Abstract:
A system including a first controller configured to communicate with a host via a first interface; a second controller configured to communicate with a storage device via a second interface, where the second interface is different than the first interface; and a bridge module configured to allow the second controller to transfer data between the storage device and the host and to allow the second controller to access memory of the host via the first interface during the transfer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/405,444, filed on Oct. 21, 2010. The disclosure of the above application is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present disclosure relates generally to data storage systems and more particularly to a Universal Serial Bus (USB) to Serial Advanced Technology Attachment (SATA) high-speed bridge for storage devices. 
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     Referring now to  FIG. 1 , a data storage system  10  includes a storage device  12  and a host  14 . The storage device  12  includes a disk controller  16  and a disk drive  18 . The disk drive  18  may include a conventional disk drive that stores data on a magnetic medium, a solid-state disk that stores data on a semiconductor memory (e.g., a flash memory), or an optical disk drive that stores data on an optical disc. 
     The host  14  may include a laptop computer, a personal computer, or any other type of computing device. The storage device  12  may communicate with the host  14  via a Universal Serial Bus (USB) interface. Accordingly, the disk controller  16  may include a USB interface to communicate with the host  12 . The disk controller  16  may also include a Serial Advanced Technology Attachment (SATA) interface to communicate with the disk drive  18 . 
     SUMMARY 
     A system includes a first controller configured to communicate with a host via a first interface; a second controller configured to communicate with a storage device via a second interface, where the second interface is different than the first interface; and a bridge module configured to allow the second controller to transfer data between the storage device and the host and to allow the second controller to access memory of the host via the first interface during the transfer. 
     In another feature, the bridge module is configured to provide a path for the transfer between the storage device and the host, where the path includes the first controller, the bridge module, and the second controller, and where the path excludes a buffer to store the data. 
     In another feature, the bridge module is configured to allow the second controller to convert an incoming command from the host while the transfer is in progress. 
     In another feature, the bridge module is configured return to the host a status of the transfer by interpreting information received from the second controller about the transfer. 
     In another feature, the first interface is a Universal Serial Bus (USB) interface, and the second interface is a Serial Advanced Technology Attachment (SATA) interface. 
     In another feature, the bridge module is configured to convert a first command received from the host to a second command, where the first command is compliant with the first interface, and where the second command is compliant with the second interface; and to transfer the second command to the second interface. 
     In another feature, the bridge module includes a bridge interface module configured to receive a request from the second controller for a data path providing access to the memory of the host. The bridge module includes an arbitration module configured to provide, based on the request, the data path to the second controller to transfer the data between the storage device and the memory of the host. The data path excludes a buffer to store the data. The bridge interface module allows the second controller to transfer the data between the storage device and the memory of the host via the data path. 
     In still other features, a system-on-chip (SOC) includes a Universal Serial Bus (USB) controller configured to interface a storage controller of a storage device to a host via a USB interface, and a Serial Advanced Technology Attachment (SATA) controller configured to interface the storage controller to the storage device via a SATA interface. The SOC further includes a command handling module configured to convert a USB command received by the USB controller from the host to a SATA command, and to output the SATA command to the SATA controller. The SATA controller is configured to generate a request for a data path for access to a memory of the host to transfer data between the storage device and the memory of the host according to the SATA command. The data path is a path between the memory and the storage device. The SOC further includes a data handling module configured to receive the request from the SATA controller, and to provide the data path to the SATA controller to transfer the data between the storage device and the memory of the host. The SATA controller is configured to transfer the data between the storage device and the memory of the host according to the SATA command. 
     In another feature, the SOC further includes a status handling module configured to receive and interpret command completion information from the SATA controller; to generate, based on the command completion, a status of the transfer by determining whether the transfer is completed without error; and to send the status of the transfer to the host via the USB controller. 
     In still other features, a method includes communicating with a host via a first interface of a first controller; communicating with a storage device via a second interface of a second controller, where the second interface is different than the first interface; allowing the second controller to transfer data between the storage device and the host; and allowing the second controller to access memory of the host via the first interface during the transfer. 
     In another feature, the method further includes providing a path for the transfer between the storage device and the host, where the path includes the first controller and the second controller, and where the path excludes a buffer to store the data. 
     In another feature, the method further includes converting an incoming command from the host while the transfer is in progress. 
     In another feature, the method further includes returning to the host a status of the transfer by interpreting information received from the second controller about the transfer. 
     In another feature, in the method, the first interface is a Universal Serial Bus (USB) interface, and the second interface is a Serial Advanced Technology Attachment (SATA) interface. 
     In another feature, the method further includes converting a first command received from the host to a second command, where the first command is compliant with the first interface, and where the second command is compliant with the second interface; and transferring the second command to the second interface. 
     In another feature, the method further includes receiving a request from the second controller for a data path providing access to the memory of the host; providing, based on the request, the data path to the second controller to transfer the data between the storage device and the memory of the host, where the data path excludes a buffer to store the data; and allowing the second controller to transfer the data between the storage device and the memory of the host via the data path. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of a data storage system according to the prior art; 
         FIG. 2  is a functional block diagram of a disk controller that uses a buffer when transferring data between a host and a disk drive during read/write operations; 
         FIG. 3  is a functional block diagram of a disk controller that transfers data directly between a host and a disk drive during read/write operations without using a buffer; 
         FIG. 4  depicts data flow between a host and a disk drive when the host issues a Universal Serial Bus (USB) Bulk-only Transport (BOT) command; 
         FIG. 5  depicts data flow between a host and a disk drive when the host issues a USB Attached SCSI (UAS) command; and 
         FIGS. 6A and 6B  are flowcharts of methods for High-Speed bridge operations from command handling, data handling, status handling, and error handling perspectives. 
     
    
    
     DESCRIPTION 
     Referring now to  FIG. 2 , an example of a disk controller is shown. A disk controller  100  includes a processing module  102 , a bus interface module  107 , a buffer  104 , a Universal Serial Bus (USB) controller  106 , and a Serial Advanced Technology Attachment (SATA) controller  108 . The USB controller  106  includes a USB interface module  110  that interfaces with the host  14  and a USB direct memory access (DMA) module  112  that communicates with the USB interface module  110 , the processing module  102 , and the buffer  104 . The SATA controller  108  includes a SATA interface module  114  that interfaces with the disk drive  18  and a SATA DMA module  116  that communicates with the SATA interface module  114 , the processing module  102 , and the buffer  104 . The bus interface module  107  communicates with the USB DMA module  112 , the SATA DMA module  116 , the processing module  102 , and the buffer  104 . The bus interface module  107  provides the USB DMA module  112  and the SATA DMA module  116  a DMA path to the buffer  104 . 
     When the host  14  issues a write command to write data on the disk drive  18 , the USB DMA module  112  receives the data from the host  14  via the USB interface module  110  and stores the data in the buffer  104 . The SATA DMA module  116  retrieves the data from the buffer  104  and forwards the data to the SATA interface module  114 , which writes the data to the disk drive  18 . 
     When the host  14  issues a read command to read data from the disk drive  18 , the SATA DMA module  116  receives the data from the disk drive  18  via the SATA interface module  114  and stores the data in the buffer  104 . The USB DMA module  112  retrieves the data from the buffer  104  and forwards the data to the USB interface module  110 , which outputs the data to the host  14 . 
     Buffering data during read/write operations can decrease the rate at which data is transferred between the USB interface module  110  and the SATA interface module  114 . Consequently, performance of high-speed interfaces such as USB 3.0 and SATA 3.0 can degrade despite having data transfer rates of 5 Gigabits per second (Gbps) and 6 Gbps, respectively. Moreover, buffering data during read/write operations generates many interrupts which the processing module  102  has to process and which can increase overhead and downgrade  10  performance. 
     Buffering data during read/write operations can be eliminated by using a high-speed bridge instead of using a buffer between the USB and SATA controllers. As explained below, the bridge may work, for example, with Bulk-only Transport (BOT) and USB Attached SCSI (UAS) protocols of the USB interface and Native Command Queuing (NCQ) protocol of the SATA interface. The bridge determines a command phase, a data phase, and a status phase of data transfer between the USB and SATA controllers based on the BOT and UAS protocols. The command phase includes command conversion. The data phase includes data transfer according to the command. The status phase includes returning status of the command and associated data transfer to the host. The bridge can automatically convert an incoming command from the host. The SATA DMA module can directly receive/transmit data from/to the bridge without using the buffer. After determining that a data transaction is completed, the bridge returns status automatically based on the information received from the SATA controller. The bridge thus improves throughput and optimizes  10  performance. 
     The present disclosure uses USB and SATA interfaces for example only. The teachings of the present disclosure are not limited to USB and SATA interfaces. The teachings of the present disclosure can be applied to other interfaces used to transfer data at high speed between a host and a disk drive. 
     Referring now to  FIG. 3 , a disk controller  200  includes a processing module  202 , a USB controller  204 , a bridge module  206 , a USB DMA module  222 , a bus interface module  208 , and a SATA controller  108 . The disk controller  200  can be implemented as an integrated circuit (IC) or a system-on-chip (SOC). 
     As explained below, a command handling module  220  in the bridge module  206  interrupts the processing module  202  when a USB command is received from the host  14 . The processing module  202  converts the USB command to a SATA command. When the command is a write command to write data from the host  14  to the disk drive  18 , the SATA controller  108  accesses the memory of the host  14  and transfers data from the memory of the host  14  directly to the disk drive  18 . When the command is a read command to read data from the disk drive  18 , the SATA controller  108  reads data from the disk drive and transfers data from the disk drive  18  directly to the memory of the host  14 . The bridge module  206  allows the SATA controller  108  to directly receive/transmit data from/to memory of the host  14  without using the buffer  104  (not shown). The USB controller  204  includes the USB interface module  110 , a receive FIFO  212 , and a transmit FIFO  214 . The USB interface module  110  stores the command received from the host  14  in the receive FIFO  212 . 
     The bridge module  206  includes an arbitration module  218 , a command handling module  220 , a data handling module  224 , a status handling module  228 , and an interrupt handling module  230 . The bridge module  206  does not include the buffer  104 . The command handling module  220  interrupts the processing module  202  when an incoming command is received from the host  14 . The processing module  202  converts the command received from the host  14  to a SATA command and outputs the SATA command to the SATA controller  108  via the bus interface module  208 . The SATA controller  108  is configured to transfer data according to the SATA command. After the SATA controller  108  is configured to transfer data according to the SATA command, the SATA controller  108  sends a request to the data handling module  224  for bus ownership to transfer data directly between the SATA controller  108  and the USB controller  204 . 
     Depending on the type of command (e.g., read or write command), the arbitration module  218  arbitrates bus ownership and data flow between the USB DMA module  222  and the bridge interface module  206 . The arbitration module  218  can also perform the arbitration for the command phase, data phase, and status phase automatically without software involvement. 
     During the read operation, the arbitration module  218  arbitrates bus ownership and data flow from the data handling module  224  to the transmit FIFO  214  to provide a direct data path for the SATA DMA module  116  to transfer the data read from the disk drive  18  directly to the memory of the host  14  via the USB controller  204 . 
     During the write operation, the arbitration module  218  arbitrates bus ownership and data flow from the receive FIFO  212  and the data handling module  224  to provide a direct data path for the SATA DMA module  116  to transfer the data from the memory of the host  14  directly to the disk drive  18  via the USB controller  204 . 
     When each read/write command is completed, the SATA interface module  114  provides information directly to the status handling module  228 . The status handling module  228  can interpret the information and send out status automatically without software intervention once the data phase is completed without error. 
     While only one SATA controller is shown for simplicity of illustration, a plurality of SATA controllers can be interfaced with the bus interface module  208 . For each additional SATA controller interfaced with the bus interface module  208 , the bridge module  206  can include an additional set of the data handling module  224  and the status handling module  228 . The USB DMA module  222  handles DMA for the plurality of SATA controllers and allows each SATA controller to transfer data using a corresponding set of the data handling module  224  and the status handling module  228 . 
     The data handling module  224  provides a direct data path for the SATA DMA module  116  to receive/transmit data directly from/to the memory of the host  14  without storing the data in the buffer  104 . The data handling module  224  actively transfers data in and out of the USB controller  204  according to the SATA command. The status handling module  228  also generates status information for a command when the status handling module  228  receives command completion information directly from the module SATA interface module  114  after the data transfer corresponding to the command is completed. If an error occurs at the USB controller  204 , the interrupt handling module  230  notifies the processing module  202 . 
     Referring now to  FIG. 4 , data flows  300  for a USB Bulk-only Transport (BOT) command are shown. At  302 , the host  14  issues a USB BOT command. At  304 , the USB controller  204  receives the USB BOT command. At  306 , the USB DMA module  222  or the command handling module  220  interrupts the processing module  202 . The processing module  202  converts the USB BOT command to a SATA command and sends the SATA command to the SATA controller  108 . At  308 , the SATA controller  108  receives the SATA command. The SATA controller  108  prepares to transfer data according to the SATA command. 
     At  310 , the SATA controller  108  transfers data directly from the host  14  to the disk drive  18  if the USB command is a write command. At  312 , the SATA controller  108  transfers data directly from the disk drive  18  to the host  14  if the USB command is a read command. 
     At  314 , the SATA controller  108  interrupts the processing module  202  when the data transfer is completed. At  318 , at the same time, the SATA interface module  114  sends information directly to the status handling module  228 . The status handling module  228  interprets the information and generates status without involvement of the processing module  202 . At  320 , the host  14  receives the status information. 
     Referring now to  FIG. 5 , data flows  400  for USB Attached SCSI (UAS) commands are shown. At  402 , the host  14  issues USB UAS commands (e.g., a burst of up to 32 commands at a time per one SATA port). At  404 , the USB controller  204  receives the USB UAS commands. The USB UAS commands are not merged together. At  406 , the USB DMA module  222  or the command handling module  220  interrupts the processing module  202  (e.g., up to 32 times). 
     The processing module  202  converts the USB UAS commands to SATA commands (one-to-one conversion) and sends the SATA commands to the SATA controller  108  (e.g., up to 32 at a time). At  408 , the SATA controller  108  receives the SATA commands (e.g., up to 32 at a time). The SATA controller  108  prepares to transfer data according to the SATA commands. The SATA controller  108  sets up one DMA operation for the data transfers (read or write operations) of all the SATA commands. 
     At  410 , the SATA controller  108  transfers data directly from the host  14  to the disk drive  18  if the USB commands are write commands. For example, the SATA controller  108  performs up to 32 write operations (data transfers). At  412 , the SATA controller  108  transfers data directly from the disk drive  18  to the host  14  if the USB commands are read commands. For example, the SATA controller  108  performs up to 32 read operations (data transfers). 
     At  414 , the SATA controller  108  interrupts the processing module  202  when the data transfers for the SATA commands are completed (e.g., up to 32 at a time). At  416 , the processing module  202  receives the interrupts (e.g., up to 32 at a time). At  418 , at the same time, the SATA interface module  114  sends information directly to the status handling module  228  (e.g., up to 32 at a time). The status handling module  228  interprets the information and generates status without involvement of the processing module  202 . 
     At  420 , the host  14  receives the status information (e.g., up to 32 status information at a time). 
     Referring now to  FIG. 6A , a flowchart for command handling according to the present disclosure is shown. At  502 , the command handling module  220  is idle after power up. At  504 , the command handling module  220  receives a USB read/write command from host  14 . At  508 , the command handling module  220  notifies the processing module  202 , and the processing module  202  converts the received USB command to a SATA command. At  510 , the processing module  202  initiates a SATA read/write operation. At  512 , data is transferred directly between the high-speed bridge and the SATA controller  108 . During the direct data transfer between the high-speed bridge and the SATA controller  108 , if the command handling module  220  receives a next command, the command handling module  220  notifies the processing module  202 , which processes the next command in parallel to the previous command for which the data is being transferred. 
     At  514 , a determination is made if an error occurred during data transfer and/or command processing (e.g., at  504 ,  508 ,  510 , and/or  512 ). At  516 , if an error occurred during data transfer and/or command processing (e.g., at  504 ,  508 ,  510 , and/or  512 ), the interrupt handling module  230  takes charge and notifies the processing module  202  for further instruction, and the command handling module  220  returns to the idle state. 
     Referring now to  FIG. 6B , a method  600  for status handling according to the present disclosure is shown. At  602 , the status handling module  228  is idle after power on. At  604 , when the SATA controller  108  completes any read/write command, the SATA controller  108  interrupts the processing module  202 . At the same time, the SATA interface module  114  notifies and sends command completion information directly to the status handling module  228 . At  606 , a determination is made if data transfer for current command is completed. At  608 , if data transfer for current command is completed, a determination is made if the data transaction is completed without error. At  610 , the status handling module  228  sends out status without involvement of the processing module  202 . At  612 , if an error occurred in the data transaction, the interrupt handling module  230  notifies the processing module  202  for further instruction. 
     The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. 
     As used herein, the term module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); an electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. The term module may include memory (shared, dedicated, or group) that stores code executed by the processor. 
     The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared, as used above, means that some or all code from multiple modules may be executed using a single (shared) processor. In addition, some or all code from multiple modules may be stored by a single (shared) memory. The term group, as used above, means that some or all code from a single module may be executed using a group of processors. In addition, some or all code from a single module may be stored using a group of memories. 
     The apparatuses and methods described herein may be implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on a non-transitory tangible computer readable medium. The computer programs may also include stored data. Non-limiting examples of the non-transitory tangible computer readable medium are nonvolatile memory, magnetic storage, and optical storage.