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  *
   6  * SPDX-License-Identifier:     GPL-2.0+
   7  */
   8
   9 /*
  10  * The Matrix Keyboard Protocol driver handles talking to the keyboard
  11  * controller chip. Mostly this is for keyboard functions, but some other
  12  * things have slipped in, so we provide generic services to talk to the
  13  * KBC.
  14  */
  15
  16 #include <common.h>
  17 #include <cros_ec.h>
  18 #include <spi.h>
  19
  20 /**
  21  * Send a command to a LPC CROS_EC device and return the reply.
  22  *
  23  * The device's internal input/output buffers are used.
  24  *
  25  * @param dev           CROS_EC device
  26  * @param cmd           Command to send (EC_CMD_...)
  27  * @param cmd_version   Version of command to send (EC_VER_...)
  28  * @param dout          Output data (may be NULL If dout_len=0)
  29  * @param dout_len      Size of output data in bytes
  30  * @param dinp          Returns pointer to response data. This will be
  31  *                      untouched unless we return a value > 0.
  32  * @param din_len       Maximum size of response in bytes
  33  * @return number of bytes in response, or -1 on error
  34  */
  35 int cros_ec_spi_command(struct cros_ec_dev *dev, uint8_t cmd, int cmd_version,
  36                      const uint8_t *dout, int dout_len,
  37                      uint8_t **dinp, int din_len)
  38 {
  39         int in_bytes = din_len + 4;     /* status, length, checksum, trailer */
  40         uint8_t *out;
  41         uint8_t *p;
  42         int csum, len;
  43         int rv;
  44
  45         /*
  46          * Sanity-check input size to make sure it plus transaction overhead
  47          * fits in the internal device buffer.
  48          */
  49         if (in_bytes > sizeof(dev->din)) {
  50                 debug("%s: Cannot receive %d bytes\n", __func__, din_len);
  51                 return -1;
  52         }
  53
  54         /* We represent message length as a byte */
  55         if (dout_len > 0xff) {
  56                 debug("%s: Cannot send %d bytes\n", __func__, dout_len);
  57                 return -1;
  58         }
  59
  60         /*
  61          * Clear input buffer so we don't get false hits for MSG_HEADER
  62          */
  63         memset(dev->din, '\0', in_bytes);
  64
  65         if (spi_claim_bus(dev->spi)) {
  66                 debug("%s: Cannot claim SPI bus\n", __func__);
  67                 return -1;
  68         }
  69
  70         out = dev->dout;
  71         out[0] = cmd_version;
  72         out[1] = cmd;
  73         out[2] = (uint8_t)dout_len;
  74         memcpy(out + 3, dout, dout_len);
  75         csum = cros_ec_calc_checksum(out, 3)
  76                + cros_ec_calc_checksum(dout, dout_len);
  77         out[3 + dout_len] = (uint8_t)csum;
  78
  79         /*
  80          * Send output data and receive input data starting such that the
  81          * message body will be dword aligned.
  82          */
  83         p = dev->din + sizeof(int64_t) - 2;
  84         len = dout_len + 4;
  85         cros_ec_dump_data("out", cmd, out, len);
  86         rv = spi_xfer(dev->spi, max(len, in_bytes) * 8, out, p,
  87                       SPI_XFER_BEGIN | SPI_XFER_END);
  88
  89         spi_release_bus(dev->spi);
  90
  91         if (rv) {
  92                 debug("%s: Cannot complete SPI transfer\n", __func__);
  93                 return -1;
  94         }
  95
  96         len = min(p[1], din_len);
  97         cros_ec_dump_data("in", -1, p, len + 3);
  98
  99         /* Response code is first byte of message */
 100         if (p[0] != EC_RES_SUCCESS) {
 101                 printf("%s: Returned status %d\n", __func__, p[0]);
 102                 return -(int)(p[0]);
 103         }
 104
 105         /* Check checksum */
 106         csum = cros_ec_calc_checksum(p, len + 2);
 107         if (csum != p[len + 2]) {
 108                 debug("%s: Invalid checksum rx %#02x, calced %#02x\n", __func__,
 109                       p[2 + len], csum);
 110                 return -1;
 111         }
 112
 113         /* Anything else is the response data */
 114         *dinp = p + 2;
 115
 116         return len;
 117 }
 118
 119 int cros_ec_spi_decode_fdt(struct cros_ec_dev *dev, const void *blob)
 120 {
 121         /* Decode interface-specific FDT params */
 122         dev->max_frequency = fdtdec_get_int(blob, dev->node,
 123                                             "spi-max-frequency", 500000);
 124         dev->cs = fdtdec_get_int(blob, dev->node, "reg", 0);
 125
 126         return 0;
 127 }
 128
 129 /**
 130  * Initialize SPI protocol.
 131  *
 132  * @param dev           CROS_EC device
 133  * @param blob          Device tree blob
 134  * @return 0 if ok, -1 on error
 135  */
 136 int cros_ec_spi_init(struct cros_ec_dev *dev, const void *blob)
 137 {
 138         dev->spi = spi_setup_slave_fdt(blob, dev->parent_node,
 139                                        dev->cs, dev->max_frequency, 0);
 140         if (!dev->spi) {
 141                 debug("%s: Could not setup SPI slave\n", __func__);
 142                 return -1;
 143         }
 144
 145         return 0;
 146 }