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 */
 35static 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 */
 45static 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 */
 64u8 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
123done:
124	mutex_unlock(&io_mutex);
125
126	return sum;
127}
128EXPORT_SYMBOL(cros_ec_lpc_io_bytes_mec);
129
130void cros_ec_lpc_mec_init(void)
131{
132	mutex_init(&io_mutex);
133}
134EXPORT_SYMBOL(cros_ec_lpc_mec_init);
135
136void cros_ec_lpc_mec_destroy(void)
137{
138	mutex_destroy(&io_mutex);
139}
140EXPORT_SYMBOL(cros_ec_lpc_mec_destroy);