arch/arm/mach-prima2/rstc.c

   1 /*
   2  * reset controller for CSR SiRFprimaII
   3  *
   4  * Copyright (c) 2011 Cambridge Silicon Radio Limited, a CSR plc group company.
   5  *
   6  * Licensed under GPLv2 or later.
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/mutex.h>
  11 #include <linux/io.h>
  12 #include <linux/delay.h>
  13 #include <linux/device.h>
  14 #include <linux/of.h>
  15 #include <linux/of_address.h>
  16
  17 void __iomem *sirfsoc_rstc_base;
  18 static DEFINE_MUTEX(rstc_lock);
  19
  20 static struct of_device_id rstc_ids[]  = {
  21         { .compatible = "sirf,prima2-rstc" },
  22 };
  23
  24 static int __init sirfsoc_of_rstc_init(void)
  25 {
  26         struct device_node *np;
  27
  28         np = of_find_matching_node(NULL, rstc_ids);
  29         if (!np)
  30                 panic("unable to find compatible rstc node in dtb\n");
  31
  32         sirfsoc_rstc_base = of_iomap(np, 0);
  33         if (!sirfsoc_rstc_base)
  34                 panic("unable to map rstc cpu registers\n");
  35
  36         of_node_put(np);
  37
  38         return 0;
  39 }
  40 early_initcall(sirfsoc_of_rstc_init);
  41
  42 int sirfsoc_reset_device(struct device *dev)
  43 {
  44         const unsigned int *prop = of_get_property(dev->of_node, "reset-bit", NULL);
  45         unsigned int reset_bit;
  46
  47         if (!prop)
  48                 return -ENODEV;
  49
  50         reset_bit = be32_to_cpup(prop);
  51
  52         mutex_lock(&rstc_lock);
  53
  54         /*
  55          * Writing 1 to this bit resets corresponding block. Writing 0 to this
  56          * bit de-asserts reset signal of the corresponding block.
  57          * datasheet doesn't require explicit delay between the set and clear
  58          * of reset bit. it could be shorter if tests pass.
  59          */
  60         writel(readl(sirfsoc_rstc_base + (reset_bit / 32) * 4) | reset_bit,
  61                 sirfsoc_rstc_base + (reset_bit / 32) * 4);
  62         msleep(10);
  63         writel(readl(sirfsoc_rstc_base + (reset_bit / 32) * 4) & ~reset_bit,
  64                 sirfsoc_rstc_base + (reset_bit / 32) * 4);
  65
  66         mutex_unlock(&rstc_lock);
  67
  68         return 0;
  69 }