Method and apparatus to permit external access to internal configuration registers

Abstract

Access to internal configuration registers on a computer system's chipset using an external micro-controller is provided. A SMB configuration read command including a register address may be received from an external micro-controller. Access to an internal bus may be requested from a bus arbiter. If internal bus access is granted, the SMB configuration read command may be forwarded to a device including the identified register address using the internal bus. In response to the SMB configuration read command, configuration register values from the device may be received. The configuration register values may be forwarded to the external micro-controller.

1 . An apparatus comprising: 
 a SMB controller to access PCI configuration registers responsive to a read request from an external micro-controller.    
   
   
       2 . The apparatus of  claim 1 , wherein responsive to the read request the SMB controller to generate an SMB configuration read request including an address for a configuration register to be read.  
   
   
       3 . The apparatus of  claim 1 , further comprising: 
 an internal bus coupled to the SMB controller to deliver PCI configuration register values to the SMB controller in response to the read request from the external micro-controller.    
   
   
       4 . The apparatus of  claim 3 , further comprising: 
 when the internal bus is available, a bus arbiter to grant access to the internal bus in response to a request for internal bus access from the SMB controller.    
   
   
       5 . The apparatus of  claim 4 , further comprising: 
 a configuration register to receive a SMB configuration read request from the SMB controller and to send configuration values to the SMB controller.    
   
   
       6 . A system for accessing peripheral configuration registers, comprising: 
 an external bus interface coupled to an external micro-controller using an external system management bus;    an internal bus; and    a system management bus controller coupled to the external bus interface and the internal bus , wherein responsive to a SMB configuration read command including a configuration register address from the external micro-controller, the controller to send the SMB configuration read command to a configuration register of a peripheral device identified by the configuration register address using the internal bus, and wherein the controller to receive configuration register values for the identified configuration register from the peripheral device in response to the SMB configuration read command and to forward the configuration register values to the external micro-controller.    
   
   
       7 . The system of  claim 6 , further comprising: 
 a peripheral device to receive the SMB configuration read command, retrieve configuration register values in configuration register identified by the configuration register address, forward the configuration register values to the system management controller when the internal bus is available for access.    
   
   
       8 . A method comprising; 
 receiving a SMB configuration read command including a register address from an external micro-controller;    requesting access to an internal bus from a bus arbiter;    if internal bus access is granted, forwarding the SMB configuration read command to a device including register address using the internal bus;    responsive to the SMB configuration read command, receiving configuration register values from the device; and    forwarding the configuration register values to the external micro-controller.    
   
   
       9 . The method of  claim 8 , further comprising: 
 determining by the bus arbiter whether the internal bus is available for access; and    granting access to the internal bus when the internal bus is available.    
   
   
       10 . The method of  claim 8 , further comprising: 
 receiving a request to access the internal bus from the device by the bus arbiter;    determining when the internal bus is available for access by the device; and    granting bus access to the device when the internal bus is available.    
   
   
       11 . The method of  claim 10 , further comprising: 
 receiving the SMB configuration read command at the device;    retrieving configuration register values from a configuration register identified by the register address; and    forwarding the configuration register values when the internal bus is available.    
   
   
       12 . A system management bus controller coupled to an external micro-controller and an internal bus, wherein the system management bus controller provides the external micro-controller access to configuration registers of a plurality of peripheral devices connected to a chipset using the internal bus.  
   
   
       13 . The system management controller of  claim 12 , wherein the system bus controller requests access to the internal bus from a bus arbiter, and when access is granted, the system bus controller sends a SMB configuration read command to at least one of the plurality of peripheral devices.  
   
   
       14 . The system management controller of  claim 13 , wherein the system bus controller receives configuration register values from the at least one of the plurality of peripheral devices and forwards the configuration register values to the external micro-controller.  
   
   
       15 . A machine-readable medium having stored thereon a plurality of executable instructions, the plurality of instructions comprising instructions to: 
 receive a SMB configuration read command including a configuration register address from an external micro-controller;    request access to an internal bus from a bus arbiter;    forward the SMB configuration read command to a configuration register of a peripheral device identified by the configuration register address using the internal bus when bus access is granted;    responsive to the SMB configuration read command, receive configuration register values for the identified configuration register from the peripheral device; and    forward the configuration register values to the external micro-controller.    
   
   
       16 . The machine-readable medium of  claim 15  having stored thereon additional executable instructions, the additional instructions comprising instructions to: 
 determine by the bus arbiter whether the internal bus is available for access; and    granting access to the internal bus when the internal bus is available.    
   
   
       17 . The machine-readable medium of  claim 15  having stored thereon additional executable instructions, the additional instructions comprising instructions to: 
 receive a request to access the internal bus from the peripheral device by the bus arbiter;    determine when the internal bus is available for access by the peripheral device; and    grant bus access to the peripheral device when the internal bus is available.    
   
   
       18 . The machine-readable medium of  claim 17  having stored thereon additional executable instructions, the additional instructions comprising instructions to: 
 receive the SMB configuration read command at the peripheral device;    retrieve configuration register values in configuration register identified by the configuration register address; and    forward the configuration register values when the internal bus is available.