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 #ifdef CONFIG_SMP
  24 /*
  25  * Get the number of CPU cores from the SCU configuration
  26  */
  27 unsigned int __init scu_get_core_count(void __iomem *scu_base)
  28 {
  29         unsigned int ncores = __raw_readl(scu_base + SCU_CONFIG);
  30         return (ncores & 0x03) + 1;
  31 }
  32
  33 /*
  34  * Enable the SCU
  35  */
  36 void __init scu_enable(void __iomem *scu_base)
  37 {
  38         u32 scu_ctrl;
  39
  40         scu_ctrl = __raw_readl(scu_base + SCU_CTRL);
  41         /* already enabled? */
  42         if (scu_ctrl & 1)
  43                 return;
  44
  45         scu_ctrl |= 1;
  46         __raw_writel(scu_ctrl, scu_base + SCU_CTRL);
  47
  48         /*
  49          * Ensure that the data accessed by CPU0 before the SCU was
  50          * initialised is visible to the other CPUs.
  51          */
  52         flush_cache_all();
  53 }
  54 #endif
  55
  56 /*
  57  * Set the executing CPUs power mode as defined.  This will be in
  58  * preparation for it executing a WFI instruction.
  59  *
  60  * This function must be called with preemption disabled, and as it
  61  * has the side effect of disabling coherency, caches must have been
  62  * flushed.  Interrupts must also have been disabled.
  63  */
  64 int scu_power_mode(void __iomem *scu_base, unsigned int mode)
  65 {
  66         unsigned int val;
  67         int cpu = smp_processor_id();
  68
  69         if (mode > 3 || mode == 1 || cpu > 3)
  70                 return -EINVAL;
  71
  72         val = __raw_readb(scu_base + SCU_CPU_STATUS + cpu) & ~0x03;
  73         val |= mode;
  74         __raw_writeb(val, scu_base + SCU_CPU_STATUS + cpu);
  75
  76         return 0;
  77 }