1 // SPDX-License-Identifier: GPL-2.0
2 // LPC variant I/O for Microchip EC
3 //
4 // Copyright (C) 2016 Google, Inc
5
6 #include <linux/delay.h>
7 #include <linux/io.h>
8 #include <linux/mutex.h>
9 #include <linux/types.h>
10
11 #include "cros_ec_lpc_mec.h"
12
13 /*
14 * This mutex must be held while accessing the EMI unit. We can't rely on the
15 * EC mutex because memmap data may be accessed without it being held.
16 */
17 static DEFINE_MUTEX(io_mutex);
18 static u16 mec_emi_base, mec_emi_end;
19
20 /**
21 * cros_ec_lpc_mec_emi_write_address() - Initialize EMI at a given address.
22 *
23 * @addr: Starting read / write address
24 * @access_type: Type of access, typically 32-bit auto-increment
25 */
cros_ec_lpc_mec_emi_write_address(u16 addr,enum cros_ec_lpc_mec_emi_access_mode access_type)26 static void cros_ec_lpc_mec_emi_write_address(u16 addr,
27 enum cros_ec_lpc_mec_emi_access_mode access_type)
28 {
29 outb((addr & 0xfc) | access_type, MEC_EMI_EC_ADDRESS_B0(mec_emi_base));
30 outb((addr >> 8) & 0x7f, MEC_EMI_EC_ADDRESS_B1(mec_emi_base));
31 }
32
33 /**
34 * cros_ec_lpc_mec_in_range() - Determine if addresses are in MEC EMI range.
35 *
36 * @offset: Address offset
37 * @length: Number of bytes to check
38 *
39 * Return: 1 if in range, 0 if not, and -EINVAL on failure
40 * such as the mec range not being initialized
41 */
cros_ec_lpc_mec_in_range(unsigned int offset,unsigned int length)42 int cros_ec_lpc_mec_in_range(unsigned int offset, unsigned int length)
43 {
44 if (length == 0)
45 return -EINVAL;
46
47 if (WARN_ON(mec_emi_base == 0 || mec_emi_end == 0))
48 return -EINVAL;
49
50 if (offset >= mec_emi_base && offset < mec_emi_end) {
51 if (WARN_ON(offset + length - 1 >= mec_emi_end))
52 return -EINVAL;
53 return 1;
54 }
55
56 if (WARN_ON(offset + length > mec_emi_base && offset < mec_emi_end))
57 return -EINVAL;
58
59 return 0;
60 }
61
62 /**
63 * cros_ec_lpc_io_bytes_mec() - Read / write bytes to MEC EMI port.
64 *
65 * @io_type: MEC_IO_READ or MEC_IO_WRITE, depending on request
66 * @offset: Base read / write address
67 * @length: Number of bytes to read / write
68 * @buf: Destination / source buffer
69 *
70 * Return: 8-bit checksum of all bytes read / written
71 */
cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,unsigned int offset,unsigned int length,u8 * buf)72 u8 cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,
73 unsigned int offset, unsigned int length,
74 u8 *buf)
75 {
76 int i = 0;
77 int io_addr;
78 u8 sum = 0;
79 enum cros_ec_lpc_mec_emi_access_mode access, new_access;
80
81 /* Return checksum of 0 if window is not initialized */
82 WARN_ON(mec_emi_base == 0 || mec_emi_end == 0);
83 if (mec_emi_base == 0 || mec_emi_end == 0)
84 return 0;
85
86 /*
87 * Long access cannot be used on misaligned data since reading B0 loads
88 * the data register and writing B3 flushes.
89 */
90 if (offset & 0x3 || length < 4)
91 access = ACCESS_TYPE_BYTE;
92 else
93 access = ACCESS_TYPE_LONG_AUTO_INCREMENT;
94
95 mutex_lock(&io_mutex);
96
97 /* Initialize I/O at desired address */
98 cros_ec_lpc_mec_emi_write_address(offset, access);
99
100 /* Skip bytes in case of misaligned offset */
101 io_addr = MEC_EMI_EC_DATA_B0(mec_emi_base) + (offset & 0x3);
102 while (i < length) {
103 while (io_addr <= MEC_EMI_EC_DATA_B3(mec_emi_base)) {
104 if (io_type == MEC_IO_READ)
105 buf[i] = inb(io_addr++);
106 else
107 outb(buf[i], io_addr++);
108
109 sum += buf[i++];
110 offset++;
111
112 /* Extra bounds check in case of misaligned length */
113 if (i == length)
114 goto done;
115 }
116
117 /*
118 * Use long auto-increment access except for misaligned write,
119 * since writing B3 triggers the flush.
120 */
121 if (length - i < 4 && io_type == MEC_IO_WRITE)
122 new_access = ACCESS_TYPE_BYTE;
123 else
124 new_access = ACCESS_TYPE_LONG_AUTO_INCREMENT;
125
126 if (new_access != access ||
127 access != ACCESS_TYPE_LONG_AUTO_INCREMENT) {
128 access = new_access;
129 cros_ec_lpc_mec_emi_write_address(offset, access);
130 }
131
132 /* Access [B0, B3] on each loop pass */
133 io_addr = MEC_EMI_EC_DATA_B0(mec_emi_base);
134 }
135
136 done:
137 mutex_unlock(&io_mutex);
138
139 return sum;
140 }
141 EXPORT_SYMBOL(cros_ec_lpc_io_bytes_mec);
142
cros_ec_lpc_mec_init(unsigned int base,unsigned int end)143 void cros_ec_lpc_mec_init(unsigned int base, unsigned int end)
144 {
145 mec_emi_base = base;
146 mec_emi_end = end;
147 }
148 EXPORT_SYMBOL(cros_ec_lpc_mec_init);
149
