1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * Copyright (c) 2001, 2003 Maciej W. Rozycki
4 *
5 * DEC MS02-NV (54-20948-01) battery backed-up NVRAM module for
6 * DECstation/DECsystem 5000/2x0 and DECsystem 5900 and 5900/260
7 * systems.
8 */
9
10 #include <linux/ioport.h>
11 #include <linux/mtd/mtd.h>
12
13 /*
14 * Addresses are decoded as follows:
15 *
16 * 0x000000 - 0x3fffff SRAM
17 * 0x400000 - 0x7fffff CSR
18 *
19 * Within the SRAM area the following ranges are forced by the system
20 * firmware:
21 *
22 * 0x000000 - 0x0003ff diagnostic area, destroyed upon a reboot
23 * 0x000400 - ENDofRAM storage area, available to operating systems
24 *
25 * but we can't really use the available area right from 0x000400 as
26 * the first word is used by the firmware as a status flag passed
27 * from an operating system. If anything but the valid data magic
28 * ID value is found, the firmware considers the SRAM clean, i.e.
29 * containing no valid data, and disables the battery resulting in
30 * data being erased as soon as power is switched off. So the choice
31 * for the start address of the user-available is 0x001000 which is
32 * nicely page aligned. The area between 0x000404 and 0x000fff may
33 * be used by the driver for own needs.
34 *
35 * The diagnostic area defines two status words to be read by an
36 * operating system, a magic ID to distinguish a MS02-NV board from
37 * anything else and a status information providing results of tests
38 * as well as the size of SRAM available, which can be 1MiB or 2MiB
39 * (that's what the firmware handles; no idea if 2MiB modules ever
40 * existed).
41 *
42 * The firmware only handles the MS02-NV board if installed in the
43 * last (15th) slot, so for any other location the status information
44 * stored in the SRAM cannot be relied upon. But from the hardware
45 * point of view there is no problem using up to 14 such boards in a
46 * system -- only the 1st slot needs to be filled with a DRAM module.
47 * The MS02-NV board is ECC-protected, like other MS02 memory boards.
48 *
49 * The state of the battery as provided by the CSR is reflected on
50 * the two onboard LEDs. When facing the battery side of the board,
51 * with the LEDs at the top left and the battery at the bottom right
52 * (i.e. looking from the back side of the system box), their meaning
53 * is as follows (the system has to be powered on):
54 *
55 * left LED battery disable status: lit = enabled
56 * right LED battery condition status: lit = OK
57 */
58
59 /* MS02-NV iomem register offsets. */
60 #define MS02NV_CSR 0x400000 /* control & status register */
61
62 /* MS02-NV CSR status bits. */
63 #define MS02NV_CSR_BATT_OK 0x01 /* battery OK */
64 #define MS02NV_CSR_BATT_OFF 0x02 /* battery disabled */
65
66
67 /* MS02-NV memory offsets. */
68 #define MS02NV_DIAG 0x0003f8 /* diagnostic status */
69 #define MS02NV_MAGIC 0x0003fc /* MS02-NV magic ID */
70 #define MS02NV_VALID 0x000400 /* valid data magic ID */
71 #define MS02NV_RAM 0x001000 /* user-exposed RAM start */
72
73 /* MS02-NV diagnostic status bits. */
74 #define MS02NV_DIAG_TEST 0x01 /* SRAM test done (?) */
75 #define MS02NV_DIAG_RO 0x02 /* SRAM r/o test done */
76 #define MS02NV_DIAG_RW 0x04 /* SRAM r/w test done */
77 #define MS02NV_DIAG_FAIL 0x08 /* SRAM test failed */
78 #define MS02NV_DIAG_SIZE_MASK 0xf0 /* SRAM size mask */
79 #define MS02NV_DIAG_SIZE_SHIFT 0x10 /* SRAM size shift (left) */
80
81 /* MS02-NV general constants. */
82 #define MS02NV_ID 0x03021966 /* MS02-NV magic ID value */
83 #define MS02NV_VALID_ID 0xbd100248 /* valid data magic ID value */
84 #define MS02NV_SLOT_SIZE 0x800000 /* size of the address space
85 decoded by the module */
86
87
88 typedef volatile u32 ms02nv_uint;
89
90 struct ms02nv_private {
91 struct mtd_info *next;
92 struct {
93 struct resource *module;
94 struct resource *diag_ram;
95 struct resource *user_ram;
96 struct resource *csr;
97 } resource;
98 u_char *addr;
99 size_t size;
100 u_char *uaddr;
101 };