ARC: support HIGHMEM even without PAE40

Initial HIGHMEM support on ARC was introduced for PAE40 where the low
memory (0x8000_0000 based) and high memory (0x1_0000_0000) were
physically contiguous. So CONFIG_FLATMEM sufficed (despite a peipheral
hole in the middle, which wasted a bit of struct page memory, but things
worked).

However w/o PAE, highmem was not possible and we could only reach
~1.75GB of DDR. Now there is a use case to access ~4GB of DDR w/o PAE40
The idea is to have low memory at canonical 0x8000_0000 and highmem
at 0 so enire 4GB address space is available for physical addressing
This needs additional platform/interconnect mapping to convert
the non contiguous physical addresses into linear bus adresses.

From Linux point of view, non contiguous divide means FLATMEM no
longer works and DISCONTIGMEM is needed to track the pfns in the 2
regions.

This scheme would also work for PAE40, only better in that we don't
waste struct page memory for the peripheral hole.

The DT description will be something like

    memory {
        ...
        reg = <0x80000000 0x200000000   /* 512MB: lowmem */
               0x00000000 0x10000000>;  /* 256MB: highmem */
   }

Signed-off-by: Noam Camus <noamc@ezchip.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index ec4791ea691196bf7137b99ead768b3cc030a056..a8767430df7d6012463c8a34366d251496d15364 100644 (file)
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -58,6 +58,9 @@ config GENERIC_CSUM
 config RWSEM_GENERIC_SPINLOCK
        def_bool y
 
+config ARCH_DISCONTIGMEM_ENABLE
+       def_bool y
+
 config ARCH_FLATMEM_ENABLE
        def_bool y
 
@@ -347,6 +350,15 @@ config ARC_HUGEPAGE_16M
 
 endchoice
 
+config NODES_SHIFT
+       int "Maximum NUMA Nodes (as a power of 2)"
+       default "1" if !DISCONTIGMEM
+       default "2" if DISCONTIGMEM
+       depends on NEED_MULTIPLE_NODES
+       ---help---
+         Accessing memory beyond 1GB (with or w/o PAE) requires 2 memory
+         zones.
+
 if ISA_ARCOMPACT
 
 config ARC_COMPACT_IRQ_LEVELS
@@ -455,6 +467,7 @@ config LINUX_LINK_BASE
 
 config HIGHMEM
        bool "High Memory Support"
+       select DISCONTIGMEM
        help
          With ARC 2G:2G address split, only upper 2G is directly addressable by
          kernel. Enable this to potentially allow access to rest of 2G and PAE

diff --git a/arch/arc/include/asm/mmzone.h b/arch/arc/include/asm/mmzone.h
new file mode 100644 (file)
index 0000000..8e97136
--- /dev/null
+++ b/arch/arc/include/asm/mmzone.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2016 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _ASM_ARC_MMZONE_H
+#define _ASM_ARC_MMZONE_H
+
+#ifdef CONFIG_DISCONTIGMEM
+
+extern struct pglist_data node_data[];
+#define NODE_DATA(nid) (&node_data[nid])
+
+static inline int pfn_to_nid(unsigned long pfn)
+{
+       int is_end_low = 1;
+
+       if (IS_ENABLED(CONFIG_ARC_HAS_PAE40))
+               is_end_low = pfn <= virt_to_pfn(0xFFFFFFFFUL);
+
+       /*
+        * node 0: lowmem:             0x8000_0000   to 0xFFFF_FFFF
+        * node 1: HIGHMEM w/o  PAE40: 0x0           to 0x7FFF_FFFF
+        *         HIGHMEM with PAE40: 0x1_0000_0000 to ...
+        */
+       if (pfn >= ARCH_PFN_OFFSET && is_end_low)
+               return 0;
+
+       return 1;
+}
+
+static inline int pfn_valid(unsigned long pfn)
+{
+       int nid = pfn_to_nid(pfn);
+
+       return (pfn <= node_end_pfn(nid));
+}
+#endif /* CONFIG_DISCONTIGMEM  */
+
+#endif

diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h
index 533e5a0c6ba52cdc458a33f9d678d9f9a62c1bce..0d53854884d047557a981fece15936715a4cd950 100644 (file)
--- a/arch/arc/include/asm/page.h
+++ b/arch/arc/include/asm/page.h
@@ -83,7 +83,9 @@ typedef pte_t * pgtable_t;
 
 #define ARCH_PFN_OFFSET                virt_to_pfn(CONFIG_LINUX_LINK_BASE)
 
+#ifdef CONFIG_FLATMEM
 #define pfn_valid(pfn)         (((pfn) - ARCH_PFN_OFFSET) < max_mapnr)
+#endif
 
 /*
  * __pa, __va, virt_to_page (ALERT: deprecated, don't use them)
@@ -95,9 +97,7 @@ typedef pte_t * pgtable_t;
 #define __pa(vaddr)  ((unsigned long)(vaddr))
 #define __va(paddr)  ((void *)((unsigned long)(paddr)))
 
-#define virt_to_page(kaddr)    \
-       (mem_map + virt_to_pfn((kaddr) - CONFIG_LINUX_LINK_BASE))
-
+#define virt_to_page(kaddr)    pfn_to_page(virt_to_pfn(kaddr))
 #define virt_addr_valid(kaddr)  pfn_valid(virt_to_pfn(kaddr))
 
 /* Default Permissions for stack/heaps pages (Non Executable) */

diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
index 5487d0b974005621a8cfaf119bdbf1f687d9ff7b..8be930394750a7cf7039a9dcc85cf6ee1994f4e6 100644 (file)
--- a/arch/arc/mm/init.c
+++ b/arch/arc/mm/init.c
@@ -30,11 +30,16 @@ static const unsigned long low_mem_start = CONFIG_LINUX_LINK_BASE;
 static unsigned long low_mem_sz;
 
 #ifdef CONFIG_HIGHMEM
-static unsigned long min_high_pfn;
+static unsigned long min_high_pfn, max_high_pfn;
 static u64 high_mem_start;
 static u64 high_mem_sz;
 #endif
 
+#ifdef CONFIG_DISCONTIGMEM
+struct pglist_data node_data[MAX_NUMNODES] __read_mostly;
+EXPORT_SYMBOL(node_data);
+#endif
+
 /* User can over-ride above with "mem=nnn[KkMm]" in cmdline */
 static int __init setup_mem_sz(char *str)
 {
@@ -109,13 +114,11 @@ void __init setup_arch_memory(void)
        /* Last usable page of low mem */
        max_low_pfn = max_pfn = PFN_DOWN(low_mem_start + low_mem_sz);
 
-#ifdef CONFIG_HIGHMEM
-       min_high_pfn = PFN_DOWN(high_mem_start);
-       max_pfn = PFN_DOWN(high_mem_start + high_mem_sz);
+#ifdef CONFIG_FLATMEM
+       /* pfn_valid() uses this */
+       max_mapnr = max_low_pfn - min_low_pfn;
 #endif
 
-       max_mapnr = max_pfn - min_low_pfn;
-
        /*------------- bootmem allocator setup -----------------------*/
 
        /*
@@ -129,7 +132,7 @@ void __init setup_arch_memory(void)
         * the crash
         */
 
-       memblock_add(low_mem_start, low_mem_sz);
+       memblock_add_node(low_mem_start, low_mem_sz, 0);
        memblock_reserve(low_mem_start, __pa(_end) - low_mem_start);
 
 #ifdef CONFIG_BLK_DEV_INITRD
@@ -149,13 +152,6 @@ void __init setup_arch_memory(void)
        zones_size[ZONE_NORMAL] = max_low_pfn - min_low_pfn;
        zones_holes[ZONE_NORMAL] = 0;
 
-#ifdef CONFIG_HIGHMEM
-       zones_size[ZONE_HIGHMEM] = max_pfn - max_low_pfn;
-
-       /* This handles the peripheral address space hole */
-       zones_holes[ZONE_HIGHMEM] = min_high_pfn - max_low_pfn;
-#endif
-
        /*
         * We can't use the helper free_area_init(zones[]) because it uses
         * PAGE_OFFSET to compute the @min_low_pfn which would be wrong
@@ -168,6 +164,34 @@ void __init setup_arch_memory(void)
                            zones_holes);       /* holes */
 
 #ifdef CONFIG_HIGHMEM
+       /*
+        * Populate a new node with highmem
+        *
+        * On ARC (w/o PAE) HIGHMEM addresses are actually smaller (0 based)
+        * than addresses in normal ala low memory (0x8000_0000 based).
+        * Even with PAE, the huge peripheral space hole would waste a lot of
+        * mem with single mem_map[]. This warrants a mem_map per region design.
+        * Thus HIGHMEM on ARC is imlemented with DISCONTIGMEM.
+        *
+        * DISCONTIGMEM in turns requires multiple nodes. node 0 above is
+        * populated with normal memory zone while node 1 only has highmem
+        */
+       node_set_online(1);
+
+       min_high_pfn = PFN_DOWN(high_mem_start);
+       max_high_pfn = PFN_DOWN(high_mem_start + high_mem_sz);
+
+       zones_size[ZONE_NORMAL] = 0;
+       zones_holes[ZONE_NORMAL] = 0;
+
+       zones_size[ZONE_HIGHMEM] = max_high_pfn - min_high_pfn;
+       zones_holes[ZONE_HIGHMEM] = 0;
+
+       free_area_init_node(1,                  /* node-id */
+                           zones_size,         /* num pages per zone */
+                           min_high_pfn,       /* first pfn of node */
+                           zones_holes);       /* holes */
+
        high_memory = (void *)(min_high_pfn << PAGE_SHIFT);
        kmap_init();
 #endif
@@ -185,7 +209,7 @@ void __init mem_init(void)
        unsigned long tmp;
 
        reset_all_zones_managed_pages();
-       for (tmp = min_high_pfn; tmp < max_pfn; tmp++)
+       for (tmp = min_high_pfn; tmp < max_high_pfn; tmp++)
                free_highmem_page(pfn_to_page(tmp));
 #endif