Documentation/scsi/ufs.rst

1 .. SPDX-License-Identifier: GPL-2.0
11    2. UFS Architecture Overview
13      2.2 UFS Transport Protocol(UTP) layer
14      2.3 UFS Interconnect(UIC) Layer
16      3.1 UFS controller initialization
18      3.3 UFS error handling
25 Universal Flash Storage(UFS) is a storage specification for flash devices.
29 is defined by JEDEC Solid State Technology Association. UFS is based
30 on MIPI M-PHY physical layer standard. UFS uses MIPI M-PHY as the
33 The main goals of UFS is to provide:
37    For UFS version 1.0 and 1.1 the target performance is as follows:
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)
44    - Gear3 (rate A: 4992Mbps, rate B: 5830.4Mbps)
50 2. UFS Architecture Overview
53 UFS has a layered communication architecture which is based on SCSI
54 SAM-5 architectural model.
56 UFS communication architecture consists of following layers,
59 ---------------------
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
64   protocol for versions 1.0 and 1.1 of UFS protocol  layer.
66   UFS supports subset of SCSI commands defined by SPC-4 and SBC-3.
69      It handles SCSI commands supported by UFS specification.
72      UFS which are meant for command queue control.
81 2.2 UFS Transport Protocol(UTP) layer
82 -------------------------------------
91   * UTP_CMD_SAP: Command service access point is exposed to UFS command
96   UTP transports messages through UFS protocol information unit(UPIU).
98 2.3 UFS Interconnect(UIC) Layer
99 -------------------------------
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
106   * UIC_SAP: To transport UPIU between UFS host and UFS device.
113 The UFS host controller driver is based on Linux SCSI Framework.
115 SCSI Midlayer and PCIe based UFS host controllers.
119 3.1 UFS controller initialization
120 ---------------------------------
122   The initialization module brings UFS host controller to active state
124   UFSHCD and UFS device.
127 -------------------------
130   from SCSI Midlayer, forms UPIUs and issues the UPIUs to UFS Host
131   controller. Also, the module decodes, responses received from UFS
135 3.3 UFS error handling
136 ----------------------
142 -----------------------
157 This transport driver supports exchanging UFS protocol information units
158 (UPIUs) with a UFS device. Typically, user space will allocate
163 UPIU to the device as it is.  Open the bsg device in /dev/ufs-bsg and
184 The userspace tool that interacts with the ufs-bsg endpoint and uses its
185 upiu-based protocol is available at:
187 	https://github.com/westerndigitalcorporation/ufs-tool
192 UFS Specifications can be found at:
194 - UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf
195 - UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf