common/soft_spi.c

   1 /*
   2  * (C) Copyright 2002
   3  * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
   4  *
   5  * Influenced by code from:
   6  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   7  *
   8  * See file CREDITS for list of people who contributed to this
   9  * project.
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License as
  13  * published by the Free Software Foundation; either version 2 of
  14  * the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  24  * MA 02111-1307 USA
  25  */
  26
  27 #include <common.h>
  28 #include <spi.h>
  29
  30 #if defined(CONFIG_SOFT_SPI)
  31
  32 /*-----------------------------------------------------------------------
  33  * Definitions
  34  */
  35
  36 #ifdef DEBUG_SPI
  37 #define PRINTD(fmt,args...)     printf (fmt ,##args)
  38 #else
  39 #define PRINTD(fmt,args...)
  40 #endif
  41
  42
  43 /*=====================================================================*/
  44 /*                         Public Functions                            */
  45 /*=====================================================================*/
  46
  47 /*-----------------------------------------------------------------------
  48  * Initialization
  49  */
  50 void spi_init (void)
  51 {
  52 #ifdef  SPI_INIT
  53         volatile immap_t *immr = (immap_t *)CFG_IMMR;
  54
  55         SPI_INIT;
  56 #endif
  57 }
  58
  59
  60 /*-----------------------------------------------------------------------
  61  * SPI transfer
  62  *
  63  * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
  64  * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
  65  *
  66  * The source of the outgoing bits is the "dout" parameter and the
  67  * destination of the input bits is the "din" parameter.  Note that "dout"
  68  * and "din" can point to the same memory location, in which case the
  69  * input data overwrites the output data (since both are buffered by
  70  * temporary variables, this is OK).
  71  *
  72  * If the chipsel() function is not NULL, it is called with a parameter
  73  * of '1' (chip select active) at the start of the transfer and again with
  74  * a parameter of '0' at the end of the transfer.
  75  *
  76  * If the chipsel() function _is_ NULL, it the responsibility of the
  77  * caller to make the appropriate chip select active before calling
  78  * spi_xfer() and making it inactive after spi_xfer() returns.
  79  */
  80 int  spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din)
  81 {
  82 #ifdef CFG_IMMR
  83         volatile immap_t *immr = (immap_t *)CFG_IMMR;
  84 #endif
  85         uchar tmpdin  = 0;
  86         uchar tmpdout = 0;
  87         int   j;
  88
  89         PRINTD("spi_xfer: chipsel %08X dout %08X din %08X bitlen %d\n",
  90                 (int)chipsel, *(uint *)dout, *(uint *)din, bitlen);
  91
  92         if(chipsel != NULL) {
  93                 (*chipsel)(1);  /* select the target chip */
  94         }
  95
  96         for(j = 0; j < bitlen; j++) {
  97                 /*
  98                  * Check if it is time to work on a new byte.
  99                  */
 100                 if((j % 8) == 0) {
 101                         tmpdout = *dout++;
 102                         if(j != 0) {
 103                                 *din++ = tmpdin;
 104                         }
 105                         tmpdin  = 0;
 106                 }
 107                 SPI_SCL(0);
 108                 SPI_SDA(tmpdout & 0x80);
 109                 SPI_DELAY;
 110                 SPI_SCL(1);
 111                 SPI_DELAY;
 112                 tmpdin  <<= 1;
 113                 tmpdin   |= SPI_READ;
 114                 tmpdout <<= 1;
 115         }
 116         /*
 117          * If the number of bits isn't a multiple of 8, shift the last
 118          * bits over to left-justify them.  Then store the last byte
 119          * read in.
 120          */
 121         if((bitlen % 8) != 0)
 122                 tmpdin <<= 8 - (bitlen % 8);
 123         *din++ = tmpdin;
 124
 125         SPI_SCL(0);             /* SPI wants the clock left low for idle */
 126
 127         if(chipsel != NULL) {
 128                 (*chipsel)(0);  /* deselect the target chip */
 129
 130         }
 131
 132         return(0);
 133 }
 134
 135 #endif  /* CONFIG_SOFT_SPI */