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