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authorMauro Carvalho Chehab <mchehab+huawei@kernel.org>2020-03-02 09:16:13 +0100
committerMartin K. Petersen <martin.petersen@oracle.com>2020-03-11 23:08:03 -0400
commitb64f682240453932f73d58438c928bdd319aeb8a (patch)
treed9dbd1a1744fdffbe3dfc9b0d40ee7199b29e2bb /Documentation/scsi
parente92c45d27236642b1e0deccc567f305f0fb3d2cc (diff)
scsi: docs: convert ufs.txt to ReST
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>
Diffstat (limited to 'Documentation/scsi')
-rw-r--r--Documentation/scsi/index.rst1
-rw-r--r--Documentation/scsi/ufs.rst (renamed from Documentation/scsi/ufs.txt)84
2 files changed, 55 insertions, 30 deletions
diff --git a/Documentation/scsi/index.rst b/Documentation/scsi/index.rst
index df005cb94f6b..27720d145eff 100644
--- a/Documentation/scsi/index.rst
+++ b/Documentation/scsi/index.rst
@@ -44,5 +44,6 @@ Linux SCSI Subsystem
sym53c500_cs
sym53c8xx_2
tcm_qla2xxx
+ ufs
scsi_transport_srp/figures
diff --git a/Documentation/scsi/ufs.txt b/Documentation/scsi/ufs.rst
index 81842ec3e116..a920c0a5a1f6 100644
--- a/Documentation/scsi/ufs.txt
+++ b/Documentation/scsi/ufs.rst
@@ -1,24 +1,26 @@
- Universal Flash Storage
- =======================
+.. 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
+.. 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
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