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scsi: docs: convert ufs.txt to ReST

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Link: https://lore.kernel.org/r/052d45576e342a217185e91a83793b384b1592a4.1583136624.git.mchehab+huawei@kernel.org
Acked-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Mauro Carvalho Chehab 2020-03-02 09:16:13 +01:00 committed by Martin K. Petersen
parent e92c45d272
commit b64f682240
4 changed files with 57 additions and 32 deletions
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1
Documentation/scsi/index.rst
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@ -44,5 +44,6 @@ Linux SCSI Subsystem
sym53c500_cs
sym53c8xx_2
tcm_qla2xxx
ufs
scsi_transport_srp/figures

60
Documentation/scsi/ufs.txt → Documentation/scsi/ufs.rst
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@ -1,9 +1,11 @@
.. SPDX-License-Identifier: GPL-2.0
=======================
Universal Flash Storage
=======================
Contents
--------
.. Contents
1. Overview
2. UFS Architecture Overview
@ -18,7 +20,7 @@ Contents
1. Overview
-----------
===========
Universal Flash Storage(UFS) is a storage specification for flash devices.
It is aimed to provide a universal storage interface for both
@ -28,19 +30,25 @@ 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,
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.
@ -48,16 +56,22 @@ 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
@ -65,10 +79,12 @@ UFS communication architecture consists of following layers,
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.
@ -76,20 +92,23 @@ UFS communication architecture consists of following layers,
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
@ -98,12 +117,14 @@ 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
@ -112,11 +133,13 @@ The current UFSHCD implementation supports following functionality,
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
@ -129,7 +152,7 @@ In this version of UFSHCD Query requests and power management
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
@ -138,7 +161,7 @@ request_upiu and reply_upiu respectively. Filling those UPIUs should
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;
@ -166,6 +189,7 @@ upiu-based protocol is available at:
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

2
MAINTAINERS
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@ -17140,7 +17140,7 @@ R: Alim Akhtar <alim.akhtar@samsung.com>
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

2
drivers/scsi/ufs/Kconfig
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@ -46,7 +46,7 @@ config SCSI_UFSHCD
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.