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wdenke3093092002-10-01 01:07:28 +00001/*
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#define DEBUG_SPI
33
34
35/*-----------------------------------------------------------------------
36 * Definitions
37 */
38
39#ifdef DEBUG_SPI
40#define PRINTD(fmt,args...) printf (fmt ,##args)
41#else
42#define PRINTD(fmt,args...)
43#endif
44
45
46
47/*=====================================================================*/
48/* Public Functions */
49/*=====================================================================*/
50
51/*-----------------------------------------------------------------------
52 * Initialization
53 */
54void spi_init (void)
55{
56#ifdef SPI_INIT
57 volatile immap_t *immr = (immap_t *)CFG_IMMR;
58
59 SPI_INIT;
60#endif
61}
62
63
64/*-----------------------------------------------------------------------
65 * SPI transfer
66 *
67 * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
68 * "bitlen" bits in the SPI MISO port. That's just the way SPI works.
69 *
70 * The source of the outgoing bits is the "dout" parameter and the
71 * destination of the input bits is the "din" parameter. Note that "dout"
72 * and "din" can point to the same memory location, in which case the
73 * input data overwrites the output data (since both are buffered by
74 * temporary variables, this is OK).
75 *
76 * If the chipsel() function is not NULL, it is called with a parameter
77 * of '1' (chip select active) at the start of the transfer and again with
78 * a parameter of '0' at the end of the transfer.
79 *
80 * If the chipsel() function _is_ NULL, it the responsibility of the
81 * caller to make the appropriate chip select active before calling
82 * spi_xfer() and making it inactive after spi_xfer() returns.
83 */
84int spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din)
85{
86 volatile immap_t *immr = (immap_t *)CFG_IMMR;
87 uchar tmpdin = 0;
88 uchar tmpdout = 0;
89 int j;
90
91 PRINTD("spi_xfer: chipsel %08X dout %08X din %08X bitlen %d\n",
92 (int)chipsel, *(uint *)dout, *(uint *)din, bitlen);
93
94 if(chipsel != NULL) {
95 (*chipsel)(1); /* select the target chip */
96 }
97
98 for(j = 0; j < bitlen; j++) {
99 /*
100 * Check if it is time to work on a new byte.
101 */
102 if((j % 8) == 0) {
103 tmpdout = *dout++;
104 if(j != 0) {
105 *din++ = tmpdin;
106 }
107 tmpdin = 0;
108 }
109 SPI_SCL(0);
110 SPI_SDA(tmpdout & 0x80);
111 SPI_DELAY;
112 SPI_SCL(1);
113 SPI_DELAY;
114 tmpdin <<= 1;
115 tmpdin |= SPI_READ;
116 tmpdout <<= 1;
117 }
118 /*
119 * If the number of bits isn't a multiple of 8, shift the last
120 * bits over to left-justify them. Then store the last byte
121 * read in.
122 */
123 if((bitlen % 8) != 0)
124 tmpdin <<= 8 - (bitlen % 8);
125 *din++ = tmpdin;
126
127 SPI_SCL(0); /* SPI wants the clock left low for idle */
128
129 if(chipsel != NULL) {
130 (*chipsel)(0); /* deselect the target chip */
131
132 }
133
134 return(0);
135}
136
137#endif /* CONFIG_SOFT_SPI */
138