28]
 298:	ba000002 	blt	2a8 <memcpy+0x2a8>
 29c:	f5d1f03c 	pld	[r1, #60]	; 0x3c
 2a0:	f5d1f05c 	pld	[r1, #92]	; 0x5c
 2a4:	f5d1f07c 	pld	[r1, #124]	; 0x7c
 2a8:	e8b100f0 	ldm	r1!, {r4, r5, r6, r7}
 2ac:	e1a03c2e 	lsr	r3, lr, #24
 2b0:	e2522020 	subs	r2, r2, #32
 2b4:	e8b15300 	ldm	r1!, {r8, r9, ip, lr}
 2b8:	e1833404 	orr	r3, r3, r4, lsl #8
 2bc:	e1a04c24 	lsr	r4, r4, #24
 2c0:	e1844405 	orr	r4, r4, r5, lsl #8
 2c4:	e1a05c25 	lsr	r5, r5, #24
 2c8:	e1855406 	orr	r5, r5, r6, lsl #8
 2cc:	e1a06c26 	lsr	r6, r6, #24
 2d0:	e1866407 	orr	r6, r6, r7, lsl #8
 2d4:	e1a07c27 	lsr	r7, r7, #24
 2d8:	e1877408 	orr	r7, r7, r8, lsl #8
 2dc:	e1a08c28 	lsr	r8, r8, #24
 2e0:	e1888409 	orr	r8, r8, r9, lsl #8
 2e4:	e1a09c29 	lsr	r9, r9, #24
 2e8:	e189940c 	orr	r9, r9, ip, lsl #8
 2ec:	e1a0cc2c 	lsr	ip, ip, #24
 2f0:	e18cc40e 	orr	ip, ip, lr, lsl #8
 2f4:	e8a013f8 	stmia	r0!, {r3, r4, r5, r6, r7, r8, r9, ip}
 2f8:	aaffffe9 	bge	2a4 <memcpy+0x2a4>
 2fc:	e3720060 	cmn	r2, #96	; 0x60
 300:	aaffffe8 	bge	2a8 <memcpy+0x2a8>
 304:	e8bd03e0 	pop	{r5, r6, r7, r8, r9}
 308:	e212c01c 	ands	ip, r2, #28
 30c:	0a000005 	beq	328 <memcpy+0x328>
 310:	e1a03c2e 	lsr	r3, lr, #24
 314:	e491e004 	ldr	lr, [r1], #4
 318:	e25cc004 	subs	ip, ip, #4
 31c:	e183340e 	orr	r3, r3, lr, lsl #8
 320:	e4803004 	str	r3, [r0], #4
 324:	cafffff9 	bgt	310 <memcpy+0x310>
 328:	e2411001 	sub	r1, r1, #1
 32c:	eaffff62 	b	bc <memcpy+0xbc>