iPXE
spi.c
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00001 /*
00002  * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
00003  *
00004  * This program is free software; you can redistribute it and/or
00005  * modify it under the terms of the GNU General Public License as
00006  * published by the Free Software Foundation; either version 2 of the
00007  * License, or any later version.
00008  *
00009  * This program is distributed in the hope that it will be useful, but
00010  * WITHOUT ANY WARRANTY; without even the implied warranty of
00011  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012  * General Public License for more details.
00013  *
00014  * You should have received a copy of the GNU General Public License
00015  * along with this program; if not, write to the Free Software
00016  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
00017  * 02110-1301, USA.
00018  *
00019  * You can also choose to distribute this program under the terms of
00020  * the Unmodified Binary Distribution Licence (as given in the file
00021  * COPYING.UBDL), provided that you have satisfied its requirements.
00022  */
00023 
00024 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
00025 
00026 #include <stddef.h>
00027 #include <errno.h>
00028 #include <unistd.h>
00029 #include <ipxe/spi.h>
00030 
00031 /** @file
00032  *
00033  * SPI devices
00034  *
00035  */
00036 
00037 /**
00038  * Munge SPI device address into command
00039  *
00040  * @v command           SPI command
00041  * @v address           Address
00042  * @v munge_address     Device requires address munging
00043  * @ret command         Actual SPI command to use
00044  *
00045  * Some devices with 9-bit addresses (e.g. AT25040A EEPROM) use bit 3
00046  * of the command byte as address bit A8, rather than having a
00047  * two-byte address.  This function takes care of generating the
00048  * appropriate command.
00049  */
00050 static inline unsigned int spi_command ( unsigned int command,
00051                                          unsigned int address,
00052                                          int munge_address ) {
00053         return ( command | ( ( ( address >> 8 ) & munge_address ) << 3 ) );
00054 }
00055 
00056 /**
00057  * Wait for SPI device to complete operation
00058  *
00059  * @v device            SPI device
00060  * @ret rc              Return status code
00061  */
00062 static int spi_wait ( struct spi_device *device ) {
00063         struct spi_bus *bus = device->bus;
00064         uint8_t status;
00065         int i;
00066         int rc;
00067 
00068         for ( i = 0 ; i < 50 ; i++ ) {
00069                 udelay ( 20 );
00070                 if ( ( rc = bus->rw ( bus, device, SPI_RDSR, -1, NULL,
00071                                       &status, sizeof ( status ) ) ) != 0 )
00072                         return rc;
00073                 if ( ! ( status & SPI_STATUS_NRDY ) )
00074                         return 0;
00075         }
00076         DBG ( "SPI %p timed out\n", device );
00077         return -ETIMEDOUT;
00078 }
00079 
00080 /**
00081  * Read data from SPI device
00082  *
00083  * @v nvs               NVS device
00084  * @v address           Address from which to read
00085  * @v data              Data buffer
00086  * @v len               Length of data buffer
00087  * @ret rc              Return status code
00088  */
00089 int spi_read ( struct nvs_device *nvs, unsigned int address,
00090                void *data, size_t len ) {
00091         struct spi_device *device = nvs_to_spi ( nvs );
00092         struct spi_bus *bus = device->bus;
00093         unsigned int command = spi_command ( SPI_READ, address,
00094                                              device->munge_address );
00095         int rc;
00096 
00097         DBG ( "SPI %p reading %zd bytes from %#04x\n", device, len, address );
00098         if ( ( rc = bus->rw ( bus, device, command, address,
00099                               NULL, data, len ) ) != 0 ) {
00100                 DBG ( "SPI %p failed to read data from device\n", device );
00101                 return rc;
00102         }
00103 
00104         return 0;
00105 }
00106 
00107 /**
00108  * Write data to SPI device
00109  *
00110  * @v nvs               NVS device
00111  * @v address           Address from which to read
00112  * @v data              Data buffer
00113  * @v len               Length of data buffer
00114  * @ret rc              Return status code
00115  */
00116 int spi_write ( struct nvs_device *nvs, unsigned int address,
00117                 const void *data, size_t len ) {
00118         struct spi_device *device = nvs_to_spi ( nvs );
00119         struct spi_bus *bus = device->bus;
00120         unsigned int command = spi_command ( SPI_WRITE, address,
00121                                              device->munge_address );
00122         int rc;
00123 
00124         DBG ( "SPI %p writing %zd bytes to %#04x\n", device, len, address );
00125 
00126         if ( ( rc = bus->rw ( bus, device, SPI_WREN, -1,
00127                               NULL, NULL, 0 ) ) != 0 ) {
00128                 DBG ( "SPI %p failed to write-enable device\n", device );
00129                 return rc;
00130         }
00131 
00132         if ( ( rc = bus->rw ( bus, device, command, address,
00133                               data, NULL, len ) ) != 0 ) {
00134                 DBG ( "SPI %p failed to write data to device\n", device );
00135                 return rc;
00136         }
00137         
00138         if ( ( rc = spi_wait ( device ) ) != 0 ) {
00139                 DBG ( "SPI %p failed to complete write operation\n", device );
00140                 return rc;
00141         }
00142 
00143         return 0;
00144 }
00145