Documentation/scsi/ufs.rst

Source file repositories/reference/linux-study-clean/Documentation/scsi/ufs.rst

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Linux kernel
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Documentation/scsi/ufs.rst
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.rst
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Support Tooling And Documentation
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Documentation
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Support Tooling And Documentation: documentation
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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.. SPDX-License-Identifier: GPL-2.0

=======================
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
   4. BSG Support
   5. UFS Reference Clock Frequency configuration


1. Overview
===========

Universal Flash Storage (UFS) is a storage specification for flash devices.
It aims 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 the 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 are 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 the following layers.

2.1 Application Layer
---------------------

  The Application layer is composed of the 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 the UFS protocol layer.

  UFS supports a subset of SCSI commands defined by SPC-4 and SBC-3.

  * UCS:

Annotation

Implementation Notes