pata_serverworks: disable 64-KB DMA transfers on Broadcom OSB4 IDE Controller
pata_serverworks: disable 64-KB DMA transfers on Broadcom OSB4 IDE Controller

The Broadcom OSB4 IDE Controller (vendor and device IDs: 1166:0211)
does not support 64-KB DMA transfers.
Whenever a 64-KB DMA transfer is attempted,
the transfer fails and messages similar to the following
are written to the console log:

   [ 2431.851125] sr 0:0:0:0: [sr0] Unhandled sense code
   [ 2431.851139] sr 0:0:0:0: [sr0]  Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
   [ 2431.851152] sr 0:0:0:0: [sr0]  Sense Key : Hardware Error [current]
   [ 2431.851166] sr 0:0:0:0: [sr0]  Add. Sense: Logical unit communication time-out
   [ 2431.851182] sr 0:0:0:0: [sr0] CDB: Read(10): 28 00 00 00 76 f4 00 00 40 00
   [ 2431.851210] end_request: I/O error, dev sr0, sector 121808

When the libata and pata_serverworks modules
are recompiled with ATA_DEBUG and ATA_VERBOSE_DEBUG defined in libata.h,
the 64-KB transfer size in the scatter-gather list can be seen
in the console log:

   [ 2664.897267] sr 9:0:0:0: [sr0] Send:
   [ 2664.897274] 0xf63d85e0
   [ 2664.897283] sr 9:0:0:0: [sr0] CDB:
   [ 2664.897288] Read(10): 28 00 00 00 7f b4 00 00 40 00
   [ 2664.897319] buffer = 0xf6d6fbc0, bufflen = 131072, queuecommand 0xf81b7700
   [ 2664.897331] ata_scsi_dump_cdb: CDB (1:0,0,0) 28 00 00 00 7f b4 00 00 40
   [ 2664.897338] ata_scsi_translate: ENTER
   [ 2664.897345] ata_sg_setup: ENTER, ata1
   [ 2664.897356] ata_sg_setup: 3 sg elements mapped
   [ 2664.897364] ata_bmdma_fill_sg: PRD[0] = (0x66FD2000, 0xE000)
   [ 2664.897371] ata_bmdma_fill_sg: PRD[1] = (0x65000000, 0x10000)
   ------------------------------------------------------> =======
   [ 2664.897378] ata_bmdma_fill_sg: PRD[2] = (0x66A10000, 0x2000)
   [ 2664.897386] ata1: ata_dev_select: ENTER, device 0, wait 1
   [ 2664.897422] ata_sff_tf_load: feat 0x1 nsect 0x0 lba 0x0 0x0 0xFC
   [ 2664.897428] ata_sff_tf_load: device 0xA0
   [ 2664.897448] ata_sff_exec_command: ata1: cmd 0xA0
   [ 2664.897457] ata_scsi_translate: EXIT
   [ 2664.897462] leaving scsi_dispatch_cmnd()
   [ 2664.897497] Doing sr request, dev = sr0, block = 0
   [ 2664.897507] sr0 : reading 64/256 512 byte blocks.
   [ 2664.897553] ata_sff_hsm_move: ata1: protocol 7 task_state 1 (dev_stat 0x58)
   [ 2664.897560] atapi_send_cdb: send cdb
   [ 2666.910058] ata_bmdma_port_intr: ata1: host_stat 0x64
   [ 2666.910079] __ata_sff_port_intr: ata1: protocol 7 task_state 3
   [ 2666.910093] ata_sff_hsm_move: ata1: protocol 7 task_state 3 (dev_stat 0x51)
   [ 2666.910101] ata_sff_hsm_move: ata1: protocol 7 task_state 4 (dev_stat 0x51)
   [ 2666.910129] sr 9:0:0:0: [sr0] Done:
   [ 2666.910136] 0xf63d85e0 TIMEOUT

lspci shows that the driver used for the Broadcom OSB4 IDE Controller is
pata_serverworks:

   00:0f.1 IDE interface: Broadcom OSB4 IDE Controller (prog-if 8e [Master SecP SecO PriP])
           Flags: bus master, medium devsel, latency 64
           [virtual] Memory at 000001f0 (32-bit, non-prefetchable) [size=8]
           [virtual] Memory at 000003f0 (type 3, non-prefetchable) [size=1]
           I/O ports at 0170 [size=8]
           I/O ports at 0374 [size=4]
           I/O ports at 1440 [size=16]
           Kernel driver in use: pata_serverworks

The pata_serverworks driver supports five distinct device IDs,
one being the OSB4 and the other four belonging to the CSB series.
The CSB series appears to support 64-KB DMA transfers,
as tests on a machine with an SAI2 motherboard
containing a Broadcom CSB5 IDE Controller (vendor and device IDs: 1166:0212)
showed no problems with 64-KB DMA transfers.

This problem was first discovered when attempting to install openSUSE
from a DVD on a machine with an STL2 motherboard.
Using the pata_serverworks module,
older releases of openSUSE will not install at all due to the timeouts.
Releases of openSUSE prior to 11.3 can be installed by disabling
the pata_serverworks module using the brokenmodules boot parameter,
which causes the serverworks module to be used instead.
Recent releases of openSUSE (12.2 and later) include better error recovery and
will install, though very slowly.
On all openSUSE releases, the problem can be recreated
on a machine containing a Broadcom OSB4 IDE Controller
by mounting an install DVD and running a command similar to the following:

   find /mnt -type f -print | xargs cat > /dev/null

The patch below corrects the problem.
Similar to the other ATA drivers that do not support 64-KB DMA transfers,
the patch changes the ata_port_operations qc_prep vector to point to a routine
that breaks any 64-KB segment into two 32-KB segments and
changes the scsi_host_template sg_tablesize element to reduce by half
the number of scatter/gather elements allowed.
These two changes affect only the OSB4.

Signed-off-by: Scott Carter <edf310b976c2449a5081a20cf8f4b2e6dc9e64fd@funsoft.com>
Signed-off-by: Tejun Heo <546b05909706652891a87f7bfe385ae147f61f91@kernel.org>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org

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