[mirror_ubuntu-bionic-kernel.git] / Documentation / scsi / ufs.txt

                       Universal Flash Storage
                       =======================


Contents
--------

1. Overview
2. UFS Architecture Overview
  2.1 Application Layer
  2.2 UFS Transport Protocol(UTP) layer
  2.3 UFS Interconnect(UIC) Layer
3. UFSHCD Overview
  3.1 UFS controller initialization
  3.2 UTP Transfer requests
  3.3 UFS error handling
  3.4 SCSI Error handling


1. Overview
-----------

Universal Flash Storage(UFS) is a storage specification for flash devices.
It is aimed to provide a universal storage interface for both
embedded and removable flash memory based storage in mobile
devices such as smart phones and tablet computers. The specification
is defined by JEDEC Solid State Technology Association. UFS is based
on MIPI M-PHY physical layer standard. UFS uses MIPI M-PHY as the
physical layer and MIPI Unipro as the link layer.

The main goals of UFS is to provide,
 * Optimized performance:
   For UFS version 1.0 and 1.1 the target performance is as follows,
   Support for Gear1 is mandatory (rate A: 1248Mbps, rate B: 1457.6Mbps)
   Support for Gear2 is optional (rate A: 2496Mbps, rate B: 2915.2Mbps)
   Future version of the standard,
   Gear3 (rate A: 4992Mbps, rate B: 5830.4Mbps)
 * Low power consumption
 * High random IOPs and low latency


2. UFS Architecture Overview
----------------------------

UFS has a layered communication architecture which is based on SCSI
SAM-5 architectural model.

UFS communication architecture consists of following layers,

2.1 Application Layer

  The Application layer is composed of UFS command set layer(UCS),
  Task Manager and Device manager. The UFS interface is designed to be
  protocol agnostic, however SCSI has been selected as a baseline
  protocol for versions 1.0 and 1.1 of UFS protocol  layer.
  UFS supports subset of SCSI commands defined by SPC-4 and SBC-3.
  * UCS: It handles SCSI commands supported by UFS specification.
  * Task manager: It handles task management functions defined by the
     UFS which are meant for command queue control.
  * Device manager: It handles device level operations and device
     configuration operations. Device level operations mainly involve
     device power management operations and commands to Interconnect
     layers. Device level configurations involve handling of query
     requests which are used to modify and retrieve configuration
     information of the device.

2.2 UFS Transport Protocol(UTP) layer

  UTP layer provides services for
  the higher layers through Service Access Points. UTP defines 3
  service access points for higher layers.
  * UDM_SAP: Device manager service access point is exposed to device
    manager for device level operations. These device level operations
    are done through query requests.
  * UTP_CMD_SAP: Command service access point is exposed to UFS command
    set layer(UCS) to transport commands.
  * UTP_TM_SAP: Task management service access point is exposed to task
    manager to transport task management functions.
  UTP transports messages through UFS protocol information unit(UPIU).

2.3 UFS Interconnect(UIC) Layer

  UIC is the lowest layer of UFS layered architecture. It handles
  connection between UFS host and UFS device. UIC consists of
  MIPI UniPro and MIPI M-PHY. UIC provides 2 service access points
  to upper layer,
  * UIC_SAP: To transport UPIU between UFS host and UFS device.
  * UIO_SAP: To issue commands to Unipro layers.


3. UFSHCD Overview
------------------

The UFS host controller driver is based on Linux SCSI Framework.
UFSHCD is a low level device driver which acts as an interface between
SCSI Midlayer and PCIe based UFS host controllers.

The current UFSHCD implementation supports following functionality,

3.1 UFS controller initialization

  The initialization module brings UFS host controller to active state
  and prepares the controller to transfer commands/response between
  UFSHCD and UFS device.

3.2 UTP Transfer requests

  Transfer request handling module of UFSHCD receives SCSI commands
  from SCSI Midlayer, forms UPIUs and issues the UPIUs to UFS Host
  controller. Also, the module decodes, responses received from UFS
  host controller in the form of UPIUs and intimates the SCSI Midlayer
  of the status of the command.

3.3 UFS error handling

  Error handling module handles Host controller fatal errors,
  Device fatal errors and UIC interconnect layer related errors.

3.4 SCSI Error handling

  This is done through UFSHCD SCSI error handling routines registered
  with SCSI Midlayer. Examples of some of the error handling commands
  issues by SCSI Midlayer are Abort task, Lun reset and host reset.
  UFSHCD Routines to perform these tasks are registered with
  SCSI Midlayer through .eh_abort_handler, .eh_device_reset_handler and
  .eh_host_reset_handler.

In this version of UFSHCD Query requests and power management
functionality are not implemented.

UFS Specifications can be found at,
UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf
UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf
Commit	Line	Data
7a3e97b0 SY	1	Universal Flash Storage
	2	=======================
	3
	4
	5	Contents
	6	--------
	7
	8	1. Overview
	9	2. UFS Architecture Overview
	10	2.1 Application Layer
	11	2.2 UFS Transport Protocol(UTP) layer
	12	2.3 UFS Interconnect(UIC) Layer
	13	3. UFSHCD Overview
	14	3.1 UFS controller initialization
	15	3.2 UTP Transfer requests
	16	3.3 UFS error handling
	17	3.4 SCSI Error handling
	18
	19
	20	1. Overview
	21	-----------
	22
	23	Universal Flash Storage(UFS) is a storage specification for flash devices.
	24	It is aimed to provide a universal storage interface for both
	25	embedded and removable flash memory based storage in mobile
	26	devices such as smart phones and tablet computers. The specification
	27	is defined by JEDEC Solid State Technology Association. UFS is based
	28	on MIPI M-PHY physical layer standard. UFS uses MIPI M-PHY as the
	29	physical layer and MIPI Unipro as the link layer.
	30
	31	The main goals of UFS is to provide,
	32	* Optimized performance:
	33	For UFS version 1.0 and 1.1 the target performance is as follows,
	34	Support for Gear1 is mandatory (rate A: 1248Mbps, rate B: 1457.6Mbps)
	35	Support for Gear2 is optional (rate A: 2496Mbps, rate B: 2915.2Mbps)
	36	Future version of the standard,
	37	Gear3 (rate A: 4992Mbps, rate B: 5830.4Mbps)
	38	* Low power consumption
	39	* High random IOPs and low latency
	40
	41
	42	2. UFS Architecture Overview
	43	----------------------------
	44
	45	UFS has a layered communication architecture which is based on SCSI
	46	SAM-5 architectural model.
	47
	48	UFS communication architecture consists of following layers,
	49
	50	2.1 Application Layer
	51
	52	The Application layer is composed of UFS command set layer(UCS),
	53	Task Manager and Device manager. The UFS interface is designed to be
	54	protocol agnostic, however SCSI has been selected as a baseline
	55	protocol for versions 1.0 and 1.1 of UFS protocol layer.
	56	UFS supports subset of SCSI commands defined by SPC-4 and SBC-3.
	57	* UCS: It handles SCSI commands supported by UFS specification.
	58	* Task manager: It handles task management functions defined by the
	59	UFS which are meant for command queue control.
	60	* Device manager: It handles device level operations and device
	61	configuration operations. Device level operations mainly involve
	62	device power management operations and commands to Interconnect
	63	layers. Device level configurations involve handling of query
	64	requests which are used to modify and retrieve configuration
65	information of the device.
66
67	2.2 UFS Transport Protocol(UTP) layer
68
69	UTP layer provides services for
70	the higher layers through Service Access Points. UTP defines 3
71	service access points for higher layers.
72	* UDM_SAP: Device manager service access point is exposed to device
73	manager for device level operations. These device level operations
74	are done through query requests.
75	* UTP_CMD_SAP: Command service access point is exposed to UFS command
76	set layer(UCS) to transport commands.
77	* UTP_TM_SAP: Task management service access point is exposed to task
78	manager to transport task management functions.
79	UTP transports messages through UFS protocol information unit(UPIU).
80
81	2.3 UFS Interconnect(UIC) Layer
82
83	UIC is the lowest layer of UFS layered architecture. It handles
84	connection between UFS host and UFS device. UIC consists of
85	MIPI UniPro and MIPI M-PHY. UIC provides 2 service access points
86	to upper layer,
87	* UIC_SAP: To transport UPIU between UFS host and UFS device.
88	* UIO_SAP: To issue commands to Unipro layers.
89
90
91	3. UFSHCD Overview
92	------------------
93
94	The UFS host controller driver is based on Linux SCSI Framework.
95	UFSHCD is a low level device driver which acts as an interface between
96	SCSI Midlayer and PCIe based UFS host controllers.
97
98	The current UFSHCD implementation supports following functionality,
99
100	3.1 UFS controller initialization
101
102	The initialization module brings UFS host controller to active state
103	and prepares the controller to transfer commands/response between
104	UFSHCD and UFS device.
105
106	3.2 UTP Transfer requests
107
108	Transfer request handling module of UFSHCD receives SCSI commands
109	from SCSI Midlayer, forms UPIUs and issues the UPIUs to UFS Host
110	controller. Also, the module decodes, responses received from UFS
111	host controller in the form of UPIUs and intimates the SCSI Midlayer
112	of the status of the command.
113
114	3.3 UFS error handling
115
116	Error handling module handles Host controller fatal errors,
117	Device fatal errors and UIC interconnect layer related errors.
118
119	3.4 SCSI Error handling
120
121	This is done through UFSHCD SCSI error handling routines registered
122	with SCSI Midlayer. Examples of some of the error handling commands
123	issues by SCSI Midlayer are Abort task, Lun reset and host reset.
124	UFSHCD Routines to perform these tasks are registered with
125	SCSI Midlayer through .eh_abort_handler, .eh_device_reset_handler and
126	.eh_host_reset_handler.
127
128	In this version of UFSHCD Query requests and power management
129	functionality are not implemented.
130
131	UFS Specifications can be found at,
132	UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf
133	UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf