powerpc: Dynamic DMA zone limits

Platform code can call limit_zone_pfn() to set appropriate limits
for ZONE_DMA and ZONE_DMA32, and dma_direct_alloc_coherent() will
select a suitable zone based on a device's mask and the pfn limits that
platform code has configured.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Cc: Shaohui Xie <Shaohui.Xie@freescale.com>

4 files changed, 83 insertions, 5 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index bd6dd6ed3a9f..d003409b5f98 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -285,6 +285,10 @@ config PPC_EMULATE_SSTEP
         bool
         default y if KPROBES || UPROBES || XMON || HAVE_HW_BREAKPOINT
 
+config ZONE_DMA32
+        bool
+        default y if PPC64
+
 source "init/Kconfig"
 
 source "kernel/Kconfig.freezer"
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index d98c1ecc3266..6d74167bb6bf 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -4,6 +4,7 @@
 
 #ifndef __ASSEMBLY__
 #include <linux/mmdebug.h>
+#include <linux/mmzone.h>
 #include <asm/processor.h>              /* For TASK_SIZE */
 #include <asm/mmu.h>
 #include <asm/page.h>
@@ -281,6 +282,8 @@ extern unsigned long empty_zero_page[];
 
 extern pgd_t swapper_pg_dir[];
 
+void limit_zone_pfn(enum zone_type zone, unsigned long max_pfn);
+int dma_pfn_limit_to_zone(u64 pfn_limit);
 extern void paging_init(void);
 
 /*
diff --git a/arch/powerpc/kernel/dma.c b/arch/powerpc/kernel/dma.c
index ee78f6e49d64..dfd99ef8c63d 100644
--- a/arch/powerpc/kernel/dma.c
+++ b/arch/powerpc/kernel/dma.c
@@ -40,6 +40,26 @@ void *dma_direct_alloc_coherent(struct device *dev, size_t size,
 #else
         struct page *page;
         int node = dev_to_node(dev);
+        u64 pfn = (dev->coherent_dma_mask >> PAGE_SHIFT) + 1;
+        int zone;
+
+        zone = dma_pfn_limit_to_zone(pfn);
+        if (zone < 0) {
+                dev_err(dev, "%s: No suitable zone for pfn %#llx\n",
+                        __func__, pfn);
+                return NULL;
+        }
+
+        switch (zone) {
+        case ZONE_DMA:
+                flag |= GFP_DMA;
+                break;
+#ifdef CONFIG_ZONE_DMA32
+        case ZONE_DMA32:
+                flag |= GFP_DMA32;
+                break;
+#endif
+        };
 
         /* ignore region specifiers */
         flag  &= ~(__GFP_HIGHMEM);
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 2c8e90f5789e..687e7f7f7751 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -260,6 +260,54 @@ static int __init mark_nonram_nosave(void)
         return 0;
 }
 
+static bool zone_limits_final;
+
+static unsigned long max_zone_pfns[MAX_NR_ZONES] = {
+        [0 ... MAX_NR_ZONES - 1] = ~0UL
+};
+
+/*
+ * Restrict the specified zone and all more restrictive zones
+ * to be below the specified pfn.  May not be called after
+ * paging_init().
+ */
+void __init limit_zone_pfn(enum zone_type zone, unsigned long pfn_limit)
+{
+        int i;
+
+        if (WARN_ON(zone_limits_final))
+                return;
+
+        for (i = zone; i >= 0; i--) {
+                if (max_zone_pfns[i] > pfn_limit)
+                        max_zone_pfns[i] = pfn_limit;
+        }
+}
+
+/*
+ * Find the least restrictive zone that is entirely below the
+ * specified pfn limit.  Returns < 0 if no suitable zone is found.
+ *
+ * pfn_limit must be u64 because it can exceed 32 bits even on 32-bit
+ * systems -- the DMA limit can be higher than any possible real pfn.
+ */
+int dma_pfn_limit_to_zone(u64 pfn_limit)
+{
+        enum zone_type top_zone = ZONE_NORMAL;
+        int i;
+
+#ifdef CONFIG_HIGHMEM
+        top_zone = ZONE_HIGHMEM;
+#endif
+
+        for (i = top_zone; i >= 0; i--) {
+                if (max_zone_pfns[i] <= pfn_limit)
+                        return i;
+        }
+
+        return -EPERM;
+}
+
 /*
  * paging_init() sets up the page tables - in fact we've already done this.
  */
@@ -267,7 +315,7 @@ void __init paging_init(void)
 {
         unsigned long long total_ram = memblock_phys_mem_size();
         phys_addr_t top_of_ram = memblock_end_of_DRAM();
-        unsigned long max_zone_pfns[MAX_NR_ZONES];
+        enum zone_type top_zone;
 
 #ifdef CONFIG_PPC32
         unsigned long v = __fix_to_virt(__end_of_fixed_addresses - 1);
@@ -289,13 +337,16 @@ void __init paging_init(void)
                (unsigned long long)top_of_ram, total_ram);
         printk(KERN_DEBUG "Memory hole size: %ldMB\n",
                (long int)((top_of_ram - total_ram) >> 20));
-        memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
+
 #ifdef CONFIG_HIGHMEM
-        max_zone_pfns[ZONE_DMA] = lowmem_end_addr >> PAGE_SHIFT;
-        max_zone_pfns[ZONE_HIGHMEM] = top_of_ram >> PAGE_SHIFT;
+        top_zone = ZONE_HIGHMEM;
+        limit_zone_pfn(ZONE_NORMAL, lowmem_end_addr >> PAGE_SHIFT);
 #else
-        max_zone_pfns[ZONE_DMA] = top_of_ram >> PAGE_SHIFT;
+        top_zone = ZONE_NORMAL;
 #endif
+
+        limit_zone_pfn(top_zone, top_of_ram >> PAGE_SHIFT);
+        zone_limits_final = true;
         free_area_init_nodes(max_zone_pfns);
 
         mark_nonram_nosave();