Limit maximal tranfer rate to 20MHz

[Ralf Messerer]

Hi
I have an Adaptec AHA-294X Ultra with an old external shelf
from digital (DEC BA356) with 3 Ultra wide disk (40MHz) and 4 fast
wide disk (20MHz). The external shelf is spezified for maximum
20MHz transfer frequency. So I configured the maximum tranfer rate
of the 3 Ultra wide disks with the Adaptec controller BIOS to 
40,32, 26.8 and 20 MHz. (What I need is 20MHz because of the shelfs limitation)

Now my problem:
When I switch to 40, 32 and 26.8MHz the Kernel will show me
the corrcet maximum transfer rate of 40, 32 and 26.8 MHz. But
when I try to switch to 20MHz the kernel shows 10MHz tranfer rate,
but it must be 20MHz. I think that something is translated wrong.

I use linux kernel version 2.2.15 with the normal device driver.
-------------------------------
cat /etc/proc/scsi/aix7xxx/0 :


Adaptec AIC7xxx driver version: 5.1.28/3.2.4
Compile Options:
  TCQ Enabled By Default : Enabled
  AIC7XXX_PROC_STATS     : Enabled
  AIC7XXX_RESET_DELAY    : 5

Adapter Configuration:
           SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
                           Ultra Wide Controller at PCI 0/10/0
    PCI MMAPed I/O Base: 0xe0000000
 Adapter SEEPROM Config: SEEPROM found and used.
      Adaptec SCSI BIOS: Enabled
                    IRQ: 10
                   SCBs: Active 0, Max Active 24,
                         Allocated 60, HW 16, Page 255
             Interrupts: 516822
      BIOS Control Word: 0x1816
   Adapter Control Word: 0x005e
   Extended Translation: Disabled
Disconnect Enable Flags: 0xffff
     Ultra Enable Flags: 0x0019
 Tag Queue Enable Flags: 0x007f
Ordered Queue Tag Flags: 0x007f
Default Tag Queue Depth: 8
    Tagged Queue By Device array for aic7xxx host instance 0:
      {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
    Actual queue depth per device for aic7xxx host instance 0:
      {8,8,8,8,8,8,8,1,1,1,1,1,1,1,1,1}

Statistics:

(scsi0:0:0:0)
  Device using Wide/Sync transfers at 26.8 MByte/sec, offset 8
  Transinfo settings: current(18/8/1/0), goal(18/8/1/0), user(18/15/1/0)
  Total transfers 286135 (273127 reads and 13008 writes)
             < 2K      2K+     4K+     8K+    16K+    32K+    64K+  
128K+
   Reads:       4       0  148614   45899   40695   18272   19643      
0
  Writes:       0       0    8783    3776     440       9       0      
0


(scsi0:0:1:0)
  Device using Wide/Sync transfers at 20.0 MByte/sec, offset 8
  Transinfo settings: current(25/8/1/0), goal(12/8/1/0), user(12/15/1/0)
  Total transfers 101364 (96621 reads and 4743 writes)
             < 2K      2K+     4K+     8K+    16K+    32K+    64K+  
128K+
   Reads:       3       0   26698   10409   14182   11265   34064      
0
  Writes:       0       0    2787     916      16       1    1023      
0


(scsi0:0:2:0)
  Device using Wide/Sync transfers at 20.0 MByte/sec, offset 8
  Transinfo settings: current(25/8/1/0), goal(12/8/1/0), user(12/15/1/0)
  Total transfers 128990 (126178 reads and 2812 writes)
             < 2K      2K+     4K+     8K+    16K+    32K+    64K+  
128K+
   Reads:       3       0   27120   28305   52337   13994    4419      
0
  Writes:       0       0     662    1110      16       0    1024      
0


(scsi0:0:3:0)
  Device using Wide/Sync transfers at 26.8 MByte/sec, offset 8
  Transinfo settings: current(18/8/1/0), goal(18/8/1/0), user(18/15/1/0)
  Total transfers 2 (2 reads and 0 writes)
             < 2K      2K+     4K+     8K+    16K+    32K+    64K+  
128K+
   Reads:       2       0       0       0       0       0       0      
0
  Writes:       0       0       0       0       0       0       0      
0


(scsi0:0:4:0)
  Device using Wide/Sync transfers at 26.8 MByte/sec, offset 8
  Transinfo settings: current(18/8/1/0), goal(18/8/1/0), user(18/15/1/0)
  Total transfers 2 (2 reads and 0 writes)
             < 2K      2K+     4K+     8K+    16K+    32K+    64K+  
128K+
   Reads:       2       0       0       0       0       0       0      
0
  Writes:       0       0       0       0       0       0       0      
0


(scsi0:0:5:0)
  Device using Wide/Sync transfers at 20.0 MByte/sec, offset 8
  Transinfo settings: current(25/8/1/0), goal(12/8/1/0), user(12/15/1/0)
  Total transfers 2 (2 reads and 0 writes)
             < 2K      2K+     4K+     8K+    16K+    32K+    64K+  
128K+
   Reads:       2       0       0       0       0       0       0      
0
  Writes:       0       0       0       0       0       0       0      
0


(scsi0:0:6:0)
  Device using Wide/Sync transfers at 20.0 MByte/sec, offset 8
  Transinfo settings: current(25/8/1/0), goal(12/8/1/0), user(12/15/1/0)
  Total transfers 2 (2 reads and 0 writes)
             < 2K      2K+     4K+     8K+    16K+    32K+    64K+  
128K+
   Reads:       2       0       0       0       0       0       0      
0
  Writes:       0       0       0       0       0       0       0      
0



-- 
Ralf Messerer		email: ralf at messerer.com
Gumpisbüelstr. 50	phone:	+41  1 820 38 88
CH-8600 Dübendorf		+41 79 234 24 77


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