src/drivers/bitbash/spi_bit.c

   1 /*
   2  * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA.
  18  *
  19  * You can also choose to distribute this program under the terms of
  20  * the Unmodified Binary Distribution Licence (as given in the file
  21  * COPYING.UBDL), provided that you have satisfied its requirements.
  22  */
  23
  24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  25
  26 #include <stddef.h>
  27 #include <stdint.h>
  28 #include <string.h>
  29 #include <byteswap.h>
  30 #include <errno.h>
  31 #include <assert.h>
  32 #include <unistd.h>
  33 #include <ipxe/bitbash.h>
  34 #include <ipxe/spi_bit.h>
  35
  36 /** @file
  37  *
  38  * SPI bit-bashing interface
  39  *
  40  */
  41
  42 /** Delay between SCLK changes and around SS changes */
  43 static void spi_bit_delay ( void ) {
  44         udelay ( SPI_BIT_UDELAY );
  45 }
  46
  47 /** Chip select line will be asserted */
  48 #define SELECT_SLAVE 0
  49
  50 /** Chip select line will be deasserted */
  51 #define DESELECT_SLAVE SPI_MODE_SSPOL
  52
  53 /**
  54  * Select/deselect slave
  55  *
  56  * @v spibit            SPI bit-bashing interface
  57  * @v slave             Slave number
  58  * @v state             Slave select state
  59  *
  60  * @c state must be @c SELECT_SLAVE or @c DESELECT_SLAVE.
  61  */
  62 static void spi_bit_set_slave_select ( struct spi_bit_basher *spibit,
  63                                        unsigned int slave,
  64                                        unsigned int state ) {
  65         struct bit_basher *basher = &spibit->basher;
  66
  67         state ^= ( spibit->bus.mode & SPI_MODE_SSPOL );
  68         DBGC2 ( spibit, "SPIBIT %p setting slave %d select %s\n",
  69                 spibit, slave, ( state ? "high" : "low" ) );
  70
  71         spi_bit_delay();
  72         write_bit ( basher, SPI_BIT_SS ( slave ), state );
  73         spi_bit_delay();
  74 }
  75
  76 /**
  77  * Transfer bits over SPI bit-bashing bus
  78  *
  79  * @v bus               SPI bus
  80  * @v data_out          TX data buffer (or NULL)
  81  * @v data_in           RX data buffer (or NULL)
  82  * @v len               Length of transfer (in @b bits)
  83  * @v endianness        Endianness of this data transfer
  84  *
  85  * This issues @c len clock cycles on the SPI bus, shifting out data
  86  * from the @c data_out buffer to the MOSI line and shifting in data
  87  * from the MISO line to the @c data_in buffer.  If @c data_out is
  88  * NULL, then the data sent will be all zeroes.  If @c data_in is
  89  * NULL, then the incoming data will be discarded.
  90  */
  91 static void spi_bit_transfer ( struct spi_bit_basher *spibit,
  92                                const void *data_out, void *data_in,
  93                                unsigned int len, int endianness ) {
  94         struct spi_bus *bus = &spibit->bus;
  95         struct bit_basher *basher = &spibit->basher;
  96         unsigned int sclk = ( ( bus->mode & SPI_MODE_CPOL ) ? 1 : 0 );
  97         unsigned int cpha = ( ( bus->mode & SPI_MODE_CPHA ) ? 1 : 0 );
  98         unsigned int bit_offset;
  99         unsigned int byte_offset;
 100         unsigned int byte_mask;
 101         unsigned int bit;
 102         unsigned int step;
 103
 104         DBGC2 ( spibit, "SPIBIT %p transferring %d bits in mode %#x\n",
 105                 spibit, len, bus->mode );
 106
 107         for ( step = 0 ; step < ( len * 2 ) ; step++ ) {
 108                 /* Calculate byte offset and byte mask */
 109                 bit_offset = ( ( endianness == SPI_BIT_BIG_ENDIAN ) ?
 110                                ( len - ( step / 2 ) - 1 ) : ( step / 2 ) );
 111                 byte_offset = ( bit_offset / 8 );
 112                 byte_mask = ( 1 << ( bit_offset % 8 ) );
 113
 114                 /* Shift data in or out */
 115                 if ( sclk == cpha ) {
 116                         const uint8_t *byte;
 117
 118                         /* Shift data out */
 119                         if ( data_out ) {
 120                                 byte = ( data_out + byte_offset );
 121                                 bit = ( *byte & byte_mask );
 122                                 DBGCP ( spibit, "SPIBIT %p wrote bit %d\n",
 123                                         spibit, ( bit ? 1 : 0 ) );
 124                         } else {
 125                                 bit = 0;
 126                         }
 127                         write_bit ( basher, SPI_BIT_MOSI, bit );
 128                 } else {
 129                         uint8_t *byte;
 130
 131                         /* Shift data in */
 132                         bit = read_bit ( basher, SPI_BIT_MISO );
 133                         if ( data_in ) {
 134                                 DBGCP ( spibit, "SPIBIT %p read bit %d\n",
 135                                         spibit, ( bit ? 1 : 0 ) );
 136                                 byte = ( data_in + byte_offset );
 137                                 *byte &= ~byte_mask;
 138                                 *byte |= ( bit & byte_mask );
 139                         }
 140                 }
 141
 142                 /* Toggle clock line */
 143                 spi_bit_delay();
 144                 sclk ^= 1;
 145                 write_bit ( basher, SPI_BIT_SCLK, sclk );
 146         }
 147 }
 148
 149 /**
 150  * Read/write data via SPI bit-bashing bus
 151  *
 152  * @v bus               SPI bus
 153  * @v device            SPI device
 154  * @v command           Command
 155  * @v address           Address to read/write (<0 for no address)
 156  * @v data_out          TX data buffer (or NULL)
 157  * @v data_in           RX data buffer (or NULL)
 158  * @v len               Length of transfer
 159  * @ret rc              Return status code
 160  */
 161 static int spi_bit_rw ( struct spi_bus *bus, struct spi_device *device,
 162                         unsigned int command, int address,
 163                         const void *data_out, void *data_in, size_t len ) {
 164         struct spi_bit_basher *spibit
 165                 = container_of ( bus, struct spi_bit_basher, bus );
 166         uint32_t tmp_command;
 167         uint32_t tmp_address;
 168         uint32_t tmp_address_detect;
 169
 170         /* Open bit-bashing interface */
 171         open_bit ( &spibit->basher );
 172
 173         /* Deassert chip select to reset specified slave */
 174         spi_bit_set_slave_select ( spibit, device->slave, DESELECT_SLAVE );
 175
 176         /* Set clock line to idle state */
 177         write_bit ( &spibit->basher, SPI_BIT_SCLK,
 178                     ( bus->mode & SPI_MODE_CPOL ) );
 179
 180         /* Assert chip select on specified slave */
 181         spi_bit_set_slave_select ( spibit, device->slave, SELECT_SLAVE );
 182
 183         /* Transmit command */
 184         assert ( device->command_len <= ( 8 * sizeof ( tmp_command ) ) );
 185         tmp_command = cpu_to_le32 ( command );
 186         spi_bit_transfer ( spibit, &tmp_command, NULL, device->command_len,
 187                            SPI_BIT_BIG_ENDIAN );
 188
 189         /* Transmit address, if present */
 190         if ( address >= 0 ) {
 191                 assert ( device->address_len <= ( 8 * sizeof ( tmp_address )));
 192                 tmp_address = cpu_to_le32 ( address );
 193                 if ( device->address_len == SPI_AUTODETECT_ADDRESS_LEN ) {
 194                         /* Autodetect address length.  This relies on
 195                          * the device responding with a dummy zero
 196                          * data bit before the first real data bit.
 197                          */
 198                         DBGC ( spibit, "SPIBIT %p autodetecting device "
 199                                "address length\n", spibit );
 200                         assert ( address == 0 );
 201                         device->address_len = 0;
 202                         do {
 203                                 spi_bit_transfer ( spibit, &tmp_address,
 204                                                    &tmp_address_detect, 1,
 205                                                    SPI_BIT_BIG_ENDIAN );
 206                                 device->address_len++;
 207                         } while ( le32_to_cpu ( tmp_address_detect ) & 1 );
 208                         DBGC ( spibit, "SPIBIT %p autodetected device address "
 209                                "length %d\n", spibit, device->address_len );
 210                 } else {
 211                         spi_bit_transfer ( spibit, &tmp_address, NULL,
 212                                            device->address_len,
 213                                            SPI_BIT_BIG_ENDIAN );
 214                 }
 215         }
 216
 217         /* Transmit/receive data */
 218         spi_bit_transfer ( spibit, data_out, data_in, ( len * 8 ),
 219                            spibit->endianness );
 220
 221         /* Deassert chip select on specified slave */
 222         spi_bit_set_slave_select ( spibit, device->slave, DESELECT_SLAVE );
 223
 224         /* Close bit-bashing interface */
 225         close_bit ( &spibit->basher );
 226
 227         return 0;
 228 }
 229
 230 /**
 231  * Initialise SPI bit-bashing interface
 232  *
 233  * @v spibit            SPI bit-bashing interface
 234  */
 235 void init_spi_bit_basher ( struct spi_bit_basher *spibit ) {
 236         assert ( &spibit->basher.op->read != NULL );
 237         assert ( &spibit->basher.op->write != NULL );
 238         spibit->bus.rw = spi_bit_rw;
 239 }