JP5334173B2 - Data transfer system and retry control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data transfer system for suppressing deterioration in performance by reducing the frequency of retries. <P>SOLUTION: A data processor 1 is provided with: a transmission synchronization buffer 103 for storing data to be transmitted; and a read control means 110 for controlling read of data from the transmission synchronization buffer 103. A data processor 2 is provided with: a reception synchronization buffer 211 for storing received data; and a retry request generation means 213 for, when the data cannot be received since the reception synchronization buffer 211 is busy, requesting the retry of data transmission to the data processor 1. The read control means 110 obtains a reference time corresponding to the occurrence interval of the retry request, and controls read of data from the transmission synchronization buffer 103 based on the reference time. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a data transfer system and a retry control method in the system.

  Patent Document 1 below discloses a data transfer system in which a data buffer unit is connected between a first bus and a second bus. Data is transferred from the first bus to the second bus by writing data from the first bus to the buffer memory of the data buffer unit, reading the data from the buffer memory, and transmitting the data to the second bus. When a retry request is generated from the second bus, the data held in the data buffer unit is rewritten to the buffer memory, so that the data is read again from the buffer memory and the second bus. Sent to.

  Patent Document 2 below discloses a data transfer system in which a bus bridge is connected between a high-speed bus and a low-speed bus. If a read access request from the high-speed bus to the low-speed bus occurs when the low-speed bus is busy, the bus bridge sends a retry request to the master device of the high-speed bus and stores the access address. When the busy state of the low-speed bus is resolved, the bus bridge writes an access address to the low-speed bus device, and the master device of the high-speed bus executes a read operation with one access at the time of retry.

  Patent Document 3 below discloses a library apparatus capable of executing a retry process. If the retry process is unsuccessful, the measuring means measures the time required for the retry process (actual retry operation time). The comparison means compares the substantial retry operation time with a predetermined total retry time. When the actual retry operation time is equal to or less than the total retry time, the retry process is continued. On the other hand, when the actual retry operation time is larger than the total retry time, a timeout is notified to the host device.

JP-A-9-274594 Japanese Patent Laid-Open No. 10-4420 Japanese Patent Laid-Open No. 4-76854

  As disclosed in the above Patent Documents 1 to 3, when a certain process is unsuccessful, control for executing a retry process of the process is widely known. However, when the retry process is executed, the time for executing the original process (a normal process other than the retry process) is reduced by the retry process. Accordingly, when the frequency of the retry process is increased, the time to be reduced is also increased, so that the performance related to the original process is deteriorated.

  The present invention has been made in view of such circumstances, and to obtain a data transfer system and a retry control method in the system capable of suppressing a decrease in performance by reducing the frequency of occurrence of retry processing. It is the purpose.

A data transfer system according to the present invention includes a first data processing device and a second data processing device that receives data transmitted from the first data processing device, and the first data processing device includes: A transmission buffer for storing data to be transmitted; and a read control unit for controlling reading of data from the transmission buffer; the second data processing device includes a reception buffer for storing received data; A retry control unit that requests the first data processing device to retry data transmission when data cannot be received because the reception buffer is busy, and the read control unit A reference time corresponding to a request generation interval is obtained, and reading of data from the transmission buffer is controlled based on the reference time. Than is.

  In the retry control method according to the present invention, (A) a step of reading data stored in a transmission buffer included in the first data processing device and transmitting the data to a second data processing device; Requesting data transmission retry from the second data processing device to the first data processing device when data cannot be received because the reception buffer of the second data processing device is busy; , (C) obtaining a reference time corresponding to the generation interval of retry requests, and (D) controlling the reading of data from the transmission buffer based on the reference time. is there.

  According to the present invention, it is possible to suppress a decrease in performance by reducing the frequency of retry processing.

It is a block diagram which shows the structure of the data transfer system which concerns on embodiment of this invention. It is a block diagram which shows the structure of the data transfer system which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the element which attached | subjected the same code | symbol in different drawing shall show the same or corresponding element.

  1 and 2 are block diagrams showing the configuration of the data transfer system according to the embodiment of the present invention. As shown in FIGS. 1 and 2, the data transfer system according to the present embodiment includes data processing devices 1 and 2 such as LSIs, and wirings 10 and 20 that connect them. The wiring 10 connects the output terminal 151 of the data processing device 1 and the input terminal 252 of the data processing device 2. The wiring 20 connects the output terminal 251 of the data processing device 2 and the input terminal 152 of the data processing device 1.

  As shown in the connection relationship of FIG. 1, the data processing apparatus 1 includes a transmission data holding unit 100, a retry buffer 101, a selector 102, a transmission synchronization buffer 103, a transmission busy control unit 104, a retry request detection unit 105, and a determination unit 106. , Retry count holding means 107, retry interval holding means 108, timer 109, read control means 110, reception synchronization buffer 111, reception busy control means 112, retry request generation means 113, retry execution means 114, and received data holding means 115 It is configured with. In addition, as indicated by a broken line in FIG. 1, the data processing device 1 is based on a clock domain that operates based on a clock CLK1 having a predetermined frequency (hereinafter referred to as “CLK1 domain”) and a clock CLK2 that has a different frequency. Are divided into clock domains (hereinafter referred to as “CLK2 domains”).

Transmission data holding means 100 holds data to be transmitted, and transmission busy control means 104.
If the data suppression request is not received from, the stored data is output. The retry buffer 101 holds the data input from the transmission data holding unit 100, and outputs the held data when a retry execution request is received from the retry execution unit 114. The selector 102 selects and outputs one of the output data from the transmission data holding unit 100, the output data from the retry buffer 101, and the output data from the retry request generation unit 113.

  The transmission synchronization buffer 103 stores the data input from the selector 102, performs synchronization from the CLK1 domain to the CLK2 domain, and then reads and outputs the data based on the read request from the read control means 110. The transmission busy control unit 104 performs busy management of the transmission synchronization buffer 103. Data output from the transmission synchronization buffer 103 is transmitted toward the data processing device 2 via the output terminal 151 and the wiring 10. That is, the transmission synchronization buffer 103 functions as a transmission buffer that stores data to be transmitted to the data processing device 2.

  The retry request detection unit 105 detects a retry request received from the data processing device 2 via the wiring 20 and the input terminal 152. When the retry request detecting unit 105 detects a retry request, the retry number holding unit 107 increments its own counter and holds the value of the counter. When the retry request detection unit 105 detects a retry request, the retry interval holding unit 108 holds the value of the timer 109 at the time of detection. The read control unit 110 performs read control of the transmission synchronization buffer 103 based on the values held by the retry number holding unit 107 and the retry interval holding unit 108, respectively. That is, the read control unit 110 functions as a read control unit that controls reading of data from the transmission synchronization buffer 103.

  The determination unit 106 determines whether data can be stored in the reception synchronization buffer 111 based on the data received from the data processing device 2 via the wiring 20 and the input terminal 152 and the output of the reception busy control unit 112. To do. When it is determined that the reception synchronization buffer 111 is busy, a predetermined busy flag is added to the data and output. On the other hand, when it is determined that the reception synchronization buffer 111 is not busy, data is output without adding a busy flag.

  The reception synchronization buffer 111 stores the data input from the determination unit 106, and outputs the data after performing synchronization from the CLK2 domain to the CLK1 domain. That is, the reception synchronization buffer 111 functions as a reception buffer that stores data received from the data processing device 2. The reception busy control unit 112 performs busy management of the reception synchronization buffer 111. When the busy flag is added to the data output from the reception synchronization buffer 111, the retry request generation unit 113 generates a retry request for requesting the data processing device 2 to retransmit the data. That is, the retry request generation unit 113 functions as a retry control unit that requests the data processing device 2 to retry data transmission.

  The retry execution unit 114 requests the retry buffer 101 to start retry processing when the output of the reception synchronization buffer 111 is a retry request. The reception data holding means 115 stores normal data excluding data to which a retry request or a busy flag is added from among data output from the reception synchronization buffer 111.

The data processing device 2 has the same configuration as the data processing device 1. As shown in the connection relationship of FIG. 2, the data processing apparatus 2 includes a transmission data holding unit 200, a retry buffer 201, a selector 202, a transmission synchronization buffer 203, a transmission busy control unit 204, a retry request detection unit 205, and a determination unit 206. , Retry number holding means 207, retry interval holding means 208, timer 209, read control means 210, reception synchronization buffer 211, reception busy control means 212, retry request generation means 213, retry execution means 214, and received data holding means 215. It is configured with. Further, as indicated by a broken line in FIG. 2, the data processing device 2 is divided into a CLK1 domain and a CLK2 domain.

  The transmission data holding unit 200 holds data to be transmitted, and outputs the held data when no data suppression request is received from the transmission busy control unit 204. The retry buffer 201 holds data input from the transmission data holding unit 200 and outputs the held data when a retry execution request is received from the retry execution unit 214. The selector 202 selects and outputs one of output data from the transmission data holding unit 200, output data from the retry buffer 201, and output data from the retry request generation unit 213.

  The transmission synchronization buffer 203 stores the data input from the selector 202, performs synchronization from the CLK1 domain to the CLK2 domain, and then reads and outputs the data based on the read request from the read control unit 210. The transmission busy control means 204 performs busy management of the transmission synchronization buffer 203. Data output from the transmission synchronization buffer 203 is transmitted to the data processing apparatus 1 via the output terminal 251 and the wiring 20. That is, the transmission synchronization buffer 203 functions as a transmission buffer that stores data to be transmitted to the data processing device 1.

  The retry request detection unit 205 detects a retry request received from the data processing apparatus 1 via the wiring 10 and the input terminal 252. When the retry request detecting unit 205 detects a retry request, the retry number holding unit 207 increments its own counter and holds the value of the counter. When the retry request detecting unit 205 detects a retry request, the retry interval holding unit 208 holds the value of the timer 209 at the time of detection. The read control unit 210 performs read control of the transmission synchronization buffer 203 based on the values held by the retry count holding unit 207 and the retry interval holding unit 208, respectively. That is, the read control unit 210 functions as a read control unit that controls reading of data from the transmission synchronization buffer 203.

  The determination unit 206 determines whether data can be stored in the reception synchronization buffer 211 based on the data received from the data processing device 1 via the wiring 10 and the input terminal 252 and the output of the reception busy control unit 212. To do. When it is determined that the reception synchronization buffer 211 is busy, a predetermined busy flag is added to the data and output. On the other hand, if it is determined that the reception synchronization buffer 211 is not busy, data is output without adding a busy flag.

  The reception synchronization buffer 211 stores the data input from the determination unit 206, and outputs the data after performing synchronization from the CLK2 domain to the CLK1 domain. That is, the reception synchronization buffer 211 functions as a reception buffer that stores data received from the data processing device 1. The reception busy control unit 212 performs busy management of the reception synchronization buffer 211. When the busy flag is added to the data output from the reception synchronization buffer 211, the retry request generation unit 213 generates a retry request for requesting the data processing device 1 to retransmit the data. That is, the retry request generation unit 213 functions as a retry control unit that requests the data processing device 1 to retry data transmission.

The retry execution unit 214 requests the retry buffer 201 to start retry processing when the output of the reception synchronization buffer 211 is a retry request. The reception data holding unit 215 stores normal data excluding data to which a retry request or a busy flag is added from among data output from the reception synchronization buffer 211.

  Hereinafter, an operation when data is transmitted from the data processing device 1 to the data processing device 2 when the reception synchronization buffer 211 is busy will be described. That is, in the following example, the data processing device 1 is a transmission side LSI, and the data processing device 2 is a reception side LSI. Since the data processing device 1 and the data processing device 2 have the same configuration, data is transferred from the data processing device 2 to the data processing device 1 by performing processing opposite to the following description. It is also possible to transmit.

  Referring to FIG. 2, the data transmitted from data processing apparatus 1 is input to determination means 206 via wiring 10 and input terminal 252. If the determination unit 206 determines that the reception synchronization buffer 211 is busy based on the type of data input from the data processing device 1 and the busy signal input from the reception busy control unit 212, the data Is added to the reception synchronization buffer 211 after adding a busy flag. Further, the determination unit 206 discards subsequent data input from the data processing apparatus 1 following the data until the retry data of the data is later input again from the data processing apparatus 1 by the retry processing. That is, storage of data in the reception synchronization buffer 211 is suppressed. In this way, by discarding subsequent data in the determination unit 206, it is possible to avoid overwriting of subsequent data in the reception synchronization buffer 211.

  The reception synchronization buffer 211 stores the data with the busy flag input from the determination unit 206, and after synchronizing from the CLK2 domain to the CLK1 domain, outputs the data with the busy flag.

  The data with the busy flag output from the reception synchronization buffer 211 is not stored in the reception data holding unit 215 but is input to the retry request generation unit 213. The retry request generation unit 213 generates and outputs a retry request command including necessary information such as a read pointer of the retry buffer 101 based on the input data with the busy flag. The retry request output from the retry request generation unit 213 is input to the transmission synchronization buffer 203 via the selector 202.

  The transmission synchronization buffer 203 stores the retry request input from the selector 202, and outputs it after synchronizing from the CLK1 domain to the CLK2 domain. The retry request output from the transmission synchronization buffer 203 is transmitted to the data processing apparatus 1 via the output terminal 251 and the wiring 20.

  With reference to FIG. 1, the retry request detection unit 105 detects the first retry request received from the data processing device 2 via the wiring 20 and the input terminal 152. When the retry request detecting unit 105 detects the first retry request, the retry number holding unit 107 resets its counter, increments the counter value by “1”, and holds the counter value. When the retry request detecting unit 105 detects the first retry request, the retry interval holding unit 108 resets the timer 109 and then sets the value of the timer 109 at the time of detection (in the case of detecting the first retry request). Holds “0” by resetting). Thereafter, the timer 109 starts an elapsed time counting operation.

A retry request received from the data processing device 2 via the wiring 20 and the input terminal 152 is input to the determination unit 106. If the reception synchronization buffer 111 is not busy, the determination unit 106 inputs the retry request to the reception synchronization buffer 111. The reception synchronization buffer 111 stores the retry request input from the determination unit 106, and after synchronizing from the CLK2 domain to the CLK1 domain, outputs the retry request.

  The retry request output from the reception synchronization buffer 111 is not stored in the reception data holding unit 115 but is input to the retry execution unit 114. When the retry execution unit 114 accepts the retry request, the retry execution unit 114 extracts information such as a read pointer from the retry request and inputs the information to the retry buffer 101. The retry buffer 101 reads out and outputs data targeted for retry processing based on the information input from the retry execution means 114.

  Data output from the retry buffer 101 (referred to as “retry data”) is input to the transmission synchronization buffer 103 via the selector 102. The transmission synchronization buffer 103 stores the retry data input from the selector 102, and outputs it after synchronizing from the CLK1 domain to the CLK2 domain. The retry data output from the transmission synchronization buffer 103 is transmitted to the data processing device 2 via the output terminal 151 and the wiring 10.

  Referring to FIG. 2, the retry data transmitted from data processing device 1 is input to determination means 206. If the determination unit 206 determines that the input data is the head of the retry data, the determination unit 206 cancels the suppression of data storage in the reception synchronization buffer 211. As a result, the retry data is stored in the reception synchronization buffer 211 from the determination unit 206. The reception synchronization buffer 211 outputs the retry data input from the determination unit 206 after performing synchronization from the CLK2 domain to the CLK1 domain. The retry data output from the reception synchronization buffer 211 is stored in the reception data holding unit 215.

  When the transmission of data from the data processing device 1 to the data processing device 2 continues and the necessity of the retry processing occurs again, transmission of a retry request from the data processing device 2 to the data processing device 1 as described above, Transmission of retry data from the data processing device 1 to the data processing device 2 is executed.

  Referring to FIG. 1, every time retry request detecting means 105 detects a retry request, retry number holding means 107 increments its own counter value by “1” and holds the counter value. Here, a predetermined threshold value (hereinafter referred to as “threshold value X”) relating to the counter value is set in advance in the retry count holding means 107 and the retry interval holding means 108. When the counter value reaches the threshold value X, the retry count holding unit 107 inputs a signal indicating that to the retry interval holding unit 108. Retry interval holding means 108 stops the operation of timer 109 when the signal is input from retry number holding means 107 and divides the value of timer 109 at that time by threshold value X. As a result, the average value of the retry request generation intervals is obtained. The retry interval holding unit 108 sets and stores the obtained average value (preferably a value smaller by several percent) as a reference time for the retry interval. When the setting of the reference time is completed, the counter value of the retry count holding means 107 is reset. Further, the value of the timer 109 is also reset, and the timer 109 restarts counting the elapsed time from “0”.

When the value of the timer 109 reaches the reference time stored in the retry interval holding unit 108, the read control unit 110 performs transmission synchronization even if transmission data exists in the transmission synchronization buffer 103. The transmission data read from the data buffer 103 is paused for a certain time (for example, a time corresponding to one read cycle). When the fixed time has elapsed, the value of the timer 109 is reset and reading of transmission data from the transmission synchronization buffer 103 is resumed. Thereafter, by repeating the same operation, the reading of the transmission data is temporarily suspended every time the reference time elapses after the reading of the transmission data from the transmission synchronization buffer 103 is started.

  In addition, the read control unit 110 can update the reference time stored in the retry interval holding unit 108 in accordance with the generation status of the retry request in the operation after the reference time is set. By updating the reference time, it is possible to perform an appropriate operation according to the generation status of the retry request.

  For example, a predetermined threshold value (hereinafter referred to as “threshold value Y”) relating to the counter value is preset in the retry count holding means 107. The retry count holding means 107 increments its own counter value by “1” every time the retry request detecting means 105 detects a retry request even in the operation after the reference time is set, and holds the counter value. To do. When the counter value reaches the threshold value Y, the retry count holding unit 107 inputs a signal indicating that to the read control unit 110. As an example, the read control unit 110 sets the reference time to the current value if the elapsed time is relatively long according to the elapsed time from when the reference time is set until the signal is received from the retry count holding unit 107. If the elapsed time is relatively short, the reference time is updated to a value significantly smaller than the current value.

  Further, for example, the retry request detecting means 105 is preset with a predetermined threshold relating to elapsed time (hereinafter referred to as “threshold Z”). If the retry request detection unit 105 does not detect a retry request even after the time corresponding to the threshold value Z has elapsed in the operation after the reference time is set, the read control unit 110 sends a signal indicating that fact. To enter. When the read control means 110 receives the signal from the retry request detection means 105, the read control means 110 updates the reference time to a value that is larger than the current value by a predetermined time (for example, time corresponding to one cycle).

  As described above, according to the data transfer system according to the present embodiment, the data processing device 1 transmits the data to be transmitted from the transmission synchronization buffer 103 (transmission buffer) for storing the data to be transmitted and the data from the transmission synchronization buffer 103. Read control means 110 (reading control unit) for controlling the above. In addition, the data processing device 2 receives the data synchronization device 211 when the reception synchronization buffer 211 (reception buffer) for storing the received data and the reception synchronization buffer 211 cannot receive data because the reception synchronization buffer 211 is busy. And retry request generating means 213 (retry control unit) for requesting data transmission retry. Then, the read control unit 110 obtains a reference time corresponding to the retry request generation interval, and controls reading of data from the transmission synchronization buffer 103 based on the reference time. Specifically, the reading of data from the transmission synchronization buffer 103 is temporarily suspended when the reference time has elapsed since the start of reading of data from the transmission synchronization buffer 103. As a result, transmission of data from the data processing device 1 to the data processing device 2 is also temporarily suspended, and the reception synchronization buffer 211 can proceed with processing during that time, so that a retry request is generated in the data processing device 2. The frequency can be reduced. As a result, it is possible to reduce the amount of time required for executing the original process (normal process that is not the retry process) to be reduced by the retry process, and thus it is possible to suppress a decrease in performance related to the original process. .

DESCRIPTION OF SYMBOLS 1, 2 Data processing apparatus 103 Transmission synchronization buffer 105 Retry request detection means 107 Retry number holding means 108 Retry interval holding means 109 Timer 110 Read control means 206 Judgment means 211 Reception synchronization buffer 213 Retry request generation means

Claims (4)

A first data processing device;
A second data processing device for receiving data transmitted from the first data processing device,
The first data processing device includes:
A transmission buffer for storing data to be transmitted;
A read control unit that controls reading of data from the transmission buffer;
The second data processing device includes:
A receive buffer to store the received data;
A retry control unit that requests the first data processing device to retry data transmission when the reception buffer is in a busy state and cannot receive data;
The read control unit obtains a reference time corresponding to a retry request generation interval, starts reading data from the transmission buffer, and when the obtained reference time has elapsed, the data from the transmission buffer Data transfer system that temporarily stops reading data. The data transfer system according to claim 1, wherein the read control unit updates the reference time according to a generation status of a retry request. When the second data processing device cannot receive data because the reception buffer is busy, the second data processing device transmits subsequent data to the reception buffer until the data is received again in response to a retry request. The data transfer system according to claim 1 or 2 , wherein the data transfer system is discarded without being stored. (A) reading the data stored in the transmission buffer of the first data processing device and transmitting it to the second data processing device;
(B) Retrying data transmission from the second data processing device to the first data processing device when data cannot be received because the reception buffer of the second data processing device is busy. Requesting, and
(C) obtaining a reference time according to the generation interval of the retry request;
(D) a retry control method comprising: temporarily stopping reading of data from the transmission buffer when the obtained reference time has elapsed after starting reading of data from the transmission buffer .

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