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Date: Wed, 29 Feb 2012 12:11:54 +0530 From: Santosh Y <santoshsy@...il.com> To: James.Bottomley@...senpartnership.com Cc: linux-scsi@...r.kernel.org, patches@...aro.org, linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org, arnd.bergmann@...aro.org, saugata.das@...aro.org, dsaxena@...aro.org, stephen.doel@...aro.org, venkat@...aro.org, ilho215.lee@...sung.com, nala.la@...sung.com, girish.shivananjappa@...aro.org, vishak.g@...sung.com, k.rajesh@...sung.com, yejin.moon@...sung.com, sreekumar.c@...sung.com, vinholikatti@...il.com, linkinjeon@...il.com, michaelc@...wisc.edu, Santosh Yaraganavi <santoshsy@...il.com> Subject: [PATCH v3 5/5] Documentation: UFS Host Controller Driver From: Santosh Yaraganavi <santoshsy@...il.com> The document provides Universal Flash Storage(UFS) and UFS host controller driver overview. Signed-off-by: Santosh Yaraganavi <santoshsy@...il.com> Reviewed-by: Vishak G <vishak.g@...sung.com> Reviewed-by: Namjae Jeon <linkinjeon@...il.com> --- Documentation/scsi/00-INDEX | 2 + Documentation/scsi/ufs.txt | 133 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 135 insertions(+), 0 deletions(-) create mode 100644 Documentation/scsi/ufs.txt diff --git a/Documentation/scsi/00-INDEX b/Documentation/scsi/00-INDEX index b48ded5..b7dd650 100644 --- a/Documentation/scsi/00-INDEX +++ b/Documentation/scsi/00-INDEX @@ -94,3 +94,5 @@ sym53c8xx_2.txt - info on second generation driver for sym53c8xx based adapters tmscsim.txt - info on driver for AM53c974 based adapters +ufs.txt + - info on Universal Flash Storage(UFS) and UFS host controller driver. diff --git a/Documentation/scsi/ufs.txt b/Documentation/scsi/ufs.txt new file mode 100644 index 0000000..41a6164 --- /dev/null +++ b/Documentation/scsi/ufs.txt @@ -0,0 +1,133 @@ + 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 + + +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 +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 +physical layer and MIPI Unipro as the link layer. + +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) + 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 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 + UFS which are meant for command queue control. + * 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 + requests which are used to modify and retrieve configuration + 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. + * UTP_CMD_SAP: Command service access point is exposed to UFS command + 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 +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 + controller. Also, the module decodes, responses received from UFS + host controller in the form of UPIUs and intimates the SCSI Midlayer + 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 + issues by 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 +functionality are not implemented. + +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 -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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