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Documentation / scsi / aha152x.txt




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Based on kernel version 3.13. Page generated on 2014-01-20 22:04 EST.

1	$Id: README.aha152x,v 1.2 1999/12/25 15:32:30 fischer Exp fischer $
2	Adaptec AHA-1520/1522 SCSI driver for Linux (aha152x)
3	
4	Copyright 1993-1999 Jürgen Fischer <fischer@norbit.de>
5	TC1550 patches by Luuk van Dijk (ldz@xs4all.nl)
6	
7	
8	In Revision 2 the driver was modified a lot (especially the
9	bottom-half handler complete()).
10	
11	The driver is much cleaner now, has support for the new
12	error handling code in 2.3, produced less cpu load (much
13	less polling loops), has slightly higher throughput (at
14	least on my ancient test box; a i486/33Mhz/20MB).
15	
16	
17	CONFIGURATION ARGUMENTS:
18	
19	IOPORT        base io address                           (0x340/0x140)
20	IRQ           interrupt level                           (9-12; default 11)
21	SCSI_ID       scsi id of controller                     (0-7; default 7)
22	RECONNECT     allow targets to disconnect from the bus  (0/1; default 1 [on])
23	PARITY        enable parity checking                    (0/1; default 1 [on])
24	SYNCHRONOUS   enable synchronous transfers              (0/1; default 1 [on])
25	DELAY:        bus reset delay                           (default 100)
26	EXT_TRANS:    enable extended translation               (0/1: default 0 [off])
27	              (see NOTES)
28	
29	COMPILE TIME CONFIGURATION (go into AHA152X in drivers/scsi/Makefile):
30	
31	-DAUTOCONF
32	 use configuration the controller reports (AHA-152x only)
33	
34	-DSKIP_BIOSTEST
35	 Don't test for BIOS signature (AHA-1510 or disabled BIOS)
36	
37	-DSETUP0="{ IOPORT, IRQ, SCSI_ID, RECONNECT, PARITY, SYNCHRONOUS, DELAY, EXT_TRANS }"
38	 override for the first controller 
39	
40	-DSETUP1="{ IOPORT, IRQ, SCSI_ID, RECONNECT, PARITY, SYNCHRONOUS, DELAY, EXT_TRANS }"
41	 override for the second controller
42	
43	-DAHA152X_DEBUG
44	 enable debugging output
45	
46	-DAHA152X_STAT
47	 enable some statistics
48	
49	
50	LILO COMMAND LINE OPTIONS:
51	
52	aha152x=<IOPORT>[,<IRQ>[,<SCSI-ID>[,<RECONNECT>[,<PARITY>[,<SYNCHRONOUS>[,<DELAY> [,<EXT_TRANS]]]]]]]
53	
54	 The normal configuration can be overridden by specifying a command line.
55	 When you do this, the BIOS test is skipped. Entered values have to be
56	 valid (known).  Don't use values that aren't supported under normal
57	 operation.  If you think that you need other values: contact me.
58	 For two controllers use the aha152x statement twice.
59	
60	
61	SYMBOLS FOR MODULE CONFIGURATION:
62	
63	Choose from 2 alternatives:
64	
65	1. specify everything (old)
66	
67	aha152x=IOPORT,IRQ,SCSI_ID,RECONNECT,PARITY,SYNCHRONOUS,DELAY,EXT_TRANS
68	  configuration override for first controller
69	
70	
71	aha152x1=IOPORT,IRQ,SCSI_ID,RECONNECT,PARITY,SYNCHRONOUS,DELAY,EXT_TRANS
72	  configuration override for second controller
73	
74	2. specify only what you need to (irq or io is required; new)
75	
76	io=IOPORT0[,IOPORT1]
77	  IOPORT for first and second controller
78	
79	irq=IRQ0[,IRQ1]
80	  IRQ for first and second controller
81	
82	scsiid=SCSIID0[,SCSIID1]
83	  SCSIID for first and second controller
84	
85	reconnect=RECONNECT0[,RECONNECT1]
86	  allow targets to disconnect for first and second controller
87	
88	parity=PAR0[PAR1]
89	  use parity for first and second controller
90	
91	sync=SYNCHRONOUS0[,SYNCHRONOUS1]
92	  enable synchronous transfers for first and second controller
93	
94	delay=DELAY0[,DELAY1]
95	  reset DELAY for first and second controller
96	
97	exttrans=EXTTRANS0[,EXTTRANS1]
98	  enable extended translation for first and second controller
99	
100	
101	If you use both alternatives the first will be taken.
102	
103	
104	NOTES ON EXT_TRANS: 
105	
106	SCSI uses block numbers to address blocks/sectors on a device.
107	The BIOS uses a cylinder/head/sector addressing scheme (C/H/S)
108	scheme instead.  DOS expects a BIOS or driver that understands this
109	C/H/S addressing.
110	
111	The number of cylinders/heads/sectors is called geometry and is required
112	as base for requests in C/H/S addressing.  SCSI only knows about the
113	total capacity of disks in blocks (sectors).
114	
115	Therefore the SCSI BIOS/DOS driver has to calculate a logical/virtual
116	geometry just to be able to support that addressing scheme.  The geometry
117	returned by the SCSI BIOS is a pure calculation and has nothing to
118	do with the real/physical geometry of the disk (which is usually
119	irrelevant anyway).
120	
121	Basically this has no impact at all on Linux, because it also uses block
122	instead of C/H/S addressing.  Unfortunately C/H/S addressing is also used
123	in the partition table and therefore every operating system has to know
124	the right geometry to be able to interpret it.
125	
126	Moreover there are certain limitations to the C/H/S addressing scheme,
127	namely the address space is limited to up to 255 heads, up to 63 sectors
128	and a maximum of 1023 cylinders.
129	
130	The AHA-1522 BIOS calculates the geometry by fixing the number of heads
131	to 64, the number of sectors to 32 and by calculating the number of
132	cylinders by dividing the capacity reported by the disk by 64*32 (1 MB).
133	This is considered to be the default translation.
134	
135	With respect to the limit of 1023 cylinders using C/H/S you can only
136	address the first GB of your disk in the partition table.  Therefore
137	BIOSes of some newer controllers based on the AIC-6260/6360 support
138	extended translation.  This means that the BIOS uses 255 for heads,
139	63 for sectors and then divides the capacity of the disk by 255*63
140	(about 8 MB), as soon it sees a disk greater than 1 GB.  That results
141	in a maximum of about 8 GB addressable diskspace in the partition table
142	(but there are already bigger disks out there today).
143	
144	To make it even more complicated the translation mode might/might
145	not be configurable in certain BIOS setups.
146	
147	This driver does some more or less failsafe guessing to get the
148	geometry right in most cases:
149	
150	- for disks<1GB: use default translation (C/32/64)
151	
152	- for disks>1GB:
153	  - take current geometry from the partition table
154	    (using scsicam_bios_param and accept only `valid' geometries,
155	    ie. either (C/32/64) or (C/63/255)).  This can be extended translation
156	    even if it's not enabled in the driver.
157	
158	  - if that fails, take extended translation if enabled by override,
159	    kernel or module parameter, otherwise take default translation and
160	    ask the user for verification.  This might on not yet partitioned
161	    disks.
162	
163	
164	REFERENCES USED:
165	
166	 "AIC-6260 SCSI Chip Specification", Adaptec Corporation.
167	
168	 "SCSI COMPUTER SYSTEM INTERFACE - 2 (SCSI-2)", X3T9.2/86-109 rev. 10h
169	
170	 "Writing a SCSI device driver for Linux", Rik Faith (faith@cs.unc.edu)
171	
172	 "Kernel Hacker's Guide", Michael K. Johnson (johnsonm@sunsite.unc.edu)
173	
174	 "Adaptec 1520/1522 User's Guide", Adaptec Corporation.
175	
176	 Michael K. Johnson (johnsonm@sunsite.unc.edu)
177	
178	 Drew Eckhardt (drew@cs.colorado.edu)
179	
180	 Eric Youngdale (eric@andante.org) 
181	
182	 special thanks to Eric Youngdale for the free(!) supplying the
183	 documentation on the chip.
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