s390/mem_detect: replace tprot loop with binary search

In a situation when other memory detection methods are not available
(no SCLP and no z/VM diag260), continuous online memory is assumed.
Replacing tprot loop with faster binary search, as only online memory
end has to be found.

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

4 files changed, 20 insertions, 36 deletions

diff --git a/arch/s390/boot/mem_detect.c b/arch/s390/boot/mem_detect.c
index 3becf6bbe4c7..65ae3c926042 100644
--- a/arch/s390/boot/mem_detect.c
+++ b/arch/s390/boot/mem_detect.c
@@ -3,12 +3,10 @@
 #include <asm/sclp.h>
 #include <asm/sections.h>
 #include <asm/mem_detect.h>
+#include <asm/sparsemem.h>
 #include "compressed/decompressor.h"
 #include "boot.h"
 
-#define CHUNK_READ_WRITE 0
-#define CHUNK_READ_ONLY  1
-
 unsigned long __bootdata(max_physmem_end);
 struct mem_detect_info __bootdata(mem_detect);
 
@@ -141,38 +139,25 @@ static int tprot(unsigned long addr)
         return rc;
 }
 
-static void scan_memory(unsigned long rzm)
+static void search_mem_end(void)
 {
-        unsigned long addr, size;
-        int type;
-
-        if (!rzm)
-                rzm = 1UL << 20;
-
-        addr = 0;
-        do {
-                size = 0;
-                /* assume lowcore is writable */
-                type = addr ? tprot(addr) : CHUNK_READ_WRITE;
-                do {
-                        size += rzm;
-                        if (max_physmem_end && addr + size >= max_physmem_end)
-                                break;
-                } while (type == tprot(addr + size));
-                if (type == CHUNK_READ_WRITE || type == CHUNK_READ_ONLY) {
-                        if (max_physmem_end && (addr + size > max_physmem_end))
-                                size = max_physmem_end - addr;
-                        add_mem_detect_block(addr, addr + size);
-                }
-                addr += size;
-        } while (addr < max_physmem_end);
+        unsigned long range = 1 << (MAX_PHYSMEM_BITS - 20); /* in 1MB blocks */
+        unsigned long offset = 0;
+        unsigned long pivot;
+
+        while (range > 1) {
+                range >>= 1;
+                pivot = offset + range;
+                if (!tprot(pivot << 20))
+                        offset = pivot;
+        }
+
+        add_mem_detect_block(0, (offset + 1) << 20);
 }
 
 void detect_memory(void)
 {
-        unsigned long rzm;
-
-        sclp_early_get_meminfo(&max_physmem_end, &rzm);
+        sclp_early_get_memsize(&max_physmem_end);
 
         if (!sclp_early_read_storage_info()) {
                 mem_detect.info_source = MEM_DETECT_SCLP_STOR_INFO;
@@ -190,7 +175,7 @@ void detect_memory(void)
                 return;
         }
 
-        scan_memory(rzm);
-        mem_detect.info_source = MEM_DETECT_TPROT_LOOP;
+        search_mem_end();
+        mem_detect.info_source = MEM_DETECT_BIN_SEARCH;
         max_physmem_end = get_mem_detect_end();
 }
diff --git a/arch/s390/include/asm/mem_detect.h b/arch/s390/include/asm/mem_detect.h
index 153c3542fa8a..6114b92ab667 100644
--- a/arch/s390/include/asm/mem_detect.h
+++ b/arch/s390/include/asm/mem_detect.h
@@ -9,7 +9,7 @@ enum mem_info_source {
         MEM_DETECT_SCLP_STOR_INFO,
         MEM_DETECT_DIAG260,
         MEM_DETECT_SCLP_READ_INFO,
-        MEM_DETECT_TPROT_LOOP
+        MEM_DETECT_BIN_SEARCH
 };
 
 struct mem_detect_block {
diff --git a/arch/s390/include/asm/sclp.h b/arch/s390/include/asm/sclp.h
index e0da13c0ef79..32b683f6992f 100644
--- a/arch/s390/include/asm/sclp.h
+++ b/arch/s390/include/asm/sclp.h
@@ -114,7 +114,7 @@ void sclp_early_printk(const char *s);
 void sclp_early_printk_force(const char *s);
 void __sclp_early_printk(const char *s, unsigned int len, unsigned int force);
 
-int sclp_early_get_meminfo(unsigned long *mem, unsigned long *rzm);
+int sclp_early_get_memsize(unsigned long *mem);
 int _sclp_get_core_info(struct sclp_core_info *info);
 int sclp_core_configure(u8 core);
 int sclp_core_deconfigure(u8 core);
diff --git a/drivers/s390/char/sclp_early_core.c b/drivers/s390/char/sclp_early_core.c
index 0df08dcb9fe8..acfe09313852 100644
--- a/drivers/s390/char/sclp_early_core.c
+++ b/drivers/s390/char/sclp_early_core.c
@@ -272,7 +272,7 @@ int __init sclp_early_get_info(struct read_info_sccb *info)
         return 0;
 }
 
-int __init sclp_early_get_meminfo(unsigned long *mem, unsigned long *rzm)
+int __init sclp_early_get_memsize(unsigned long *mem)
 {
         unsigned long rnmax;
         unsigned long rnsize;
@@ -285,7 +285,6 @@ int __init sclp_early_get_meminfo(unsigned long *mem, unsigned long *rzm)
         rnsize = sccb->rnsize ? sccb->rnsize : sccb->rnsize2;
         rnsize <<= 20;
         *mem = rnsize * rnmax;
-        *rzm = rnsize;
         return 0;
 }