mm: create generic early_ioremap() support

This patch creates a generic implementation of early_ioremap() support
based on the existing x86 implementation.  early_ioremp() is useful for
early boot code which needs to temporarily map I/O or memory regions
before normal mapping functions such as ioremap() are available.

Some architectures have optional MMU.  In the no-MMU case, the remap
functions simply return the passed in physical address and the unmap
functions do nothing.

Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Cc: Borislav Petkov <borislav.petkov@amd.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 249 insertions, 0 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index 37fbe1ef5239..ebe5880c29d6 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -578,3 +578,6 @@ config PGTABLE_MAPPING
 
           You can check speed with zsmalloc benchmark:
           https://github.com/spartacus06/zsmapbench
+
+config GENERIC_EARLY_IOREMAP
+        bool
diff --git a/mm/Makefile b/mm/Makefile
index 23a6f7e23019..9e5aaf92197d 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -61,3 +61,4 @@ obj-$(CONFIG_CLEANCACHE) += cleancache.o
 obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
 obj-$(CONFIG_ZBUD)      += zbud.o
 obj-$(CONFIG_ZSMALLOC)  += zsmalloc.o
+obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
diff --git a/mm/early_ioremap.c b/mm/early_ioremap.c
new file mode 100644
index 000000000000..e10ccd299d66
--- /dev/null
+++ b/mm/early_ioremap.c
@@ -0,0 +1,245 @@
+/*
+ * Provide common bits of early_ioremap() support for architectures needing
+ * temporary mappings during boot before ioremap() is available.
+ *
+ * This is mostly a direct copy of the x86 early_ioremap implementation.
+ *
+ * (C) Copyright 1995 1996, 2014 Linus Torvalds
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <asm/fixmap.h>
+
+#ifdef CONFIG_MMU
+static int early_ioremap_debug __initdata;
+
+static int __init early_ioremap_debug_setup(char *str)
+{
+        early_ioremap_debug = 1;
+
+        return 0;
+}
+early_param("early_ioremap_debug", early_ioremap_debug_setup);
+
+static int after_paging_init __initdata;
+
+void __init __weak early_ioremap_shutdown(void)
+{
+}
+
+void __init early_ioremap_reset(void)
+{
+        early_ioremap_shutdown();
+        after_paging_init = 1;
+}
+
+/*
+ * Generally, ioremap() is available after paging_init() has been called.
+ * Architectures wanting to allow early_ioremap after paging_init() can
+ * define __late_set_fixmap and __late_clear_fixmap to do the right thing.
+ */
+#ifndef __late_set_fixmap
+static inline void __init __late_set_fixmap(enum fixed_addresses idx,
+                                            phys_addr_t phys, pgprot_t prot)
+{
+        BUG();
+}
+#endif
+
+#ifndef __late_clear_fixmap
+static inline void __init __late_clear_fixmap(enum fixed_addresses idx)
+{
+        BUG();
+}
+#endif
+
+static void __iomem *prev_map[FIX_BTMAPS_SLOTS] __initdata;
+static unsigned long prev_size[FIX_BTMAPS_SLOTS] __initdata;
+static unsigned long slot_virt[FIX_BTMAPS_SLOTS] __initdata;
+
+void __init early_ioremap_setup(void)
+{
+        int i;
+
+        for (i = 0; i < FIX_BTMAPS_SLOTS; i++)
+                if (WARN_ON(prev_map[i]))
+                        break;
+
+        for (i = 0; i < FIX_BTMAPS_SLOTS; i++)
+                slot_virt[i] = __fix_to_virt(FIX_BTMAP_BEGIN - NR_FIX_BTMAPS*i);
+}
+
+static int __init check_early_ioremap_leak(void)
+{
+        int count = 0;
+        int i;
+
+        for (i = 0; i < FIX_BTMAPS_SLOTS; i++)
+                if (prev_map[i])
+                        count++;
+
+        if (WARN(count, KERN_WARNING
+                 "Debug warning: early ioremap leak of %d areas detected.\n"
+                 "please boot with early_ioremap_debug and report the dmesg.\n",
+                 count))
+                return 1;
+        return 0;
+}
+late_initcall(check_early_ioremap_leak);
+
+static void __init __iomem *
+__early_ioremap(resource_size_t phys_addr, unsigned long size, pgprot_t prot)
+{
+        unsigned long offset;
+        resource_size_t last_addr;
+        unsigned int nrpages;
+        enum fixed_addresses idx;
+        int i, slot;
+
+        WARN_ON(system_state != SYSTEM_BOOTING);
+
+        slot = -1;
+        for (i = 0; i < FIX_BTMAPS_SLOTS; i++) {
+                if (!prev_map[i]) {
+                        slot = i;
+                        break;
+                }
+        }
+
+        if (WARN(slot < 0, "%s(%08llx, %08lx) not found slot\n",
+                 __func__, (u64)phys_addr, size))
+                return NULL;
+
+        /* Don't allow wraparound or zero size */
+        last_addr = phys_addr + size - 1;
+        if (WARN_ON(!size || last_addr < phys_addr))
+                return NULL;
+
+        prev_size[slot] = size;
+        /*
+         * Mappings have to be page-aligned
+         */
+        offset = phys_addr & ~PAGE_MASK;
+        phys_addr &= PAGE_MASK;
+        size = PAGE_ALIGN(last_addr + 1) - phys_addr;
+
+        /*
+         * Mappings have to fit in the FIX_BTMAP area.
+         */
+        nrpages = size >> PAGE_SHIFT;
+        if (WARN_ON(nrpages > NR_FIX_BTMAPS))
+                return NULL;
+
+        /*
+         * Ok, go for it..
+         */
+        idx = FIX_BTMAP_BEGIN - NR_FIX_BTMAPS*slot;
+        while (nrpages > 0) {
+                if (after_paging_init)
+                        __late_set_fixmap(idx, phys_addr, prot);
+                else
+                        __early_set_fixmap(idx, phys_addr, prot);
+                phys_addr += PAGE_SIZE;
+                --idx;
+                --nrpages;
+        }
+        WARN(early_ioremap_debug, "%s(%08llx, %08lx) [%d] => %08lx + %08lx\n",
+             __func__, (u64)phys_addr, size, slot, offset, slot_virt[slot]);
+
+        prev_map[slot] = (void __iomem *)(offset + slot_virt[slot]);
+        return prev_map[slot];
+}
+
+void __init early_iounmap(void __iomem *addr, unsigned long size)
+{
+        unsigned long virt_addr;
+        unsigned long offset;
+        unsigned int nrpages;
+        enum fixed_addresses idx;
+        int i, slot;
+
+        slot = -1;
+        for (i = 0; i < FIX_BTMAPS_SLOTS; i++) {
+                if (prev_map[i] == addr) {
+                        slot = i;
+                        break;
+                }
+        }
+
+        if (WARN(slot < 0, "early_iounmap(%p, %08lx) not found slot\n",
+                 addr, size))
+                return;
+
+        if (WARN(prev_size[slot] != size,
+                 "early_iounmap(%p, %08lx) [%d] size not consistent %08lx\n",
+                 addr, size, slot, prev_size[slot]))
+                return;
+
+        WARN(early_ioremap_debug, "early_iounmap(%p, %08lx) [%d]\n",
+             addr, size, slot);
+
+        virt_addr = (unsigned long)addr;
+        if (WARN_ON(virt_addr < fix_to_virt(FIX_BTMAP_BEGIN)))
+                return;
+
+        offset = virt_addr & ~PAGE_MASK;
+        nrpages = PAGE_ALIGN(offset + size) >> PAGE_SHIFT;
+
+        idx = FIX_BTMAP_BEGIN - NR_FIX_BTMAPS*slot;
+        while (nrpages > 0) {
+                if (after_paging_init)
+                        __late_clear_fixmap(idx);
+                else
+                        __early_set_fixmap(idx, 0, FIXMAP_PAGE_CLEAR);
+                --idx;
+                --nrpages;
+        }
+        prev_map[slot] = NULL;
+}
+
+/* Remap an IO device */
+void __init __iomem *
+early_ioremap(resource_size_t phys_addr, unsigned long size)
+{
+        return __early_ioremap(phys_addr, size, FIXMAP_PAGE_IO);
+}
+
+/* Remap memory */
+void __init *
+early_memremap(resource_size_t phys_addr, unsigned long size)
+{
+        return (__force void *)__early_ioremap(phys_addr, size,
+                                               FIXMAP_PAGE_NORMAL);
+}
+#else /* CONFIG_MMU */
+
+void __init __iomem *
+early_ioremap(resource_size_t phys_addr, unsigned long size)
+{
+        return (__force void __iomem *)phys_addr;
+}
+
+/* Remap memory */
+void __init *
+early_memremap(resource_size_t phys_addr, unsigned long size)
+{
+        return (void *)phys_addr;
+}
+
+void __init early_iounmap(void __iomem *addr, unsigned long size)
+{
+}
+
+#endif /* CONFIG_MMU */
+
+
+void __init early_memunmap(void *addr, unsigned long size)
+{
+        early_iounmap((__force void __iomem *)addr, size);
+}