arch/arm/kernel/smp_scu.c

   1 /*
   2  *  linux/arch/arm/kernel/smp_scu.c
   3  *
   4  *  Copyright (C) 2002 ARM Ltd.
   5  *  All Rights Reserved
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11 #include <linux/init.h>
  12 #include <linux/io.h>
  13
  14 #include <asm/smp_scu.h>
  15 #include <asm/cacheflush.h>
  16
  17 #define SCU_CTRL                0x00
  18 #define SCU_CONFIG              0x04
  19 #define SCU_CPU_STATUS          0x08
  20 #define SCU_INVALIDATE          0x0c
  21 #define SCU_FPGA_REVISION       0x10
  22
  23 /*
  24  * Get the number of CPU cores from the SCU configuration
  25  */
  26 unsigned int __init scu_get_core_count(void __iomem *scu_base)
  27 {
  28         unsigned int ncores = __raw_readl(scu_base + SCU_CONFIG);
  29         return (ncores & 0x03) + 1;
  30 }
  31
  32 /*
  33  * Enable the SCU
  34  */
  35 void __init scu_enable(void __iomem *scu_base)
  36 {
  37         u32 scu_ctrl;
  38
  39         scu_ctrl = __raw_readl(scu_base + SCU_CTRL);
  40         /* already enabled? */
  41         if (scu_ctrl & 1)
  42                 return;
  43
  44         scu_ctrl |= 1;
  45         __raw_writel(scu_ctrl, scu_base + SCU_CTRL);
  46
  47         /*
  48          * Ensure that the data accessed by CPU0 before the SCU was
  49          * initialised is visible to the other CPUs.
  50          */
  51         flush_cache_all();
  52 }
  53
  54 /*
  55  * Set the executing CPUs power mode as defined.  This will be in
  56  * preparation for it executing a WFI instruction.
  57  *
  58  * This function must be called with preemption disabled, and as it
  59  * has the side effect of disabling coherency, caches must have been
  60  * flushed.  Interrupts must also have been disabled.
  61  */
  62 int scu_power_mode(void __iomem *scu_base, unsigned int mode)
  63 {
  64         unsigned int val;
  65         int cpu = smp_processor_id();
  66
  67         if (mode > 3 || mode == 1 || cpu > 3)
  68                 return -EINVAL;
  69
  70         val = __raw_readb(scu_base + SCU_CPU_STATUS + cpu) & ~0x03;
  71         val |= mode;
  72         __raw_writeb(val, scu_base + SCU_CPU_STATUS + cpu);
  73
  74         return 0;
  75 }