Abstract:
An apparatus and method of dynamic resource mapping for isolating interrupt sources is implemented. Each interrupt source is provided with a unique identifier. The identifier is mapped to an interrupt number which is sent to an operating system when the interrupt source corresponding to the identifier generates an interrupt. Each device is associated with a data structure that includes a data value which is operable for accessing an interrupt register. The data value may be a pointer that points to a pointer to the interrupt register for the device generating the interrupt. When an interrupt is generated, the mapping may be used to access the pointers which thereby provide direct access to the interrupt register, whereby the contents of the interrupt register are processed by an interrupt service routine.

Description:
TECHNICAL FIELD 
     The present invention relates in general to data processing systems, and in particular, to interrupt isolation and handling in data processing systems. 
     BACKGROUND INFORMATION 
     Modern data processing systems may have many attached remote peripheral units, numbering in the tens, or more. Each of these remote units may be the source of an interrupt that the operating system (OS) must isolate and handle. Moreover, it is the nature of most interrupts that they require immediate attention. For example, a peripheral device may monitor its environment, and generate an interrupt if an environmental problem, such as over temperature, fan loss or power loss occurs. These environmental problems may require immediate attention in order to preserve data integrity, and prevent the hardware from becoming permanently damaged. 
     Interrupt isolation mechanisms examine each of the attached peripheral units. The operating system traverses the attached peripheral units until a device having a set interrupt register is found Having thus isolated the source of the interrupt, the OS can service the interrupt. Having to examine each of the attached peripheral units, until the interrupt source is found can introduce a significant delay in overall data processing system speed. Thus, there is a need in the art for apparatus and methods to reduce the time needed to isolate interrupt sources, and thereby improve the handling of interrupts. 
     SUMMARY OF THE INVENTION 
     The aforementioned needs are addressed by the present invention. Accordingly, there is provided, in a first form, a method of dynamic resource mapping for isolating interrupt sources. The method includes providing a plurality of interrupt source device identifiers, wherein each identifier corresponds to one of a plurality of interrupt sources. A table mapping the interrupt source identifiers to corresponding interrupt numbers is generated, and an interrupt, represented by one of the interrupt numbers, is associated with a corresponding device generating the interrupt using the table. 
     There is also provided, in a second form, a data processing system having a central processing unit (CPU), wherein a plurality of peripheral devices are coupled to the CPU. The CPU includes circuitry operable for dynamic resource mapping for isolating interrupts from the plurality of peripheral devices, which circuitry includes circuitry operable for providing a plurality of interrupt source device identifiers. Each identifier corresponds to one of the plurality of peripheral devices. Also included is circuitry operable for generating a table mapping the interrupt source identifiers to corresponding interrupt numbers, and circuitry operable for associating an interrupt, represented by one of the interrupt numbers, with a corresponding device generating the interrupt using the table. 
     Additionally, there is provided, in a third form, a program product in a computer readable medium for dynamic resource mapping for isolating interrupt sources. The program product has programming for providing a plurality of interrupt source device identifiers, wherein each identifier corresponds to one of a plurality of interrupt sources. Also included is programming for generating a table mapping the interrupt source identifiers to corresponding interrupt numbers, and programming for associating an interrupt, represented by one of the interrupt numbers, with a corresponding device generating the interrupt using the table. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 illustrates, in block diagram form, a data processing system in accordance with an embodiment of the present invention; 
     FIG. 2 illustrates, in flowchart form, a method of interrupt isolation in accordance with an embodiment of the present invention; 
     FIG. 3 schematically illustrates an interrupt table according to an embodiment of the present invention; 
     FIG. 4 schematically illustrates a data structure in accordance with an embodiment of the present invention; 
     FIG. 5 schematically illustrates an interrupt vector table according to an embodiment of the present invention; and 
     FIG. 6 schematically illustrates a memory space associated with an interrupt source in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention provides a dynamic resource mapping mechanism for isolating interrupt sources. Each peripheral device that is capable of interrupting the operating system (OS) is assigned an interrupt number. The device is also provided with a unique device identifier (ID), which may be stored and later retrieved from the device. A mapping of the interrupt number to the device ID is created and provided to runtime firmware. Using this mapping, the OS can isolate and service the interrupt using the device ID in the map table to go directly to an interrupt service routine for the interrupting device 
     In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. In other instances, well-known circuits have been shown in block diagram form in order not to obscure the present invention in unnecessary detail. 
     Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views. 
     Referring first to FIG. 1, an example is shown of a data processing system  100  which may be used for the invention. The system has a central processing unit (CPU)  110 , which is coupled to various other components by system bus  112 . Read only memory (“ROM”)  116  is coupled to the system bus  112  and includes a basic input/output system (“BIOS”) that controls certain basic functions of the data processing system  100 . Random access memory (“RAM”)  114 , I/O adapter  118 , and communications adapter  134  are also coupled to the system bus  112 . I/O adapter  118  may be a small computer system interface (“SCSI”) adapter that communicates with a disk storage device  120 . Communications adapter  134  interconnects bus  112  with an outside network enabling the data processing system to communicate with other such systems. Input/Output devices are also connected to system bus  112  via user interface adapter  122  and display adapter  136 . Keyboard  124 , track ball  132 , mouse  126  and speaker  128  are all interconnected to bus  112  via user interface adapter  122 . Display monitor  138  is connected to system bus  112  by display adapter  136 . In this manner, a user is capable of inputting to the system throughout the keyboard  124 , trackball  132  or mouse  126  and receiving output from the system via speaker  128  and display  138 . 
     Preferred implementations of the invention include implementations as a computer system programmed to execute the method or methods described herein, and as a computer program product. According to the computer system implementation, sets of instructions for executing the method or methods are resident in the random access memory  114  of one or more computer systems configured generally as described above. Until required by the computer system, the set of instructions may be stored as a computer program product in ROM  116 , or in another computer memory, for example, in disk drive  120  (which may include a removable memory such as an optical disk or floppy disk for eventual use in the disk drive  120 ). Further, the computer program product can also be stored at another computer and transmitted when desired to the user&#39;s work station by a network or by an external network such as the Internet. One skilled in the art would appreciate that the physical storage of the sets of instructions physically changes the medium upon which it is stored so that the medium carries computer readable information. The change may be electrical, magnetic, chemical, biological, or some other physical change. While it is convenient to describe the invention in terms of instructions, symbols, characters, or the like, the reader should remember that all of these and similar terms should be associated with the appropriate physical elements. 
     Note that the invention may describe terms such as comparing, validating, selecting, identifying, or other terms that could be associated with a human operator. However, for at least a number of the operations described herein which form part of at least one of the embodiments, no action by a human operator is desirable. The operations described are, in large part, machine operations processing electrical signals to generate other electrical signals. 
     Refer now to FIG. 2 in which is illustrated a method  200  for isolating interrupt sources in accordance with an embodiment of the present invention. In step  202 , data processing system launches boot firmware, which may be located in ROM  116  in FIG.  1 . CPU  110  vectors to the boot firmware which loads itself and run time firmware (RTF) segments into RAM  114  and initiates system initialization. 
     In step  204 , the boot firmware maps each physical peripheral interrupt source with a logical interrupt number. The interrupt number corresponds to a physical structure for communicating the interrupt to the CPU, usually a line in the bus connecting the peripheral to the system. However, the interrupt number is not otherwise associated with a physical interrupt source device until the mapping is constructed by the boot firmware. Each physical interrupt source is provided with a unique physical device identifier (UDID). Each device UDID uniquely identifies the associated device, and may be drawn from a predetermined set of UDIDs provided in the firmware. The UDID may be stored in the device and later retrieved therefrom. Alternative configurations of data processing system  200  may include first and second pluralities of such peripheral devices which differ from each other in number and type of device. The boot firmware probes the bus to locate these devices and assigns the UDID. For peripheral devices that are constant across embodiments, a UDID may be statically assigned. A table mapping interrupt numbers to device UDIDs is built by the boot firmware in response thereto. 
     An exemplary interrupt table is illustrated in FIG.  3 . Table  300  includes a plurality, k, of entries  302  corresponding to a plurality of peripheral interrupt sources. An interrupt number (INUM) is contained in field  304  and the corresponding UDID mapped to the INUM is included in field  306 . 
     In an embodiment of the present invention, peripheral devices may be devices in accordance with the Peripheral Component Interconnect (PCI) protocol. In such an embodiment, the device ID may be a PCI configuration space address (CSA). Thus, for example, in an embodiment in which disk storage device  120  is a SCSI disk, I/O adapter  118  may include a PCI SCSI bus controller. Similarly, communications adapter  134  may include PCI peripheral devices for coupling system bus  112  (a portion of which may be a PCI bus) to network  142 , which PCI device might be, for example, a Token ring controller or an Ethernet controller, depending on the particular architecture of network  142 . Thus, it would be understood by one of ordinary skill in the art that data processing system  100  in accordance with an embodiment of a present invention may include a plurality of PCI devices. In such an embodiment, the PCI CSA may serve to uniquely identify a corresponding physical PCI peripheral device. 
     Alternatively, in an embodiment of the present invention, including non-PCI peripherals, a predetermined set of identifiers is provided. Each identifier in the predetermined set is associated with a corresponding physical device. In step  206 , the boot firmware uses this association to generate the hardware map tables mapping interrupt numbers to physical devices. 
     The boot firmware then loads runtime firmware (RTF), step  208 . The RTF includes routines for servicing hardware devices, and, in particular, servicing interrupts generated by the peripheral devices. The boot firmware initiates OS boot. The OS provides space for the RTF to be loaded in OS space in a portion of RAM  114  and calls the boot firmware to copy the RTF segments loaded in step  202  into the space provided by the OS. The RTF environment is initialized, in step  208 , by the boot firmware which passes the arguments required by the RTF. When the RTF environment is initialized by the boot firmware, the boot firmware passes the interrupt map tables generated in step  206  to the RTF. 
     In step  210 , the RTF builds peripheral device data structures. The RTF is device aware, having information related to each peripheral device attached to the data processing system, such as data processing system  100  in FIG.  1 . The RTF builds a data structure corresponding to each peripheral device in the data processing system. Included in the data structure for each device is the corresponding device UDID, which the RTF may read from preselected devices. Additionally, the UDID may be coded into the RTF for other preselected devices. In this way, the RTF associates the unique UDID with the associated physical device. 
     Also associated with each peripheral device may be one or more memory spaces (which may also be referred to as register spaces) for containing control information and data related to the device. For example, in an embodiment of the present invention in which the peripheral devices may be PCI devices, each peripheral device may have a corresponding input/output (I/O) address space, and a corresponding memory address space. In such an embodiment, reads from and writes to the peripheral device are implemented as reads from, and writes to, respectively, the corresponding I/O address space. The I/O address space may also be used by the operating system to communicate control signals between the corresponding peripheral device and the operating system. The memory address space associated with a particular peripheral device may be used to hold data to be communicated to the device. 
     This may be understood by referring to FIG. 4 illustrating a data structure  400  in accordance with one embodiment of the present invention. Data structure  400  includes a plurality of entries, in which entry  402  may include the UDID corresponding to the peripheral device associated with data structure  400 . Additionally, data structure  400  may include first and second pointers, fields  404  and  406 , respectively, pointing to corresponding memory spaces associated with the peripheral device. Additional registers  408  may be included in data structure  400  to contain additional information associated with the corresponding peripheral device. Such additional data may include, for example, a category of peripheral device to which the corresponding device belongs. 
     In step  211 , the RTF builds an interrupt vector table (IVT) which maps interrupt numbers to the data structures built in step  210 . An exemplary IVT  500  is illustrated in FIG.  5 . IVT  500  includes a plurality of entries  502 . Each entry contains an address (pointer) to one of the data structures built in step  210 . The RTF uses the INUM to index into IVT  500 . The data structure addresses in entries  502  are associated with the corresponding INUM by the RTF via the interrupt map passed to the RTF in step  208 . IVT  500  remains in the RTF portion of RAM  114  for the life of the boot. IVT  500  allows the RTF to vector directly to a device data structure based on the device&#39;s INUM, provided by the OS when an interrupt occurs. This will be described further below. 
     As previously described, one or more memory spaces may be associated with each peripheral device to receive data and control information for that device. This may be further understood by referring now to FIG. 6 illustrating a memory (register) space  600  in accordance with an embodiment of the present invention. Memory space  600  includes a plurality, m+1, of memory locations,  602 ,  604 ,  606 , through  608 . A first memory location,  602 , is pointed to by one of pointer  1  and pointer  2  contained in registers  404  and  406 , respectively, of data structure  300 , FIG.  3 . Memory space  600  is illustrated as being pointed to by pointer  2 . However, it would be understood by an artisan of ordinary skill that, alternatively, memory space  600  may be pointed to by pointer  1  in data structure  400 . 
     Memory location  606 , at a preselected offset, l, constitutes an interrupt register. The RTF may use the preselected offset to vector directly to interrupt register  606 . In an embodiment of the present invention, the RTF handles the peripheral device interrupts, and in such an embodiment interrupt register  606  contains information pertaining to the interrupt. This information may, for example, indicate the type of fault that generated the interrupt. Exemplary faults may include overvoltage and undervoltage conditions, or an overtemperature condition. It would be understood by one of ordinary skill in the art that these conditions are illustrative only, and other hardware fault conditions are within the spirit and scope of the present invention. 
     Returning again to FIG. 2, interrupt source isolation using the map tables generated in step  206  and the data structures built in step  210  may be further understood. Method  200  loops, in step  212 , until an interrupt is received. An interrupt is initiated when the interrupting device drives (that is, asserts) a physical interrupt over an interrupt line corresponding to one of the INUMs. If an interrupt is received by the CPU, in step  214 , the OS determines the INUM and passes the INUM to the RTF. In step  216 , using the IVT, the RTF vectors to the interrupting device&#39;s data structure, which data structure may, for example, correspond to the data structure  400  illustrated in FIG.  4 . 
     In step  218 , the register space address in the interrupting device&#39;s data structure is accessed by the RTF. The RTF uses the address to vector to the interrupting devices interrupt register, in step  220 , and in step  222  the RTF retrieves the interrupt information contained in the interrupt register and handles the interrupt. The RTF may, for example, generate an interrupt log and reset the interrupt. It would be understood by an artisan of ordinary skill that particular embodiments of the interrupt handling procedures are device and system configuration specific, and, the aforementioned examples are illustrative only. Other interrupt handling procedures are within the spirit and scope of the present invention, which does not depend on particular interrupt handling procedures for its implementation. After handling the interrupt, the RTF returns to the OS. 
     The present invention allows the operating system to go directly to the interrupting device in order to service the device&#39;s interrupt. During the boot process, the boot firmware binds each physical interrupt to a unique identifier which is then provided to runtime firmware which uses the mapping to associate an interrupt with the interrupting device as represented within the RTF by a corresponding data structure. Access to the interrupt register for the interrupting device is obtained by accessing the memory space associated with the interrupting device via an interrupt vector table generated by the RTF, whereby the RTF can directly vector to the memory space. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.