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1 | .. SPDX-License-Identifier: GPL-2.0 |
2 | ||
3 | ======================= | |
4 | The 53c700 Driver Notes | |
5 | ======================= | |
6 | ||
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7 | General Description |
8 | =================== | |
9 | ||
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. | |
13 | ||
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. | |
17 | ||
18 | The comments in the 53c700.[ch] files tell you which parts you need to | |
19 | fill in to get the driver working. | |
20 | ||
21 | ||
22 | Compile Time Flags | |
23 | ================== | |
24 | ||
f7657677 | 25 | A compile time flag is:: |
1da177e4 | 26 | |
f7657677 | 27 | CONFIG_53C700_LE_ON_BE |
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28 | |
29 | define if the chipset must be supported in little endian mode on a big | |
30 | endian architecture (used for the 700 on parisc). | |
31 | ||
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32 | |
33 | Using the Chip Core Driver | |
34 | ========================== | |
35 | ||
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). | |
39 | ||
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. | |
43 | ||
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. | |
47 | ||
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 | |
50 | operating system. | |
51 | ||
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: | |
59 | ||
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60 | ========= ===== |
61 | 53c700 25MHz | |
62 | 53c700-66 50MHz | |
63 | 53c710 40Mhz | |
64 | ========= ===== | |
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65 | |
66 | Writing Your Glue Driver | |
67 | ======================== | |
68 | ||
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. | |
72 | ||
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 | |
f7657677 | 80 | address into the 'base' pointer of the host parameters. |
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81 | |
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 | |
84 | interrupt. | |
85 | ||
86 | Handling Interrupts | |
87 | ------------------- | |
88 | ||
f7657677 | 89 | In general, you should just plumb the card's interrupt line in with |
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90 | |
91 | request_irq(irq, NCR_700_intr, <irq flags>, <driver name>, host); | |
92 | ||
93 | where host is the return from the relevant NCR_700_detect() routine. | |
94 | ||
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. | |
99 | ||
100 | Settable NCR_700_Host_Parameters | |
101 | -------------------------------- | |
102 | ||
103 | The following are a list of the user settable parameters: | |
104 | ||
105 | clock: (MANDATORY) | |
f7657677 | 106 | Set to the clock speed of the chip in MHz. |
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107 | |
108 | base: (MANDATORY) | |
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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. | |
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112 | |
113 | pci_dev: (OPTIONAL) | |
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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. | |
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116 | |
117 | dmode_extra: (OPTIONAL, 53c710 only) | |
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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. | |
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122 | |
123 | differential: (OPTIONAL) | |
f7657677 | 124 | Set to 1 if the chip drives a differential bus. |
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125 | |
126 | force_le_on_be: (OPTIONAL, only if CONFIG_53C700_LE_ON_BE is set) | |
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127 | Set to 1 if the chip is operating in little endian mode on a big |
128 | endian architecture. | |
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129 | |
130 | chip710: (OPTIONAL) | |
f7657677 | 131 | Set to 1 if the chip is a 53c710. |
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132 | |
133 | burst_disable: (OPTIONAL, 53c710 only) | |
f7657677 | 134 | Disable 8 byte bursting for DMA transfers. |