drivers/platform/chrome/cros_ec_lpc_reg.c

   1 /*
   2  * cros_ec_lpc_reg - LPC access to the Chrome OS Embedded Controller
   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/io.h>
  25 #include <linux/mfd/cros_ec.h>
  26 #include <linux/mfd/cros_ec_commands.h>
  27 #include <linux/mfd/cros_ec_lpc_mec.h>
  28
  29 static u8 lpc_read_bytes(unsigned int offset, unsigned int length, u8 *dest)
  30 {
  31         int i;
  32         int sum = 0;
  33
  34         for (i = 0; i < length; ++i) {
  35                 dest[i] = inb(offset + i);
  36                 sum += dest[i];
  37         }
  38
  39         /* Return checksum of all bytes read */
  40         return sum;
  41 }
  42
  43 static u8 lpc_write_bytes(unsigned int offset, unsigned int length, u8 *msg)
  44 {
  45         int i;
  46         int sum = 0;
  47
  48         for (i = 0; i < length; ++i) {
  49                 outb(msg[i], offset + i);
  50                 sum += msg[i];
  51         }
  52
  53         /* Return checksum of all bytes written */
  54         return sum;
  55 }
  56
  57 #ifdef CONFIG_CROS_EC_LPC_MEC
  58
  59 u8 cros_ec_lpc_read_bytes(unsigned int offset, unsigned int length, u8 *dest)
  60 {
  61         if (length == 0)
  62                 return 0;
  63
  64         /* Access desired range through EMI interface */
  65         if (offset >= MEC_EMI_RANGE_START && offset <= MEC_EMI_RANGE_END) {
  66                 /* Ensure we don't straddle EMI region */
  67                 if (WARN_ON(offset + length - 1 > MEC_EMI_RANGE_END))
  68                         return 0;
  69
  70                 return cros_ec_lpc_io_bytes_mec(MEC_IO_READ, offset, length,
  71                                                 dest);
  72         }
  73
  74         if (WARN_ON(offset + length > MEC_EMI_RANGE_START &&
  75                     offset < MEC_EMI_RANGE_START))
  76                 return 0;
  77
  78         return lpc_read_bytes(offset, length, dest);
  79 }
  80
  81 u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length, u8 *msg)
  82 {
  83         if (length == 0)
  84                 return 0;
  85
  86         /* Access desired range through EMI interface */
  87         if (offset >= MEC_EMI_RANGE_START && offset <= MEC_EMI_RANGE_END) {
  88                 /* Ensure we don't straddle EMI region */
  89                 if (WARN_ON(offset + length - 1 > MEC_EMI_RANGE_END))
  90                         return 0;
  91
  92                 return cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, offset, length,
  93                                                 msg);
  94         }
  95
  96         if (WARN_ON(offset + length > MEC_EMI_RANGE_START &&
  97                     offset < MEC_EMI_RANGE_START))
  98                 return 0;
  99
 100         return lpc_write_bytes(offset, length, msg);
 101 }
 102
 103 void cros_ec_lpc_reg_init(void)
 104 {
 105         cros_ec_lpc_mec_init();
 106 }
 107
 108 void cros_ec_lpc_reg_destroy(void)
 109 {
 110         cros_ec_lpc_mec_destroy();
 111 }
 112
 113 #else /* CONFIG_CROS_EC_LPC_MEC */
 114
 115 u8 cros_ec_lpc_read_bytes(unsigned int offset, unsigned int length, u8 *dest)
 116 {
 117         return lpc_read_bytes(offset, length, dest);
 118 }
 119
 120 u8 cros_ec_lpc_write_bytes(unsigned int offset, unsigned int length, u8 *msg)
 121 {
 122         return lpc_write_bytes(offset, length, msg);
 123 }
 124
 125 void cros_ec_lpc_reg_init(void)
 126 {
 127 }
 128
 129 void cros_ec_lpc_reg_destroy(void)
 130 {
 131 }
 132
 133 #endif /* CONFIG_CROS_EC_LPC_MEC */