DailyBread

https://en.wikipedia.org/wiki/Disk_encryption_theory#XTS

https://www.kingston.com/en/blog/data-security/xts-encryption 

• XTS provides greater data protection over other block cipher modes, such as CBC and ECB.
• It eliminates potential vulnerabilities associated with some of the more sophisticated side channel attacks that could be used to exploit weaknesses within other modes.
• XTS uses two AES keys. One key is used to perform the AES block encryption; the other is used to encrypt what is known as a "Tweak Value."
• Since each block is independent and there is no chaining, if the stored cipher data is damaged and becomes corrupted, only the data for that particular block will be unrecoverable. 

dma_handle 포인터와 cpu_addr 를 각각 관리하는 이유

1. DMA 장치와 CPU 간의 메모리 구조의 차이: 일반적으로 DMA 장치는 메모리에 직접 접근하여 데이터를 전송합니다. 이 때 DMA 장치는 메모리 주소 공간을 CPU가 사용하는 것과 다르게 볼 수 있습니다. 예를 들어, 일부 시스템에서는 DMA 장치가 접근할 수 있는 주소 공간이 제한되어 있거나 물리적인 주소 공간이 특정한 형식을 따를 수 있습니다. 그러므로 DMA 장치가 접근하는 주소와 CPU가 접근하는 주소가 다를 수 있습니다.
2. 캐시 일관성(Cache Coherency): 많은 시스템에서 CPU는 캐시를 사용하여 성능을 향상시킵니다. 그러나 DMA 장치는 이러한 캐시 구조에 직접적으로 접근할 수 없기 때문에, CPU가 쓴 데이터가 캐시에 존재하는 경우에도 DMA 장치에서 해당 데이터를 읽을 때 문제가 발생할 수 있습니다. 이를 해결하기 위해서는 DMA 전송 전에 캐시를 플러시하거나(invalidate) DMA 전송 후에 캐시를 재설정해야 할 수 있습니다. 이러한 캐시 일관성 문제를 해결하기 위해 DMA 할당 함수는 CPU가 접근하는 메모리 주소와 DMA 장치가 접근하는 메모리 주소를 따로 관리합니다. 이를 통해 DMA 전송 시에 캐시 일관성을 유지할 수 있습니다.

Check the process who is using the mounted path

fuser -cu mount_path

Kill the process

fuser -ck mount_path

from U-boot console

#> ums 0 mmc 0

// dwc3 init

set_state_simple op missing
UMS: LUN 0, dev 0, hwpart 0, sector 0x0, count 0x1d1f000
dwc3_alloc_event_buffers
dwc3_alloc_one_event_buffer
dwc3_core_init
dwc3_core_soft_reset
found 10 IN and 6 OUT endpoints
dwc3_alloc_scratch_buffers
dwc3_setup_scratch_buffers
dwc3_event_buffers_setup
Event buf 00000000eb5762c0 dma eb5762c0 length 256
dwc3_set_mode 2
dwc3_gadget_init
dwc3_uboot_init DONE
g_dnl_register g_dnl_driver.name = usb_dnl_ums
usb_composite_register
usb_gadget_register_driver
usb_gadget_probe_driver found
udc_bind_to_driver registering UDC driver [<NULL>]
registering UDC driver [<NULL>]
udc_bind_to_driver driver->speed 3
g_dnl_bind
g_dnl_bind gadget: 0x00000000eb579290 cdev: 0x00000000eb57c9e0
usb_gadget_connect

// D+ High for USB2.0

dwc3_gadget_run_stop is_on[1]
usb_gadget_udc_start
usb_gadget_connect
dwc3_gadget_run_stop is_on[1]

Connect USB line to a host 

// DWC3_LINK_STATE_U0 = 0x00, /* in HS, means ON */
// DWC3_LINK_STATE_U3 = 0x03, /* in HS, means SUSPEND */
// DWC3_LINK_STATE_SS_DIS = 0x04,
// DWC3_LINK_STATE_RX_DET = 0x05, /* in HS, means Early Suspend */

dwc3_gadget_linksts_change_interrupt LINK STATUS Change 0>0
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 0>5
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 5>3
dwc3_suspend_gadget
dwc3_gadget_interrupt RESET
dwc3_gadget_reset_interrupt
dwc3_stop_active_transfers
dwc3_clear_stall_all_ep
dwc3_gadget_interrupt CON DONE
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 3>0
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 0>5
dwc3_gadget_interrupt RESET
dwc3_gadget_reset_interrupt
dwc3_reset_gadget
dwc3_stop_active_transfers
dwc3_clear_stall_all_ep
dwc3_gadget_interrupt CON DONE
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 5>0
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 0>5
dwc3_gadget_interrupt RESET
dwc3_gadget_reset_interrupt
dwc3_reset_gadget
dwc3_stop_active_transfers
dwc3_clear_stall_all_ep
dwc3_gadget_interrupt CON DONE
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 5>0
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 0>5
dwc3_gadget_interrupt RESET
dwc3_gadget_reset_interrupt
dwc3_reset_gadget
dwc3_stop_active_transfers
dwc3_clear_stall_all_ep
dwc3_gadget_interrupt CON DONE
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 5>0
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 0>5
dwc3_gadget_interrupt RESET
dwc3_gadget_reset_interrupt
dwc3_reset_gadget
dwc3_stop_active_transfers
dwc3_clear_stall_all_ep
dwc3_gadget_interrupt CON DONE
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 5>0
enable_endpoint
dwc3_gadget_ep_enable
enable_endpoint
dwc3_gadget_ep_enable

// Ubuntu Host detect the connection
// Check partition and transfer data

dwc3_endpoint_interrupt XFERNOTREADY
dwc3_endpoint_interrupt XFERCOMPLETE
dwc3_endpoint_interrupt XFERNOTREADY
dwc3_endpoint_interrupt XFERCOMPLETE
dwc3_endpoint_interrupt XFERCOMPLETE
..
dwc3_endpoint_interrupt XFERCOMPLETE
dwc3_endpoint_interrupt XFERCOMPLETE
dwc3_endpoint_interrupt XFERCOMPLETE

// Remove the USB cable from the host

dwc3_gadget_linksts_change_interrupt LINK STATUS Change 0>5
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 5>3
dwc3_suspend_gadget
dwc3_gadget_interrupt DISCONNECT
dwc3_gadget_disconnect_interrupt
dwc3_gadget_linksts_change_interrupt LINK STATUS Change 3>4

// Disconnect UMS from Device side (D+ low)

CTRL+C - Operation aborted
unregistering UDC driver [<NULL>]
dwc3_gadget_run_stop is_on[0]
dwc3_gadget_run_stop is_on[0]
usb_gadget_udc_stop
unregistering gadget
dwc3_set_mode 2
dwc3_gadget_run
=>

• DTS : Device Tree Source
• DTB : Device Tree Blob (compiled DTS)

DTB는 IBM OpenFirmware specification에서 옴

Bootloader/U-boot에서 kernel로 low-level hardware information을 전달

DeviceTree.org : 
Device Tree is a data structure for describing hardware. Rather than hard coding every detail of a device into an operating system, many aspects of the hardware can be described in the data structure that is passed to the operating system at boot time.

Compiling

$ sudo apt-get update
$ sudo apt-get update $ sudo apt-get install device-tree-compiler


$ dtc -I dtb -O dts juno.dtb > juno.dts
$ dtc -I dts -O dtb juno.dts > juno.dtb

Denx Software Engineering wiki page

https://community.arm.com/oss-platforms/w/docs/525/device-tree