arch/arm/mach-mx2/cpu_imx27.c

   1 /*
   2  * Copyright 2007 Freescale Semiconductor, Inc. All Rights Reserved.
   3  * Copyright 2008 Juergen Beisert, kernel@pengutronix.de
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License
   7  * as published by the Free Software Foundation; either version 2
   8  * of the License, or (at your option) any later version.
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU 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,
  17  * MA 02110-1301, USA.
  18  */
  19
  20 /*
  21  * i.MX27 specific CPU detection code
  22  */
  23
  24 #include <linux/io.h>
  25 #include <linux/module.h>
  26
  27 #include <mach/hardware.h>
  28
  29 static int cpu_silicon_rev = -1;
  30 static int cpu_partnumber;
  31
  32 #define SYS_CHIP_ID             0x00    /* The offset of CHIP ID register */
  33
  34 static void query_silicon_parameter(void)
  35 {
  36         u32 val;
  37         /*
  38          * now we have access to the IO registers. As we need
  39          * the silicon revision very early we read it here to
  40          * avoid any further hooks
  41         */
  42         val = __raw_readl(IO_ADDRESS(SYSCTRL_BASE_ADDR) + SYS_CHIP_ID);
  43
  44         cpu_silicon_rev = (int)(val >> 28);
  45         cpu_partnumber = (int)((val >> 12) & 0xFFFF);
  46 }
  47
  48 /*
  49  * Returns:
  50  *      the silicon revision of the cpu
  51  *      -EINVAL - not a mx27
  52  */
  53 int mx27_revision(void)
  54 {
  55         if (cpu_silicon_rev == -1)
  56                 query_silicon_parameter();
  57
  58         if (cpu_partnumber != 0x8821)
  59                 return -EINVAL;
  60
  61         return cpu_silicon_rev;
  62 }
  63 EXPORT_SYMBOL(mx27_revision);