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mem_detect.c

/*
 *    Copyright IBM Corp. 2008
 *    Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <asm/ipl.h>
#include <asm/sclp.h>
#include <asm/setup.h>

static inline int tprot(unsigned long addr)
{
      int rc = -EFAULT;

      asm volatile(
            "     tprot 0(%1),0\n"
            "0:   ipm   %0\n"
            "     srl   %0,28\n"
            "1:\n"
            EX_TABLE(0b,1b)
            : "+d" (rc) : "a" (addr) : "cc");
      return rc;
}

#define ADDR2G (1ULL << 31)

static void find_memory_chunks(struct mem_chunk chunk[])
{
      unsigned long long memsize, rnmax, rzm;
      unsigned long addr = 0, size;
      int i = 0, type;

      rzm = sclp_get_rzm();
      rnmax = sclp_get_rnmax();
      memsize = rzm * rnmax;
      if (!rzm)
            rzm = 1ULL << 17;
      if (sizeof(long) == 4) {
            rzm = min(ADDR2G, rzm);
            memsize = memsize ? min(ADDR2G, memsize) : ADDR2G;
      }
      do {
            size = 0;
            type = tprot(addr);
            do {
                  size += rzm;
                  if (memsize && addr + size >= memsize)
                        break;
            } while (type == tprot(addr + size));
            if (type == CHUNK_READ_WRITE || type == CHUNK_READ_ONLY) {
                  chunk[i].addr = addr;
                  chunk[i].size = size;
                  chunk[i].type = type;
                  i++;
            }
            addr += size;
      } while (addr < memsize && i < MEMORY_CHUNKS);
}

void detect_memory_layout(struct mem_chunk chunk[])
{
      unsigned long flags, cr0;

      memset(chunk, 0, MEMORY_CHUNKS * sizeof(struct mem_chunk));
      /* Disable IRQs, DAT and low address protection so tprot does the
       * right thing and we don't get scheduled away with low address
       * protection disabled.
       */
      flags = __raw_local_irq_stnsm(0xf8);
      __ctl_store(cr0, 0, 0);
      __ctl_clear_bit(0, 28);
      find_memory_chunks(chunk);
      __ctl_load(cr0, 0, 0);
      __raw_local_irq_ssm(flags);
}
EXPORT_SYMBOL(detect_memory_layout);

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