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Diffstat (limited to 'common/soft_spi.c')
| -rw-r--r-- | common/soft_spi.c | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/common/soft_spi.c b/common/soft_spi.c new file mode 100644 index 0000000..a5b62f2 --- /dev/null +++ b/common/soft_spi.c @@ -0,0 +1,138 @@ +/* + * (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) + +#define DEBUG_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) +{ + volatile immap_t *immr = (immap_t *)CFG_IMMR; + 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 */ + |