Geode™ CS4210
4.4.4 Autonomous CSR Resources
The CS4210 implements a number of autonomous CSR
resources. In particular the 1394 compare-swap bus man-
agement registers are implemented in hardware, as is the
config ROM header, the Bus_Info_Block and access to the
first 1 KB of the configuration ROM. The DMA units handle
external 1394 bus requests to these resources automati-
cally. The serial bus registers shown in Table 4-12 manage
this function for the local host. 1394 requires certain 1394
bus management resource registers be accessible only via
“quadlet read” and “quadlet lock” (compare-and-swap)
transactions, otherwise ack_type_error is sent. These spe-
cial bus management resource registers are implemented
internal to the CS4210 to allow atomic compare-and-swap
access from either the host system or from the 1394 bus.
When these serial bus management resource registers are
accessed from the 1394 bus, the atomic compare-and-
swap transaction is autonomous, without software interven-
tion. If ack_complete is not received to end the transaction
for the generated lock response, IntEvent.lockRespErr
(refer to Table 4-26 on page 70) is triggered. To access
these bus management resource registers from the host,
the registers shown in Table 4-13 are used. To access
these bus management resource registers from the host
bus, first load the CSRReadData register with the new data
value to be loaded into the appropriate resource. Then load
the CSRCompareData register with the expected value.
Finally, write the CSRControl register with the selector
value of the resource. A write to the CSRControl register
initiates a compare-and-swap operation on the selected
resource. When the compare-and-swap operation is com-
plete, the CSRControl register csrDone bit is set, and the
CSRReadData register contains the value of the selected
resource prior to the host initiated compare-and-swap
operation. Note that an arbitrary update of these resources
cannot be done. Only compare-and-swap operations can
be used to modify the contents of these internal resource
registers.
Table 4-12. Serial Bus Registers
CSR Address
FFFF_F000_021Ch
FFFF_F000_0220h
FFFF_F000_0224h
FFFF_F000_0228h
csrSel Bits
(BAR0+Offset 14h[1:0]
00
01
10
11
Description
BUS_MANAGER_ID
BANDWIDTH_AVAILABLE
CHANNELS_AVAILABLE_HI
CHANNELS_AVAILABLE_LO
1394-1995
Section #
8.3.2.3.6
8.3.2.3.7
8.3.2.3.8
8.3.2.3.8
Reset (Hardware or
Bus Reset)
03Fh
1333h
FFFF_FFFFh
FFFF_FFFFh
Table 4-13. CSR Registers
Bit
BAR0+Offset 0Ch
31:0
BAR0+Offset 10h
31:0
csrCompare
RW
csrData
RWU
Name
Access
Reset
Description
CSRReadData Register
Undef
Control/Status Register Read Data:
At start of operation, the data to be
stored if the compare is successful.
CSRCompareData Register
Undef
Control/Status Register Compare:
The data to be compared with the
existing value of the CSR resource.
BAR0+Offset 14h
31
30:2
1:0
csrDone
RSVD
csrSel
RU
--
RW
1
0
CSRControl Register
Control/Status Register Done:
This bit is set when a compare-swap oper-
ation is completed. It is reset whenever this register is written.
Reserved
Control/Status Register Resource Selection:
00 = BUS_MANAGER_ID
01 = BANDWIDTH_AVAILABLE
10 = CHANNELS_AVAILABLE_HI
11 = CHANNELS_AVAILABLE_LO
Undef
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