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1.. SPDX-License-Identifier: GPL-2.0
2
3=======================
4Universal Flash Storage
5=======================
6
7
8.. Contents
9
10 1. Overview
11 2. UFS Architecture Overview
12 2.1 Application Layer
13 2.2 UFS Transport Protocol (UTP) layer
14 2.3 UFS Interconnect (UIC) Layer
15 3. UFSHCD Overview
16 3.1 UFS controller initialization
17 3.2 UTP Transfer requests
18 3.3 UFS error handling
19 3.4 SCSI Error handling
20 4. BSG Support
21 5. UFS Reference Clock Frequency configuration
22
23
241. Overview
25===========
26
27Universal Flash Storage (UFS) is a storage specification for flash devices.
28It aims to provide a universal storage interface for both
29embedded and removable flash memory-based storage in mobile
30devices such as smart phones and tablet computers. The specification
31is defined by JEDEC Solid State Technology Association. UFS is based
32on the MIPI M-PHY physical layer standard. UFS uses MIPI M-PHY as the
33physical layer and MIPI Unipro as the link layer.
34
35The main goals of UFS are to provide:
36
37 * Optimized performance:
38
39 For UFS version 1.0 and 1.1 the target performance is as follows:
40
41 - Support for Gear1 is mandatory (rate A: 1248Mbps, rate B: 1457.6Mbps)
42 - Support for Gear2 is optional (rate A: 2496Mbps, rate B: 2915.2Mbps)
43
44 Future version of the standard,
45
46 - Gear3 (rate A: 4992Mbps, rate B: 5830.4Mbps)
47
48 * Low power consumption
49 * High random IOPs and low latency
50
51
522. UFS Architecture Overview
53============================
54
55UFS has a layered communication architecture which is based on SCSI
56SAM-5 architectural model.
57
58UFS communication architecture consists of the following layers.
59
602.1 Application Layer
61---------------------
62
63 The Application layer is composed of the UFS command set layer (UCS),
64 Task Manager and Device manager. The UFS interface is designed to be
65 protocol agnostic, however SCSI has been selected as a baseline
66 protocol for versions 1.0 and 1.1 of the UFS protocol layer.
67
68 UFS supports a subset of SCSI commands defined by SPC-4 and SBC-3.
69
70 * UCS:
71 It handles SCSI commands supported by UFS specification.
72 * Task manager:
73 It handles task management functions defined by the
74 UFS which are meant for command queue control.
75 * Device manager:
76 It handles device level operations and device
77 configuration operations. Device level operations mainly involve
78 device power management operations and commands to Interconnect
79 layers. Device level configurations involve handling of query
80 requests which are used to modify and retrieve configuration
81 information of the device.
82
832.2 UFS Transport Protocol (UTP) layer
84--------------------------------------
85
86 The UTP layer provides services for
87 the higher layers through Service Access Points. UTP defines 3
88 service access points for higher layers.
89
90 * UDM_SAP: Device manager service access point is exposed to device
91 manager for device level operations. These device level operations
92 are done through query requests.
93 * UTP_CMD_SAP: Command service access point is exposed to UFS command
94 set layer (UCS) to transport commands.
95 * UTP_TM_SAP: Task management service access point is exposed to task
96 manager to transport task management functions.
97
98 UTP transports messages through UFS protocol information unit (UPIU).
99
1002.3 UFS Interconnect (UIC) Layer
101--------------------------------
102
103 UIC is the lowest layer of the UFS layered architecture. It handles
104 the connection between UFS host and UFS device. UIC consists of
105 MIPI UniPro and MIPI M-PHY. UIC provides 2 service access points
106 to upper layer:
107
108 * UIC_SAP: To transport UPIU between UFS host and UFS device.
109 * UIO_SAP: To issue commands to Unipro layers.
110
111
1123. UFSHCD Overview
113==================
114
115The UFS host controller driver is based on the Linux SCSI Framework.
116UFSHCD is a low-level device driver which acts as an interface between
117the SCSI Midlayer and PCIe-based UFS host controllers.
118
119The current UFSHCD implementation supports the following functionality:
120
1213.1 UFS controller initialization
122---------------------------------
123
124 The initialization module brings the UFS host controller to active state
125 and prepares the controller to transfer commands/responses between
126 UFSHCD and UFS device.
127
1283.2 UTP Transfer requests
129-------------------------
130
131 Transfer request handling module of UFSHCD receives SCSI commands
132 from the SCSI Midlayer, forms UPIUs and issues the UPIUs to the UFS Host
133 controller. Also, the module decodes responses received from the UFS
134 host controller in the form of UPIUs and intimates the SCSI Midlayer
135 of the status of the command.
136
1373.3 UFS error handling
138----------------------
139
140 Error handling module handles Host controller fatal errors,
141 Device fatal errors and UIC interconnect layer-related errors.
142
1433.4 SCSI Error handling
144-----------------------
145
146 This is done through UFSHCD SCSI error handling routines registered
147 with the SCSI Midlayer. Examples of some of the error handling commands
148 issues by the SCSI Midlayer are Abort task, LUN reset and host reset.
149 UFSHCD Routines to perform these tasks are registered with
150 SCSI Midlayer through .eh_abort_handler, .eh_device_reset_handler and
151 .eh_host_reset_handler.
152
153In this version of UFSHCD, Query requests and power management
154functionality are not implemented.
155
1564. BSG Support
157==============
158
159This transport driver supports exchanging UFS protocol information units
160(UPIUs) with a UFS device. Typically, user space will allocate
161struct ufs_bsg_request and struct ufs_bsg_reply (see ufs_bsg.h) as
162request_upiu and reply_upiu respectively. Filling those UPIUs should
163be done in accordance with JEDEC spec UFS2.1 paragraph 10.7.
164*Caveat emptor*: The driver makes no further input validations and sends the
165UPIU to the device as it is. Open the bsg device in /dev/ufs-bsg and
166send SG_IO with the applicable sg_io_v4::
167
168 io_hdr_v4.guard = 'Q';
169 io_hdr_v4.protocol = BSG_PROTOCOL_SCSI;
170 io_hdr_v4.subprotocol = BSG_SUB_PROTOCOL_SCSI_TRANSPORT;
171 io_hdr_v4.response = (__u64)reply_upiu;
172 io_hdr_v4.max_response_len = reply_len;
173 io_hdr_v4.request_len = request_len;
174 io_hdr_v4.request = (__u64)request_upiu;
175 if (dir == SG_DXFER_TO_DEV) {
176 io_hdr_v4.dout_xfer_len = (uint32_t)byte_cnt;
177 io_hdr_v4.dout_xferp = (uintptr_t)(__u64)buff;
178 } else {
179 io_hdr_v4.din_xfer_len = (uint32_t)byte_cnt;
180 io_hdr_v4.din_xferp = (uintptr_t)(__u64)buff;
181 }
182
183If you wish to read or write a descriptor, use the appropriate xferp of
184sg_io_v4.
185
186The userspace tool that interacts with the ufs-bsg endpoint and uses its
187UPIU-based protocol is available at:
188
189 https://github.com/westerndigitalcorporation/ufs-tool
190
191For more detailed information about the tool and its supported
192features, please see the tool's README.
193
194UFS specifications can be found at:
195
196- UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf
197- UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf
198
1995. UFS Reference Clock Frequency configuration
200==============================================
201
202Devicetree can define a clock named "ref_clk" under the UFS controller node
203to specify the intended reference clock frequency for the UFS storage
204parts. ACPI-based system can specify the frequency using ACPI
205Device-Specific Data property named "ref-clk-freq". In both ways the value
206is interpreted as frequency in Hz and must match one of the values given in
207the UFS specification. UFS subsystem will attempt to read the value when
208executing common controller initialization. If the value is available, UFS
209subsystem will ensure the bRefClkFreq attribute of the UFS storage device is
210set accordingly and will modify it if there is a mismatch.
1.. SPDX-License-Identifier: GPL-2.0
2
3=======================
4Universal Flash Storage
5=======================
6
7
8.. Contents
9
10 1. Overview
11 2. UFS Architecture Overview
12 2.1 Application Layer
13 2.2 UFS Transport Protocol(UTP) layer
14 2.3 UFS Interconnect(UIC) Layer
15 3. UFSHCD Overview
16 3.1 UFS controller initialization
17 3.2 UTP Transfer requests
18 3.3 UFS error handling
19 3.4 SCSI Error handling
20
21
221. Overview
23===========
24
25Universal Flash Storage(UFS) is a storage specification for flash devices.
26It is aimed to provide a universal storage interface for both
27embedded and removable flash memory based storage in mobile
28devices such as smart phones and tablet computers. The specification
29is defined by JEDEC Solid State Technology Association. UFS is based
30on MIPI M-PHY physical layer standard. UFS uses MIPI M-PHY as the
31physical layer and MIPI Unipro as the link layer.
32
33The main goals of UFS is to provide:
34
35 * Optimized performance:
36
37 For UFS version 1.0 and 1.1 the target performance is as follows:
38
39 - Support for Gear1 is mandatory (rate A: 1248Mbps, rate B: 1457.6Mbps)
40 - Support for Gear2 is optional (rate A: 2496Mbps, rate B: 2915.2Mbps)
41
42 Future version of the standard,
43
44 - Gear3 (rate A: 4992Mbps, rate B: 5830.4Mbps)
45
46 * Low power consumption
47 * High random IOPs and low latency
48
49
502. UFS Architecture Overview
51============================
52
53UFS has a layered communication architecture which is based on SCSI
54SAM-5 architectural model.
55
56UFS communication architecture consists of following layers,
57
582.1 Application Layer
59---------------------
60
61 The Application layer is composed of UFS command set layer(UCS),
62 Task Manager and Device manager. The UFS interface is designed to be
63 protocol agnostic, however SCSI has been selected as a baseline
64 protocol for versions 1.0 and 1.1 of UFS protocol layer.
65
66 UFS supports subset of SCSI commands defined by SPC-4 and SBC-3.
67
68 * UCS:
69 It handles SCSI commands supported by UFS specification.
70 * Task manager:
71 It handles task management functions defined by the
72 UFS which are meant for command queue control.
73 * Device manager:
74 It handles device level operations and device
75 configuration operations. Device level operations mainly involve
76 device power management operations and commands to Interconnect
77 layers. Device level configurations involve handling of query
78 requests which are used to modify and retrieve configuration
79 information of the device.
80
812.2 UFS Transport Protocol(UTP) layer
82-------------------------------------
83
84 UTP layer provides services for
85 the higher layers through Service Access Points. UTP defines 3
86 service access points for higher layers.
87
88 * UDM_SAP: Device manager service access point is exposed to device
89 manager for device level operations. These device level operations
90 are done through query requests.
91 * UTP_CMD_SAP: Command service access point is exposed to UFS command
92 set layer(UCS) to transport commands.
93 * UTP_TM_SAP: Task management service access point is exposed to task
94 manager to transport task management functions.
95
96 UTP transports messages through UFS protocol information unit(UPIU).
97
982.3 UFS Interconnect(UIC) Layer
99-------------------------------
100
101 UIC is the lowest layer of UFS layered architecture. It handles
102 connection between UFS host and UFS device. UIC consists of
103 MIPI UniPro and MIPI M-PHY. UIC provides 2 service access points
104 to upper layer,
105
106 * UIC_SAP: To transport UPIU between UFS host and UFS device.
107 * UIO_SAP: To issue commands to Unipro layers.
108
109
1103. UFSHCD Overview
111==================
112
113The UFS host controller driver is based on Linux SCSI Framework.
114UFSHCD is a low level device driver which acts as an interface between
115SCSI Midlayer and PCIe based UFS host controllers.
116
117The current UFSHCD implementation supports following functionality,
118
1193.1 UFS controller initialization
120---------------------------------
121
122 The initialization module brings UFS host controller to active state
123 and prepares the controller to transfer commands/response between
124 UFSHCD and UFS device.
125
1263.2 UTP Transfer requests
127-------------------------
128
129 Transfer request handling module of UFSHCD receives SCSI commands
130 from SCSI Midlayer, forms UPIUs and issues the UPIUs to UFS Host
131 controller. Also, the module decodes, responses received from UFS
132 host controller in the form of UPIUs and intimates the SCSI Midlayer
133 of the status of the command.
134
1353.3 UFS error handling
136----------------------
137
138 Error handling module handles Host controller fatal errors,
139 Device fatal errors and UIC interconnect layer related errors.
140
1413.4 SCSI Error handling
142-----------------------
143
144 This is done through UFSHCD SCSI error handling routines registered
145 with SCSI Midlayer. Examples of some of the error handling commands
146 issues by SCSI Midlayer are Abort task, Lun reset and host reset.
147 UFSHCD Routines to perform these tasks are registered with
148 SCSI Midlayer through .eh_abort_handler, .eh_device_reset_handler and
149 .eh_host_reset_handler.
150
151In this version of UFSHCD Query requests and power management
152functionality are not implemented.
153
1544. BSG Support
155==============
156
157This transport driver supports exchanging UFS protocol information units
158(UPIUs) with a UFS device. Typically, user space will allocate
159struct ufs_bsg_request and struct ufs_bsg_reply (see ufs_bsg.h) as
160request_upiu and reply_upiu respectively. Filling those UPIUs should
161be done in accordance with JEDEC spec UFS2.1 paragraph 10.7.
162*Caveat emptor*: The driver makes no further input validations and sends the
163UPIU to the device as it is. Open the bsg device in /dev/ufs-bsg and
164send SG_IO with the applicable sg_io_v4::
165
166 io_hdr_v4.guard = 'Q';
167 io_hdr_v4.protocol = BSG_PROTOCOL_SCSI;
168 io_hdr_v4.subprotocol = BSG_SUB_PROTOCOL_SCSI_TRANSPORT;
169 io_hdr_v4.response = (__u64)reply_upiu;
170 io_hdr_v4.max_response_len = reply_len;
171 io_hdr_v4.request_len = request_len;
172 io_hdr_v4.request = (__u64)request_upiu;
173 if (dir == SG_DXFER_TO_DEV) {
174 io_hdr_v4.dout_xfer_len = (uint32_t)byte_cnt;
175 io_hdr_v4.dout_xferp = (uintptr_t)(__u64)buff;
176 } else {
177 io_hdr_v4.din_xfer_len = (uint32_t)byte_cnt;
178 io_hdr_v4.din_xferp = (uintptr_t)(__u64)buff;
179 }
180
181If you wish to read or write a descriptor, use the appropriate xferp of
182sg_io_v4.
183
184The userspace tool that interacts with the ufs-bsg endpoint and uses its
185upiu-based protocol is available at:
186
187 https://github.com/westerndigitalcorporation/ufs-tool
188
189For more detailed information about the tool and its supported
190features, please see the tool's README.
191
192UFS Specifications can be found at:
193
194- UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf
195- UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf