scsi: docs: convert ufs.txt to ReST

   sym53c500_cs

   sym53c8xx_2

   tcm_qla2xxx

   ufs

   scsi_transport_srp/figures

.. SPDX-License-Identifier: GPL-2.0

=======================

Universal Flash Storage

=======================

Contents

--------

.. Contents

   1. Overview

   2. UFS Architecture Overview

1. Overview

-----------

===========

Universal Flash Storage(UFS) is a storage specification for flash devices.

It is aimed to provide a universal storage interface for both

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,

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)

   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)

   - 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

  * 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

  * 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

     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.

    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

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

  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

functionality are not implemented.

4. BSG Support

------------------

==============

This transport driver supports exchanging UFS protocol information units

(UPIUs) with a UFS device. Typically, user space will allocate

be done in accordance with JEDEC spec UFS2.1 paragraph 10.7.

*Caveat emptor*: The driver makes no further input validations and sends the

UPIU to the device as it is.  Open the bsg device in /dev/ufs-bsg and

send SG_IO with the applicable sg_io_v4:

send SG_IO with the applicable sg_io_v4::

	io_hdr_v4.guard = 'Q';

	io_hdr_v4.protocol = BSG_PROTOCOL_SCSI;

For more detailed information about the tool and its supported

features, please see the tool's README.

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

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

R:	Avri Altman <avri.altman@wdc.com>

L:	linux-scsi@vger.kernel.org

S:	Supported

F:	Documentation/scsi/ufs.txt

F:	Documentation/scsi/ufs.rst

F:	drivers/scsi/ufs/

UNIVERSAL FLASH STORAGE HOST CONTROLLER DRIVER DWC HOOKS

	  The module will be called ufshcd.

	  To compile this driver as a module, choose M here and read

	  <file:Documentation/scsi/ufs.txt>.

	  <file:Documentation/scsi/ufs.rst>.

	  However, do not compile this as a module if your root file system

	  (the one containing the directory /) is located on a UFS device.