Patent Publication Number: US-7904758-B2

Title: System, method and apparatus for tracing source of transmission error

Description:
BACKGROUND OF THE INVENTION 
     Port multipliers and other device multiplexing mechanisms allow a single port to be used for communicating with multiple devices, such as memory drives or peripheral devices. A port multiplier may allow cost-effective scalability in multi-device systems. If any errors are detected in transmission from any one of the devices to the port multiplier, for example, using cyclic redundancy check (CRC), the port multiplier is required to report such errors to the host controller. However, the standard does not provide for the port multiplier to report or differentiate to the host controller which device produced the error. Thus, typically, when an error is detected, either all devices attached to the port multiplier may be reset, or the status of the connected devices must be separately queried. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like reference numerals indicate corresponding, analogous or similar elements, and in which: 
         FIG. 1  shows a schematic diagram of a system including a plurality of devices connected to a host controller through a port multiplier according to embodiments of the present invention; 
         FIG. 2  shows a flowchart of a method according to embodiments of the invention; 
         FIG. 3  shows a flowchart of a method according to embodiments of the invention; and 
         FIG. 4  shows a flowchart of a method according to embodiments of the invention. 
     
    
    
     It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. 
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the invention. However it will be understood by those of ordinary skill in the art that the embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the embodiments of the invention. 
     A data process is here, and generally, considered to be a self-consistent sequence of acts or operations on data leading to a desired result. These include physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers or the like. It should be understood, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. 
     Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining,” or the like, refer to the action and/or processes of a computer or computing system, or similar electronic computing device, that manipulate and/or transform data represented as physical, such as electronic, quantities within the computing system&#39;s registers and/or memories into other data similarly represented as physical quantities within the computing system&#39;s memories, registers or other such information storage, transmission or display devices. 
     Embodiments of the present invention may include apparatuses for performing the operations herein. This apparatus may be specially constructed for the desired purposes, or it may comprise a general purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), electrically programmable read-only memories (EPROMs), electrically erasable and programmable read only memories (EEPROMs), magnetic or optical cards, or any other type of media suitable for storing electronic instructions, and capable of being coupled to a computer system bus. 
     The processes and displays presented herein are not inherently related to any particular computer or other apparatus. Various general purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct a more specialized apparatus to perform the desired method. The desired structure for a variety of these systems will appear from the description below. In addition, embodiments of the present invention are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. 
     Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed at the same point in time. 
     A port multiplier may typically propagate error detection, such as cyclic redundancy check (CRC) error detection to upper layers, including the host controller, such as a serial ATA host controller. According to embodiments of the invention, an indication of data transmission error issued by a port multiplier may include a reference to the specific device that produced the error. Using such a reference, the host controller or a higher layer may be able to reset the specific faulty device rather than, for example, reset the entire subsystem, or initiate a procedure to detect the faulty device, such as querying all devices. 
     Reference is made to  FIG. 1  showing a schematic diagram of a system according to embodiments of the present invention. The system shown in  FIG. 1  includes a plurality of devices  11 ,  12 ,  13  and up to  19  connected to a host controller  30  through a port multiplier  20 . According to some embodiments of the invention, devices  11 ,  12 ,  13  and  19  may be, for example, storage devices such as, but not limited to, floppy disks, optical disks, CD-ROMs, magnetic-optical disks or hard disks. According to some embodiments of the invention, devices  11 ,  12 ,  13  and  19  may be other peripheral devices, such as, but not limited to, network interface cards (NICs), or any other input/output devices. 
     According to some embodiments of the invention, devices  11 ,  12 ,  13 , and  19  may compute an error check parameter for data communicated to port multiplier  20 . For example, a CRC may be computed by these devices. The error check parameter may further be incorporated into data communicated by these devices to port multiplier  20 . 
     According to some embodiments of the invention, port multiplier  20  may receive data and an error check parameter from one of devices  11 ,  12 ,  13 , or  19 . Port multiplier may further verify data integrity by calculating an error check parameter and by further comparing the calculated error check parameter to the received error check parameter. According to some embodiments of the invention, if port multiplier  20  detects an error in the received data, for example by discovering a mismatch between the received error check parameter and a calculated error check parameter then port multiplier  20  may apply a predefined modification to the calculated error check parameter. According to some embodiments of the invention, port multiplier  20  may incorporate a source device identification or a port number into the data communicated to host controller  30 . According to some embodiments of the invention, port multiplier  20  may further incorporate an error check parameter into data communicated to host controller  30 . According to some embodiments of the invention, if port multiplier  20  applied a modification to the error check parameter then port multiplier  20  may incorporate the modified error check parameter into the data communicated to host controller  30 . 
     According to some embodiments of the invention, host controller  30  may receive data from port multiplier  20 . Host controller  30  may calculate an error check parameter and compare it to a received error check parameter. According to some embodiments of the invention, if the error parameters do not show correspondence, host controller  30  may apply a predefined modification to the error check parameter it calculated, and if after the modification the error check parameters do correspond then host controller may deduce that data integrity was violated between one of devices  11 ,  12 ,  13 , or  19  and port multiplier  20 . According to some embodiments of the invention, the identification of the specific device or port from which data was received may be extracted by host controller  30  from data received from port multiplier  20 . It will be understood that in the above, and throughout the present application, two numbers or parameters may correspond in a variety of ways, all intended to be included within the scope of the present invention. For example, correspondence may be shown by two numbers being equal, or otherwise matching, for example by a first number corresponding to or being equaling to a function of the second number, etc. Thus, for example, two numbers may correspond if they are equal, if one numbers equals an inverse of the other number, etc. 
     Reference is now made to  FIG. 2  showing an exemplary functional flowchart of a method performed at a port multiplier according to some embodiments of the invention. At  110  data may be received. For example, a port multiplier may receive data from one of a plurality of connected devices. At block  120  data may be checked for errors. For example, data integrity may be verified in order to discover possible errors, such as but not limited to, transmission errors or memory read and/or write errors. If no errors are found, then the data may be communicated ( 150 ), for example by a port multiplier to a host controller. According to some embodiments of the invention, if errors are found at block  120  then the data may be partially or entirely modified to include a device identification or a port identification as shown by block  130 . Information such as device identification or port number may be readily available to a port multiplier, for example, different devices connected to a port multiplier are connected to separate, discrete ports in the port multiplier, thus a port multiplier may easily associate received data with a source device or a port number. The modified data may be communicated as shown by block  140 , for example, by a port multiplier to a hosting platform. In some embodiments of the invention, the modified data may be communicated together with an error indication. According to some embodiments of the invention, an indication that data communicated at block  140  contains a device and/or port identification may be added to the transaction at block  140 . At the hosting platform, the device identification or port number may be used in order to, for example, reset the relevant device or port. 
     Reference is now made to  FIG. 3  showing an exemplary functional flowchart of a method performed at a host controller connected to a port multiplier according to some embodiments of the invention. At block  210  data may be received, for example by a host controller connected to a hosting platform data bus. In some embodiments of the invention, such controller may further be connected to a port multiplier. Such controller may receive data from a port multiplier at block  210 . At block  220  data may be checked for errors such as but not limited to transmission errors and/or memory read and/or write errors. If no errors are found then data may be communicated as shown by block  230 . For example, a host controller may communicate the data to a driver in the hosting platform or write the data to memory. 
     According to embodiments of the invention, if an error is detected at block  220 , then at block  240  a check may be made in order to determine whether data received at block  210  contains a device identification and/or a port number or port identification. Such indication may have been provided by a port multiplier as described earlier. In some embodiments of the invention, if data received at block  210  contains a device and/or port identification, then such information may be extracted from the data and communicated to upper layers as shown by block  250 , otherwise, an error indication with no specific device or port may be reported to upper layers as shown by block  260 . 
     Reference is now made to  FIG. 4 , showing a functional flowchart diagram illustrating an exemplary method using CRC according to some embodiments of the invention. According to embodiments of the invention, at block  310 , data may be received from any one of a plurality of devices connected to a port multiplier. According to embodiments of the invention, an error checking function may be performed on the content data, and the error checking data included with the data communicated by a connected device. For example, part of the data sent may be used to check for errors, for example, by computing such datum by a sender of data, attaching the datum to the communicated data, computing a datum by a receiver of the communicated data and further comparing received datum to computed datum by a receiver. Error checking computation used in embodiments of the invention may include a redundancy check such as, but not limited to, cyclic redundancy check (CRC), checksum, parity bit value, check digits value, longitudinal redundancy check, horizontal redundancy check, vertical redundancy check, vertical redundancy check, cryptographic message or any other suitable function, for example, any suitable hash function. For simplicity, CRC will be used to exemplify embodiments of the invention, but it will be understood that the invention is not limited to CRC error checking, but rather any suitable error checking process may be used. Accordingly, a first CRC value, CRC 1 , may be computed by a connected device at block  305 . 
     In some embodiments of the invention, the device performing the computation of CRC 1  at block  305  may be any device suitable for connecting to a hosting platform, such as a memory device or a peripheral device. For example, the device may be a storage device such as a hard disk drive, or a removable storage media such as a non-volatile memory device, a compact disk (CD) drive, or the device may be a solid state storage device while data may be a portion of a file, or block of data being read, or data may be some configuration parameters pertaining to the device itself, or any other information stored therein. Data at block  305  may be, for example, read from a device by an application running on the hosting platform. In yet other embodiments of the invention, the device may be a network interface card (NIC) while data may be a packet received from a network. 
     According to embodiments of the invention, the type, configuration and other parameters pertaining to the receiving entity comprising the functionality shown by logical block  310  may vary and may depend on the hosting platform, connected devices, as well as configuration. According to some embodiments of the invention, the receiving entity comprising the functionality shown by logical block  310  may be a port multiplier, such as, but not limited to, advanced technology attachment (ATA) port multiplier, serial advanced technology attachment (SATA) port multiplier, serial advanced technology attachment II (SATA II) port multiplier, external serial advanced technology attachment (eSATA), or any other suitable port multiplier. 
     According to embodiments of the invention, at block  310  CRC 2  of the received data may be computed. According to embodiments of the invention, the computation of CRC 2  may be performed in the same fashion and/or according to the same scheme as the computation of CRC 1 . Consequently, if data integrity has been preserved, it may be expected that CRC 1  will correspond to CRC 2 . 
     According to embodiments of the invention, information identifying the source of data may be incorporated into the received data as shown by block  312 . For example, if the functionality shown by logical block  312  is performed by a port multiplier, then information identifying the device and/or port from which data was received at block  310  may be incorporated into the data received. According to embodiments of the invention, CRC 3  may be computed for the modified data at block  312 . According to the embodiments of the invention, the computation of CRC 3  may be performed in the same fashion and/or according to the same scheme as the computation of CRC 1  and CRC 2 . 
     In some embodiments of the invention, the port multiplier may calculate an error check parameter based on the data and the identity of the device that produced the data, for example, so that the error check may relate to the integrity of the entirety of data transmitted by the port multiplier to the host controller. It will be noted, however, that the invention is not limited in this regard, and the error check may be separately calculated on any single one or more components of the information transmitted by the port multiplier, e.g., the received data and the identity of the device. 
     According to embodiments of the invention, CRC 1  and CRC 2  may be compared as shown by block  315 . According to some embodiments of the invention, if CRC 1  corresponds to CRC 2  then it may be assumed that data integrity has been preserved during transmission from block  305  to block  310 . In such case, data may be communicated with newly computed CRC 3  as shown by block  330 . According to embodiments of the invention, communication of the data and CRC 3  as shown by block  330  may be from a port multiplier to a hosting platform. 
     According to embodiments of the invention, if CRC 1  does not correspond to CRC 2  at block  315  then it may be presumed data integrity has been violated between block  305  and block  310 . In such case, according to embodiments of the invention, CRC 3  may be modified at block  325  according to a predefined rule. According to some embodiments of the invention, modification of CRC 3  may be reversible. For example, CRC 3  may be modified at block  325  by bit inversion, namely, by inverting its binary representation such that all 1&#39;s are replaced by 0&#39;s and all 0&#39;s are replaced by 1&#39;s. According to other embodiments of the invention, CRC 3  may be modified, or derived, at block  325  by an irreversible function. For example, CRC 3  may be assigned a constant value, e.g. 0 (zero) or −1 (minus one). As will be described below, such predefined values may be interpreted, for example by a receiving entity of CRC 3  as an indication that data integrity violation has been detected at block  315  and possibly, further, that a device identification has been incorporated into the data. According to embodiments of the invention, the modified CRC 3  may be communicated with the data as shown by block  330 . 
     According to embodiments of the invention, communicated data and a CRC from block  330  may be received at block  340 . Accordingly, the CRC received at block  340  may be either a modified CRC 3  or an unmodified CRC 3 . For reference purposes, the CRC received at block  340  will be denoted CRCr hereafter. 
     According to embodiments of the invention, CRC 4  for the data received at block  340  may be computed as shown by block  345 . According to embodiments of the invention, CRC 4  may be computed in the same fashion and/or according to the same scheme as the computation of CRC 1  and/or CRC 2 . CRC 4  may further be compared with CRCr at block  350 . 
     According to some embodiments of the invention, if CRC 4  is found to correspond to CRCr at block  350  then it may be presumed data integrity has been preserved. Further actions may comprise, for example, copying of data to its destination memory within a hosting platform, and/or notifying an application of the arrival of new data ( 335 ). 
     According to some embodiments of the invention, if CRC 4  is found to be different from CRCr at block  350  then CRC 4  may be modified at block  360 . According to some embodiments of the invention, modifications applied to CRC 4  may be the same as those applied to CRC 3  at block  325 . In other embodiments of the invention, instead of modifying CRC 4  at block  360 , CRCr may be modified in a manner that reverts the modifications applied to CRC 3 , possibly at block  325 . For example, if bit inversion was used to modify CRC 3  at block  325  then applying bit inversion to CRCr may revert its value back to the value of CRC 3  before the modification at block  325 . In other embodiments of the invention, if CRC 4  is found to be different from CRCr at block  350  then the value of CRCr may be compared to a predefined value, for example 0 (zero) or −1 (minus one). 
     According to some embodiments of the invention, if CRC 4  was modified at block  360  then modified CRC 4  may be compared to CRCr at block  370 . If CRCr was modified at block  360 , then modified CRCr may be compared to CRC 4  at block  370 . If the compared CRC&#39;s are found to correspond at block  370 , or CRCr corresponds to a predefined value as described above, it may be presumed that data integrity has been violated between block  305  and block  310 . For example, between a source device and a port multiplier. Further action may comprise retrieving device identification and/or port identification or number that may have been incorporated into the data at block  312  and possibly informing upper layers of both the error and the identification of the device as shown by block  385 . According to embodiments of the invention, upper layers, or the layer performing the functionalities comprising the functionality of block  370  may use the device and/or port identification in order to, for example, reset the specific device or port, as well as possibly collect statistics. 
     According to some-embodiments of the invention, If the compared CRC&#39;s are found to be different at block  370  it may be presumed that data integrity has been violated between block  335  and block  340 . For example, between a port multiplier and a controller at the hosting platform. Further action may comprise informing upper layers of the error as shown by block  380 . 
     In some embodiments of the invention, the entity performing the functionalities from block  340  through block  385  may be a controller attached to a hosting platform bus. For example, a port multiplier enabled controller, such as but not limited to, a controller supporting command-based switching or a controller supporting frame information structure (FIS), or any other suitable controller or device. 
     While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the spirit of the invention.