1 /*
2  * cros_ec_lpc_mec - LPC variant I/O for Microchip EC
3  *
4  * Copyright (C) 2016 Google, Inc
5  *
6  * This software is licensed under the terms of the GNU General Public
7  * License version 2, as published by the Free Software Foundation, and
8  * may be copied, distributed, and modified under those terms.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  * This driver uses the Chrome OS EC byte-level message-based protocol for
16  * communicating the keyboard state (which keys are pressed) from a keyboard EC
17  * to the AP over some bus (such as i2c, lpc, spi).  The EC does debouncing,
18  * but everything else (including deghosting) is done here.  The main
19  * motivation for this is to keep the EC firmware as simple as possible, since
20  * it cannot be easily upgraded and EC flash/IRAM space is relatively
21  * expensive.
22  */
23 
24 #include <linux/delay.h>
25 #include <linux/io.h>
26 #include <linux/mfd/cros_ec_commands.h>
27 #include <linux/mfd/cros_ec_lpc_mec.h>
28 #include <linux/mutex.h>
29 #include <linux/types.h>
30 
31 /*
32  * This mutex must be held while accessing the EMI unit. We can't rely on the
33  * EC mutex because memmap data may be accessed without it being held.
34  */
35 static struct mutex io_mutex;
36 
37 /*
38  * cros_ec_lpc_mec_emi_write_address
39  *
40  * Initialize EMI read / write at a given address.
41  *
42  * @addr:        Starting read / write address
43  * @access_type: Type of access, typically 32-bit auto-increment
44  */
45 static void cros_ec_lpc_mec_emi_write_address(u16 addr,
46 			enum cros_ec_lpc_mec_emi_access_mode access_type)
47 {
48 	/* Address relative to start of EMI range */
49 	addr -= MEC_EMI_RANGE_START;
50 	outb((addr & 0xfc) | access_type, MEC_EMI_EC_ADDRESS_B0);
51 	outb((addr >> 8) & 0x7f, MEC_EMI_EC_ADDRESS_B1);
52 }
53 
54 /*
55  * cros_ec_lpc_io_bytes_mec - Read / write bytes to MEC EMI port
56  *
57  * @io_type: MEC_IO_READ or MEC_IO_WRITE, depending on request
58  * @offset:  Base read / write address
59  * @length:  Number of bytes to read / write
60  * @buf:     Destination / source buffer
61  *
62  * @return 8-bit checksum of all bytes read / written
63  */
64 u8 cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,
65 			    unsigned int offset, unsigned int length,
66 			    u8 *buf)
67 {
68 	int i = 0;
69 	int io_addr;
70 	u8 sum = 0;
71 	enum cros_ec_lpc_mec_emi_access_mode access, new_access;
72 
73 	/*
74 	 * Long access cannot be used on misaligned data since reading B0 loads
75 	 * the data register and writing B3 flushes.
76 	 */
77 	if (offset & 0x3 || length < 4)
78 		access = ACCESS_TYPE_BYTE;
79 	else
80 		access = ACCESS_TYPE_LONG_AUTO_INCREMENT;
81 
82 	mutex_lock(&io_mutex);
83 
84 	/* Initialize I/O at desired address */
85 	cros_ec_lpc_mec_emi_write_address(offset, access);
86 
87 	/* Skip bytes in case of misaligned offset */
88 	io_addr = MEC_EMI_EC_DATA_B0 + (offset & 0x3);
89 	while (i < length) {
90 		while (io_addr <= MEC_EMI_EC_DATA_B3) {
91 			if (io_type == MEC_IO_READ)
92 				buf[i] = inb(io_addr++);
93 			else
94 				outb(buf[i], io_addr++);
95 
96 			sum += buf[i++];
97 			offset++;
98 
99 			/* Extra bounds check in case of misaligned length */
100 			if (i == length)
101 				goto done;
102 		}
103 
104 		/*
105 		 * Use long auto-increment access except for misaligned write,
106 		 * since writing B3 triggers the flush.
107 		 */
108 		if (length - i < 4 && io_type == MEC_IO_WRITE)
109 			new_access = ACCESS_TYPE_BYTE;
110 		else
111 			new_access = ACCESS_TYPE_LONG_AUTO_INCREMENT;
112 
113 		if (new_access != access ||
114 		    access != ACCESS_TYPE_LONG_AUTO_INCREMENT) {
115 			access = new_access;
116 			cros_ec_lpc_mec_emi_write_address(offset, access);
117 		}
118 
119 		/* Access [B0, B3] on each loop pass */
120 		io_addr = MEC_EMI_EC_DATA_B0;
121 	}
122 
123 done:
124 	mutex_unlock(&io_mutex);
125 
126 	return sum;
127 }
128 EXPORT_SYMBOL(cros_ec_lpc_io_bytes_mec);
129 
130 void cros_ec_lpc_mec_init(void)
131 {
132 	mutex_init(&io_mutex);
133 }
134 EXPORT_SYMBOL(cros_ec_lpc_mec_init);
135 
136 void cros_ec_lpc_mec_destroy(void)
137 {
138 	mutex_destroy(&io_mutex);
139 }
140 EXPORT_SYMBOL(cros_ec_lpc_mec_destroy);
141