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Diffstat (limited to 'Documentation/scsi/ufs.rst')
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1 files changed, 50 insertions, 35 deletions
diff --git a/Documentation/scsi/ufs.rst b/Documentation/scsi/ufs.rst index a920c0a5a1f6..885b1a736e3f 100644 --- a/Documentation/scsi/ufs.rst +++ b/Documentation/scsi/ufs.rst @@ -10,27 +10,29 @@ Universal Flash Storage 1. Overview 2. UFS Architecture Overview 2.1 Application Layer - 2.2 UFS Transport Protocol(UTP) layer - 2.3 UFS Interconnect(UIC) 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 is aimed to provide a universal storage interface for both -embedded and removable flash memory based storage in mobile +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 MIPI M-PHY physical layer standard. UFS uses MIPI M-PHY as the +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 is to provide: +The main goals of UFS are to provide: * Optimized performance: @@ -53,17 +55,17 @@ The main goals of UFS is to provide: UFS has a layered communication architecture which is based on SCSI SAM-5 architectural model. -UFS communication architecture consists of following layers, +UFS communication architecture consists of the following layers. 2.1 Application Layer --------------------- - The Application layer is composed of UFS command set layer(UCS), + 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 UFS protocol layer. + protocol for versions 1.0 and 1.1 of the UFS protocol layer. - UFS supports subset of SCSI commands defined by SPC-4 and SBC-3. + UFS supports a subset of SCSI commands defined by SPC-4 and SBC-3. * UCS: It handles SCSI commands supported by UFS specification. @@ -78,10 +80,10 @@ UFS communication architecture consists of following layers, requests which are used to modify and retrieve configuration information of the device. -2.2 UFS Transport Protocol(UTP) layer -------------------------------------- +2.2 UFS Transport Protocol (UTP) layer +-------------------------------------- - UTP layer provides services for + The UTP layer provides services for the higher layers through Service Access Points. UTP defines 3 service access points for higher layers. @@ -89,19 +91,19 @@ UFS communication architecture consists of following layers, manager for device level operations. These device level operations are done through query requests. * UTP_CMD_SAP: Command service access point is exposed to UFS command - set layer(UCS) to transport commands. + 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). + UTP transports messages through UFS protocol information unit (UPIU). -2.3 UFS Interconnect(UIC) Layer -------------------------------- +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 + UIC is the lowest layer of the UFS layered architecture. It handles + the 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, + to upper layer: * UIC_SAP: To transport UPIU between UFS host and UFS device. * UIO_SAP: To issue commands to Unipro layers. @@ -110,25 +112,25 @@ UFS communication architecture consists of following 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 -SCSI Midlayer and PCIe based UFS host controllers. +The UFS host controller driver is based on the Linux SCSI Framework. +UFSHCD is a low-level device driver which acts as an interface between +the SCSI Midlayer and PCIe-based UFS host controllers. -The current UFSHCD implementation supports following functionality, +The current UFSHCD implementation supports the 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 + The initialization module brings the UFS host controller to active state + and prepares the controller to transfer commands/responses 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 - controller. Also, the module decodes, responses received from UFS + from the SCSI Midlayer, forms UPIUs and issues the UPIUs to the UFS Host + controller. Also, the module decodes responses received from the UFS host controller in the form of UPIUs and intimates the SCSI Midlayer of the status of the command. @@ -136,19 +138,19 @@ The current UFSHCD implementation supports following functionality, ---------------------- Error handling module handles Host controller fatal errors, - Device fatal errors and UIC interconnect layer related 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 - issues by SCSI Midlayer are Abort task, Lun reset and host reset. + with the SCSI Midlayer. Examples of some of the error handling commands + issues by the SCSI Midlayer are Abort task, LUN reset and host reset. UFSHCD Routines to perform these tasks are registered with SCSI Midlayer through .eh_abort_handler, .eh_device_reset_handler and .eh_host_reset_handler. -In this version of UFSHCD Query requests and power management +In this version of UFSHCD, Query requests and power management functionality are not implemented. 4. BSG Support @@ -182,14 +184,27 @@ If you wish to read or write a descriptor, use the appropriate xferp of sg_io_v4. The userspace tool that interacts with the ufs-bsg endpoint and uses its -upiu-based protocol is available at: +UPIU-based protocol is available at: https://github.com/westerndigitalcorporation/ufs-tool For more detailed information about the tool and its supported features, please see the tool's README. -UFS Specifications can be found at: +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 + +5. UFS Reference Clock Frequency configuration +============================================== + +Devicetree can define a clock named "ref_clk" under the UFS controller node +to specify the intended reference clock frequency for the UFS storage +parts. ACPI-based system can specify the frequency using ACPI +Device-Specific Data property named "ref-clk-freq". In both ways the value +is interpreted as frequency in Hz and must match one of the values given in +the UFS specification. UFS subsystem will attempt to read the value when +executing common controller initialization. If the value is available, UFS +subsytem will ensure the bRefClkFreq attribute of the UFS storage device is +set accordingly and will modify it if there is a mismatch. |