Multiple descriptor queues
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Multiple Descriptor-Queues. We discover the role played by the MULR-bit (bit #18) in the Transmit Control Register. Our ‘igbe.c’ tool. We wrote this module as an aid for doing ‘debugging’ of our device-driver routines

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Multiple Descriptor-Queues

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Multiple descriptor queues

Multiple Descriptor-Queues

We discover the role played by the MULR-bit (bit #18) in the Transmit Control Register


Our igbe c tool

Our ‘igbe.c’ tool

  • We wrote this module as an aid for doing ‘debugging’ of our device-driver routines

  • It creates a pseudo-file that will show us the current values in significant registers

  • Already it has disclosed a ‘problem’ with our previous ‘txburst.c’ demonstation

  • Driver wrote 0x0103F0F8 into TCTL, but ‘/proc/igbe’ shows 0x1103F0F8 in TCTL


Screenshot

Screenshot


Multiple descriptor queues

Transmit Control (0x0400)

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16

R

=0

R

=0

R

=0

MULR

TXCSCMT

UNO

RTX

RTLC

R

=0

SW

XOFF

COLD (upper 6-bits)

(COLLISION DISTANCE)

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

COLD (lower 4-bits)

(COLLISION DISTANCE)

CT

(COLLISION THRESHOLD)

0

ASDV

SPEED

I

L

O

S

S

L

U

TBI

mode

P

S

P

R

=0

0 0

E

N

R

=0

EN = Transmit EnableSWXOFF = Software XOFF Transmission

PSP = Pad Short PacketsRLTC = Retransmit on Late Collision

CT = Collision Threshold (=0xF)UNORTX = Underrun No Re-Transmit

COLD = Collision Distance (=0x3F)TXCSCMT = TxDescriptor Minimum Threshold

MULR = Multiple Request Support

We used 0x0103F0F8 in TCTL to setup the ‘transmit engine’ before enabling it

82573L


Twin descriptor queues

Twin Descriptor Queues

TDBA0

Tx Desc Queue0

TDBA1

Tx Desc Queue1

TDH1

TDH0

TDT0

TDT1

= descriptor is ‘owned’ by device-driver

= descriptor is ‘owned’ by network-controller


Tx arbitration count 0x3840

Tx Arbitration Count (0x3840)

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16

RESERVED

=0

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

RESERVED

=0

0

E

N

A

B

L

E

RATIO

I

L

O

S

R

=0

S

L

U

COUNT

(must not be 0)

TBI

mode

0 0

ENABLE = Descriptor Enable

(Always set to1)

RATIO = Compensation Ratio

(00=1/1, 01=1/2, 10=1/4, 11=1/8)

82573L


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