/* * (C) Copyright 2002 * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com. * * Influenced by code from: * Wolfgang Denk, DENX Software Engineering, wd@denx.de. * * See file CREDITS for list of people who contributed to this * project. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation; either version 2 of * the License, or (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, * MA 02111-1307 USA */ #include <common.h> #include <spi.h> #if defined(CONFIG_SOFT_SPI) /*----------------------------------------------------------------------- * Definitions */ #ifdef DEBUG_SPI #define PRINTD(fmt,args...) printf (fmt ,##args) #else #define PRINTD(fmt,args...) #endif /*=====================================================================*/ /* Public Functions */ /*=====================================================================*/ /*----------------------------------------------------------------------- * Initialization */ void spi_init (void) { #ifdef SPI_INIT volatile immap_t *immr = (immap_t *)CFG_IMMR; SPI_INIT; #endif } /*----------------------------------------------------------------------- * SPI transfer * * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks * "bitlen" bits in the SPI MISO port. That's just the way SPI works. * * The source of the outgoing bits is the "dout" parameter and the * destination of the input bits is the "din" parameter. Note that "dout" * and "din" can point to the same memory location, in which case the * input data overwrites the output data (since both are buffered by * temporary variables, this is OK). * * If the chipsel() function is not NULL, it is called with a parameter * of '1' (chip select active) at the start of the transfer and again with * a parameter of '0' at the end of the transfer. * * If the chipsel() function _is_ NULL, it the responsibility of the * caller to make the appropriate chip select active before calling * spi_xfer() and making it inactive after spi_xfer() returns. */ int spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din) { #ifdef CFG_IMMR volatile immap_t *immr = (immap_t *)CFG_IMMR; #endif uchar tmpdin = 0; uchar tmpdout = 0; int j; PRINTD("spi_xfer: chipsel %08X dout %08X din %08X bitlen %d\n", (int)chipsel, *(uint *)dout, *(uint *)din, bitlen); if(chipsel != NULL) { (*chipsel)(1); /* select the target chip */ } for(j = 0; j < bitlen; j++) { /* * Check if it is time to work on a new byte. */ if((j % 8) == 0) { tmpdout = *dout++; if(j != 0) { *din++ = tmpdin; } tmpdin = 0; } SPI_SCL(0); SPI_SDA(tmpdout & 0x80); SPI_DELAY; SPI_SCL(1); SPI_DELAY; tmpdin <<= 1; tmpdin |= SPI_READ; tmpdout <<= 1; } /* * If the number of bits isn't a multiple of 8, shift the last * bits over to left-justify them. Then store the last byte * read in. */ if((bitlen % 8) != 0) tmpdin <<= 8 - (bitlen % 8); *din++ = tmpdin; SPI_SCL(0); /* SPI wants the clock left low for idle */ if(chipsel != NULL) { (*chipsel)(0); /* deselect the target chip */ } return(0); } #endif /* CONFIG_SOFT_SPI */