1 .. SPDX-License-Identifier: GPL-2.0
3 =======================
4 The 53c700 Driver Notes
5 =======================
10 This driver supports the 53c700 and 53c700-66 chips. It also supports
11 the 53c710 but only in 53c700 emulation mode. It is full featured and
12 does sync (-66 and 710 only), disconnects and tag command queueing.
14 Since the 53c700 must be interfaced to a bus, you need to wrapper the
15 card detector around this driver. For an example, see the
16 NCR_D700.[ch] or lasi700.[ch] files.
18 The comments in the 53c700.[ch] files tell you which parts you need to
19 fill in to get the driver working.
25 A compile time flag is::
27 CONFIG_53C700_LE_ON_BE
29 define if the chipset must be supported in little endian mode on a big
30 endian architecture (used for the 700 on parisc).
33 Using the Chip Core Driver
34 ==========================
36 In order to plumb the 53c700 chip core driver into a working SCSI
37 driver, you need to know three things about the way the chip is wired
38 into your system (or expansion card).
40 1. The clock speed of the SCSI core
41 2. The interrupt line used
42 3. The memory (or io space) location of the 53c700 registers.
44 Optionally, you may also need to know other things, like how to read
45 the SCSI Id from the card bios or whether the chip is wired for
46 differential operation.
48 Usually you can find items 2. and 3. from general spec. documents or
49 even by examining the configuration of a working driver under another
52 The clock speed is usually buried deep in the technical literature.
53 It is required because it is used to set up both the synchronous and
54 asynchronous dividers for the chip. As a general rule of thumb,
55 manufacturers set the clock speed at the lowest possible setting
56 consistent with the best operation of the chip (although some choose
57 to drive it off the CPU or bus clock rather than going to the expense
58 of an extra clock chip). The best operation clock speeds are:
66 Writing Your Glue Driver
67 ========================
69 This will be a standard SCSI driver (I don't know of a good document
70 describing this, just copy from some other driver) with at least a
71 detect and release entry.
73 In the detect routine, you need to allocate a struct
74 NCR_700_Host_Parameters sized memory area and clear it (so that the
75 default values for everything are 0). Then you must fill in the
76 parameters that matter to you (see below), plumb the NCR_700_intr
77 routine into the interrupt line and call NCR_700_detect with the host
78 template and the new parameters as arguments. You should also call
79 the relevant request_*_region function and place the register base
80 address into the 'base' pointer of the host parameters.
82 In the release routine, you must free the NCR_700_Host_Parameters that
83 you allocated, call the corresponding release_*_region and free the
89 In general, you should just plumb the card's interrupt line in with
91 request_irq(irq, NCR_700_intr, <irq flags>, <driver name>, host);
93 where host is the return from the relevant NCR_700_detect() routine.
95 You may also write your own interrupt handling routine which calls
96 NCR_700_intr() directly. However, you should only really do this if
97 you have a card with more than one chip on it and you can read a
98 register to tell which set of chips wants the interrupt.
100 Settable NCR_700_Host_Parameters
101 --------------------------------
103 The following are a list of the user settable parameters:
106 Set to the clock speed of the chip in MHz.
109 Set to the base of the io or mem region for the register set. On 64
110 bit architectures this is only 32 bits wide, so the registers must be
111 mapped into the low 32 bits of memory.
114 Set to the PCI board device. Leave NULL for a non-pci board. This is
115 used for the pci_alloc_consistent() and pci_map_*() functions.
117 dmode_extra: (OPTIONAL, 53c710 only)
118 Extra flags for the DMODE register. These are used to control bus
119 output pins on the 710. The settings should be a combination of
120 DMODE_FC1 and DMODE_FC2. What these pins actually do is entirely up
121 to the board designer. Usually it is safe to ignore this setting.
123 differential: (OPTIONAL)
124 Set to 1 if the chip drives a differential bus.
126 force_le_on_be: (OPTIONAL, only if CONFIG_53C700_LE_ON_BE is set)
127 Set to 1 if the chip is operating in little endian mode on a big
131 Set to 1 if the chip is a 53c710.
133 burst_disable: (OPTIONAL, 53c710 only)
134 Disable 8 byte bursting for DMA transfers.