src/drivers/nvs/threewire.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., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 #include <stddef.h>
  20 #include <assert.h>
  21 #include <timer.h>
  22 #include <gpxe/threewire.h>
  23
  24 /** @file
  25  *
  26  * Three-wire serial devices
  27  *
  28  */
  29
  30 /**
  31  * Read data from three-wire device
  32  *
  33  * @v nvs               NVS device
  34  * @v address           Address from which to read
  35  * @v data              Data buffer
  36  * @v len               Length of data buffer
  37  * @ret rc              Return status code
  38  */
  39 int threewire_read ( struct nvs_device *nvs, unsigned int address,
  40                      void *data, size_t len ) {
  41         struct spi_device *device = nvs_to_spi ( nvs );
  42         struct spi_bus *bus = device->bus;
  43
  44         assert ( bus->mode == SPI_MODE_THREEWIRE );
  45
  46         DBG ( "3wire %p reading %d bytes at %04x\n", device, len, address );
  47
  48         return bus->rw ( bus, device, THREEWIRE_READ, address,
  49                          NULL, data, len );
  50 }
  51
  52 /**
  53  * Write data to three-wire device
  54  *
  55  * @v nvs               NVS device
  56  * @v address           Address from which to read
  57  * @v data              Data buffer
  58  * @v len               Length of data buffer
  59  * @ret rc              Return status code
  60  */
  61 int threewire_write ( struct nvs_device *nvs, unsigned int address,
  62                       const void *data, size_t len ) {
  63         struct spi_device *device = nvs_to_spi ( nvs );
  64         struct spi_bus *bus = device->bus;
  65         int rc;
  66
  67         assert ( bus->mode == SPI_MODE_THREEWIRE );
  68
  69         DBG ( "3wire %p writing %d bytes at %04x\n", device, len, address );
  70
  71         /* Enable device for writing */
  72         if ( ( rc = bus->rw ( bus, device, THREEWIRE_EWEN,
  73                               THREEWIRE_EWEN_ADDRESS, NULL, NULL, 0 ) ) != 0 )
  74                 return rc;
  75
  76         /* Write data */
  77         if ( ( rc = bus->rw ( bus, device, THREEWIRE_WRITE, address,
  78                               data, NULL, len ) ) != 0 )
  79                 return rc;
  80
  81         /* Our model of an SPI bus doesn't provide a mechanism for
  82          * "assert CS, wait for MISO to become high, so just wait for
  83          * long enough to ensure that the write has completed.
  84          */
  85         mdelay ( THREEWIRE_WRITE_MDELAY );
  86
  87         return 0;
  88 }