drivers/misc/cros_ec_spi.c

   1 /*
   2  * Chromium OS cros_ec driver - SPI interface
   3  *
   4  * Copyright (c) 2012 The Chromium OS Authors.
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 /*
  25  * The Matrix Keyboard Protocol driver handles talking to the keyboard
  26  * controller chip. Mostly this is for keyboard functions, but some other
  27  * things have slipped in, so we provide generic services to talk to the
  28  * KBC.
  29  */
  30
  31 #include <common.h>
  32 #include <cros_ec.h>
  33 #include <spi.h>
  34
  35 /**
  36  * Send a command to a LPC CROS_EC device and return the reply.
  37  *
  38  * The device's internal input/output buffers are used.
  39  *
  40  * @param dev           CROS_EC device
  41  * @param cmd           Command to send (EC_CMD_...)
  42  * @param cmd_version   Version of command to send (EC_VER_...)
  43  * @param dout          Output data (may be NULL If dout_len=0)
  44  * @param dout_len      Size of output data in bytes
  45  * @param dinp          Returns pointer to response data. This will be
  46  *                      untouched unless we return a value > 0.
  47  * @param din_len       Maximum size of response in bytes
  48  * @return number of bytes in response, or -1 on error
  49  */
  50 int cros_ec_spi_command(struct cros_ec_dev *dev, uint8_t cmd, int cmd_version,
  51                      const uint8_t *dout, int dout_len,
  52                      uint8_t **dinp, int din_len)
  53 {
  54         int in_bytes = din_len + 4;     /* status, length, checksum, trailer */
  55         uint8_t *out;
  56         uint8_t *p;
  57         int csum, len;
  58         int rv;
  59
  60         /*
  61          * Sanity-check input size to make sure it plus transaction overhead
  62          * fits in the internal device buffer.
  63          */
  64         if (in_bytes > sizeof(dev->din)) {
  65                 debug("%s: Cannot receive %d bytes\n", __func__, din_len);
  66                 return -1;
  67         }
  68
  69         /* We represent message length as a byte */
  70         if (dout_len > 0xff) {
  71                 debug("%s: Cannot send %d bytes\n", __func__, dout_len);
  72                 return -1;
  73         }
  74
  75         /*
  76          * Clear input buffer so we don't get false hits for MSG_HEADER
  77          */
  78         memset(dev->din, '\0', in_bytes);
  79
  80         if (spi_claim_bus(dev->spi)) {
  81                 debug("%s: Cannot claim SPI bus\n", __func__);
  82                 return -1;
  83         }
  84
  85         out = dev->dout;
  86         out[0] = cmd_version;
  87         out[1] = cmd;
  88         out[2] = (uint8_t)dout_len;
  89         memcpy(out + 3, dout, dout_len);
  90         csum = cros_ec_calc_checksum(out, 3)
  91                + cros_ec_calc_checksum(dout, dout_len);
  92         out[3 + dout_len] = (uint8_t)csum;
  93
  94         /*
  95          * Send output data and receive input data starting such that the
  96          * message body will be dword aligned.
  97          */
  98         p = dev->din + sizeof(int64_t) - 2;
  99         len = dout_len + 4;
 100         cros_ec_dump_data("out", cmd, out, len);
 101         rv = spi_xfer(dev->spi, max(len, in_bytes) * 8, out, p,
 102                       SPI_XFER_BEGIN | SPI_XFER_END);
 103
 104         spi_release_bus(dev->spi);
 105
 106         if (rv) {
 107                 debug("%s: Cannot complete SPI transfer\n", __func__);
 108                 return -1;
 109         }
 110
 111         len = min(p[1], din_len);
 112         cros_ec_dump_data("in", -1, p, len + 3);
 113
 114         /* Response code is first byte of message */
 115         if (p[0] != EC_RES_SUCCESS) {
 116                 printf("%s: Returned status %d\n", __func__, p[0]);
 117                 return -(int)(p[0]);
 118         }
 119
 120         /* Check checksum */
 121         csum = cros_ec_calc_checksum(p, len + 2);
 122         if (csum != p[len + 2]) {
 123                 debug("%s: Invalid checksum rx %#02x, calced %#02x\n", __func__,
 124                       p[2 + len], csum);
 125                 return -1;
 126         }
 127
 128         /* Anything else is the response data */
 129         *dinp = p + 2;
 130
 131         return len;
 132 }
 133
 134 int cros_ec_spi_decode_fdt(struct cros_ec_dev *dev, const void *blob)
 135 {
 136         /* Decode interface-specific FDT params */
 137         dev->max_frequency = fdtdec_get_int(blob, dev->node,
 138                                             "spi-max-frequency", 500000);
 139         dev->cs = fdtdec_get_int(blob, dev->node, "reg", 0);
 140
 141         return 0;
 142 }
 143
 144 /**
 145  * Initialize SPI protocol.
 146  *
 147  * @param dev           CROS_EC device
 148  * @param blob          Device tree blob
 149  * @return 0 if ok, -1 on error
 150  */
 151 int cros_ec_spi_init(struct cros_ec_dev *dev, const void *blob)
 152 {
 153         dev->spi = spi_setup_slave_fdt(blob, dev->parent_node,
 154                                        dev->cs, dev->max_frequency, 0);
 155         if (!dev->spi) {
 156                 debug("%s: Could not setup SPI slave\n", __func__);
 157                 return -1;
 158         }
 159
 160         return 0;
 161 }