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Subject[PATCHv2 4/4] ARM: dma-mapping: remove custom consistent dma region
This patch changes dma-mapping subsystem to use generic vmalloc areas
for all consistent dma allocations. This increases the total size limit
of the consistent allocations and removes platform hacks and a lot of
duplicated code.

Atomic allocations are served from special pool preallocated on boot,
becasue vmalloc areas cannot be reliably created in atomic context.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
Documentation/kernel-parameters.txt | 4 +
arch/arm/include/asm/dma-mapping.h | 2 +-
arch/arm/mm/dma-mapping.c | 360 ++++++++++++++++-------------------
3 files changed, 171 insertions(+), 195 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index c1601e5..ba58f50 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -515,6 +515,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
a hypervisor.
Default: yes

+ coherent_pool=nn[KMG] [ARM,KNL]
+ Sets the size of memory pool for coherent, atomic dma
+ allocations.
+
code_bytes [X86] How many bytes of object code to print
in an oops report.
Range: 0 - 8192
diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
index cb3b7c9..92b0afb 100644
--- a/arch/arm/include/asm/dma-mapping.h
+++ b/arch/arm/include/asm/dma-mapping.h
@@ -210,7 +210,7 @@ int dma_mmap_writecombine(struct device *, struct vm_area_struct *,
* DMA region above it's default value of 2MB. It must be called before the
* memory allocator is initialised, i.e. before any core_initcall.
*/
-extern void __init init_consistent_dma_size(unsigned long size);
+static inline void init_consistent_dma_size(unsigned long size) { }


#ifdef CONFIG_DMABOUNCE
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index db23ae4..3be4de2 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -19,6 +19,8 @@
#include <linux/dma-mapping.h>
#include <linux/highmem.h>
#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/vmalloc.h>

#include <asm/memory.h>
#include <asm/highmem.h>
@@ -119,210 +121,178 @@ static void __dma_free_buffer(struct page *page, size_t size)
}

#ifdef CONFIG_MMU
-
-#define CONSISTENT_OFFSET(x) (((unsigned long)(x) - consistent_base) >> PAGE_SHIFT)
-#define CONSISTENT_PTE_INDEX(x) (((unsigned long)(x) - consistent_base) >> PMD_SHIFT)
-
-/*
- * These are the page tables (2MB each) covering uncached, DMA consistent allocations
- */
-static pte_t **consistent_pte;
-
-#define DEFAULT_CONSISTENT_DMA_SIZE SZ_2M
-
-unsigned long consistent_base = CONSISTENT_END - DEFAULT_CONSISTENT_DMA_SIZE;
-
-void __init init_consistent_dma_size(unsigned long size)
-{
- unsigned long base = CONSISTENT_END - ALIGN(size, SZ_2M);
-
- BUG_ON(consistent_pte); /* Check we're called before DMA region init */
- BUG_ON(base < VMALLOC_END);
-
- /* Grow region to accommodate specified size */
- if (base < consistent_base)
- consistent_base = base;
-}
-
-#include "vmregion.h"
-
-static struct arm_vmregion_head consistent_head = {
- .vm_lock = __SPIN_LOCK_UNLOCKED(&consistent_head.vm_lock),
- .vm_list = LIST_HEAD_INIT(consistent_head.vm_list),
- .vm_end = CONSISTENT_END,
-};
-
#ifdef CONFIG_HUGETLB_PAGE
#error ARM Coherent DMA allocator does not (yet) support huge TLB
#endif

-/*
- * Initialise the consistent memory allocation.
- */
-static int __init consistent_init(void)
-{
- int ret = 0;
- pgd_t *pgd;
- pud_t *pud;
- pmd_t *pmd;
- pte_t *pte;
- int i = 0;
- unsigned long base = consistent_base;
- unsigned long num_ptes = (CONSISTENT_END - base) >> PMD_SHIFT;
-
- consistent_pte = kmalloc(num_ptes * sizeof(pte_t), GFP_KERNEL);
- if (!consistent_pte) {
- pr_err("%s: no memory\n", __func__);
- return -ENOMEM;
- }
-
- pr_debug("DMA memory: 0x%08lx - 0x%08lx:\n", base, CONSISTENT_END);
- consistent_head.vm_start = base;
-
- do {
- pgd = pgd_offset(&init_mm, base);
-
- pud = pud_alloc(&init_mm, pgd, base);
- if (!pud) {
- printk(KERN_ERR "%s: no pud tables\n", __func__);
- ret = -ENOMEM;
- break;
- }
-
- pmd = pmd_alloc(&init_mm, pud, base);
- if (!pmd) {
- printk(KERN_ERR "%s: no pmd tables\n", __func__);
- ret = -ENOMEM;
- break;
- }
- WARN_ON(!pmd_none(*pmd));
-
- pte = pte_alloc_kernel(pmd, base);
- if (!pte) {
- printk(KERN_ERR "%s: no pte tables\n", __func__);
- ret = -ENOMEM;
- break;
- }
-
- consistent_pte[i++] = pte;
- base += PMD_SIZE;
- } while (base < CONSISTENT_END);
-
- return ret;
-}
-
-core_initcall(consistent_init);
-
static void *
__dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
const void *caller)
{
- struct arm_vmregion *c;
- size_t align;
- int bit;
+ struct vm_struct *area;
+ unsigned long addr;

- if (!consistent_pte) {
- printk(KERN_ERR "%s: not initialised\n", __func__);
+ area = get_vm_area_caller(size, VM_DMA | VM_USERMAP, caller);
+ if (!area)
+ return NULL;
+ addr = (unsigned long)area->addr;
+ area->phys_addr = __pfn_to_phys(page_to_pfn(page));
+
+ if (ioremap_page_range(addr, addr + size, area->phys_addr, prot)) {
+ vunmap((void *)addr);
+ return NULL;
+ }
+ return (void *)addr;
+}
+
+static void __dma_free_remap(void *cpu_addr, size_t size)
+{
+ struct vm_struct *area;
+
+ read_lock(&vmlist_lock);
+ area = find_vm_area(cpu_addr);
+ if (!area) {
+ pr_err("%s: trying to free invalid coherent area: %p\n",
+ __func__, cpu_addr);
+ dump_stack();
+ read_unlock(&vmlist_lock);
+ return;
+ }
+ unmap_kernel_range((unsigned long)cpu_addr, size);
+ read_unlock(&vmlist_lock);
+ vunmap(cpu_addr);
+}
+
+struct dma_pool {
+ size_t size;
+ spinlock_t lock;
+ unsigned long *bitmap;
+ unsigned long count;
+ void *vaddr;
+ struct page *page;
+};
+
+static struct dma_pool atomic_pool = {
+ .size = SZ_256K,
+};
+
+static int __init early_coherent_pool(char *p)
+{
+ atomic_pool.size = memparse(p, &p);
+ return 0;
+}
+early_param("coherent_pool", early_coherent_pool);
+
+/*
+ * Initialise the coherent pool for atomic allocations.
+ */
+static int __init atomic_pool_init(void)
+{
+ struct dma_pool *pool = &atomic_pool;
+ pgprot_t prot = pgprot_dmacoherent(pgprot_kernel);
+ unsigned long count = pool->size >> PAGE_SHIFT;
+ gfp_t gfp = GFP_KERNEL | GFP_DMA;
+ unsigned long *bitmap;
+ struct page *page;
+ void *ptr;
+ int bitmap_size = BITS_TO_LONGS(count) * sizeof(long);
+
+ bitmap = kzalloc(bitmap_size, GFP_KERNEL);
+ if (!bitmap)
+ goto no_bitmap;
+
+ page = __dma_alloc_buffer(NULL, pool->size, gfp);
+ if (!page)
+ goto no_page;
+
+ ptr = __dma_alloc_remap(page, pool->size, gfp, prot, NULL);
+ if (ptr) {
+ spin_lock_init(&pool->lock);
+ pool->vaddr = ptr;
+ pool->page = page;
+ pool->bitmap = bitmap;
+ pool->count = count;
+ pr_info("DMA: preallocated %u KiB pool for atomic coherent allocations\n",
+ (unsigned)pool->size / 1024);
+ return 0;
+ }
+
+ __dma_free_buffer(page, pool->size);
+no_page:
+ kfree(bitmap);
+no_bitmap:
+ pr_err("DMA: failed to allocate %u KiB pool for atomic coherent allocation\n",
+ (unsigned)pool->size / 1024);
+ return -ENOMEM;
+}
+core_initcall(atomic_pool_init);
+
+static void *__alloc_from_pool(size_t size, struct page **ret_page)
+{
+ struct dma_pool *pool = &atomic_pool;
+ unsigned int count = size >> PAGE_SHIFT;
+ unsigned int pageno;
+ unsigned long flags;
+ void *ptr = NULL;
+ size_t align;
+
+ if (!pool->vaddr) {
+ pr_err("%s: coherent pool not initialised!\n", __func__);
dump_stack();
return NULL;
}

/*
- * Align the virtual region allocation - maximum alignment is
- * a section size, minimum is a page size. This helps reduce
- * fragmentation of the DMA space, and also prevents allocations
- * smaller than a section from crossing a section boundary.
+ * Align the region allocation - allocations from pool are rather
+ * small, so align them to their order in pages, minimum is a page
+ * size. This helps reduce fragmentation of the DMA space.
*/
- bit = fls(size - 1);
- if (bit > SECTION_SHIFT)
- bit = SECTION_SHIFT;
- align = 1 << bit;
+ align = PAGE_SIZE << get_order(size);

- /*
- * Allocate a virtual address in the consistent mapping region.
- */
- c = arm_vmregion_alloc(&consistent_head, align, size,
- gfp & ~(__GFP_DMA | __GFP_HIGHMEM), caller);
- if (c) {
- pte_t *pte;
- int idx = CONSISTENT_PTE_INDEX(c->vm_start);
- u32 off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
-
- pte = consistent_pte[idx] + off;
- c->vm_pages = page;
-
- do {
- BUG_ON(!pte_none(*pte));
-
- set_pte_ext(pte, mk_pte(page, prot), 0);
- page++;
- pte++;
- off++;
- if (off >= PTRS_PER_PTE) {
- off = 0;
- pte = consistent_pte[++idx];
- }
- } while (size -= PAGE_SIZE);
-
- dsb();
-
- return (void *)c->vm_start;
+ spin_lock_irqsave(&pool->lock, flags);
+ pageno = bitmap_find_next_zero_area(pool->bitmap, pool->count,
+ 0, count, (1 << align) - 1);
+ if (pageno < pool->count) {
+ bitmap_set(pool->bitmap, pageno, count);
+ ptr = pool->vaddr + PAGE_SIZE * pageno;
+ *ret_page = pool->page + pageno;
}
- return NULL;
+ spin_unlock_irqrestore(&pool->lock, flags);
+
+ return ptr;
}

-static void __dma_free_remap(void *cpu_addr, size_t size)
+static int __free_from_pool(void *start, size_t size)
{
- struct arm_vmregion *c;
- unsigned long addr;
- pte_t *ptep;
- int idx;
- u32 off;
+ struct dma_pool *pool = &atomic_pool;
+ unsigned long pageno, count;
+ unsigned long flags;

- c = arm_vmregion_find_remove(&consistent_head, (unsigned long)cpu_addr);
- if (!c) {
- printk(KERN_ERR "%s: trying to free invalid coherent area: %p\n",
- __func__, cpu_addr);
+ if (start < pool->vaddr || start > pool->vaddr + pool->size)
+ return 0;
+
+ if (start + size > pool->vaddr + pool->size) {
+ pr_err("%s: freeing wrong coherent size from pool\n", __func__);
dump_stack();
- return;
+ return 0;
}

- if ((c->vm_end - c->vm_start) != size) {
- printk(KERN_ERR "%s: freeing wrong coherent size (%ld != %d)\n",
- __func__, c->vm_end - c->vm_start, size);
- dump_stack();
- size = c->vm_end - c->vm_start;
- }
+ pageno = (start - pool->vaddr) >> PAGE_SHIFT;
+ count = size >> PAGE_SHIFT;

- idx = CONSISTENT_PTE_INDEX(c->vm_start);
- off = CONSISTENT_OFFSET(c->vm_start) & (PTRS_PER_PTE-1);
- ptep = consistent_pte[idx] + off;
- addr = c->vm_start;
- do {
- pte_t pte = ptep_get_and_clear(&init_mm, addr, ptep);
+ spin_lock_irqsave(&pool->lock, flags);
+ bitmap_clear(pool->bitmap, pageno, count);
+ spin_unlock_irqrestore(&pool->lock, flags);

- ptep++;
- addr += PAGE_SIZE;
- off++;
- if (off >= PTRS_PER_PTE) {
- off = 0;
- ptep = consistent_pte[++idx];
- }
-
- if (pte_none(pte) || !pte_present(pte))
- printk(KERN_CRIT "%s: bad page in kernel page table\n",
- __func__);
- } while (size -= PAGE_SIZE);
-
- flush_tlb_kernel_range(c->vm_start, c->vm_end);
-
- arm_vmregion_free(&consistent_head, c);
+ return 1;
}

#else /* !CONFIG_MMU */

#define __dma_alloc_remap(page, size, gfp, prot, c) page_address(page)
#define __dma_free_remap(addr, size) do { } while (0)
+#define __alloc_from_pool(size, ret_page) NULL
+#define __free_from_pool(addr, size) 0

#endif /* CONFIG_MMU */

@@ -345,6 +315,16 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
*handle = ~0;
size = PAGE_ALIGN(size);

+ /*
+ * Atomic allocations need special handling
+ */
+ if (gfp & GFP_ATOMIC && !arch_is_coherent()) {
+ addr = __alloc_from_pool(size, &page);
+ if (addr)
+ *handle = pfn_to_dma(dev, page_to_pfn(page));
+ return addr;
+ }
+
page = __dma_alloc_buffer(dev, size, gfp);
if (!page)
return NULL;
@@ -398,24 +378,16 @@ static int dma_mmap(struct device *dev, struct vm_area_struct *vma,
{
int ret = -ENXIO;
#ifdef CONFIG_MMU
- unsigned long user_size, kern_size;
- struct arm_vmregion *c;
+ unsigned long user_count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+ unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+ unsigned long pfn = dma_to_pfn(dev, dma_addr);
+ unsigned long off = vma->vm_pgoff;

- user_size = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
-
- c = arm_vmregion_find(&consistent_head, (unsigned long)cpu_addr);
- if (c) {
- unsigned long off = vma->vm_pgoff;
-
- kern_size = (c->vm_end - c->vm_start) >> PAGE_SHIFT;
-
- if (off < kern_size &&
- user_size <= (kern_size - off)) {
- ret = remap_pfn_range(vma, vma->vm_start,
- page_to_pfn(c->vm_pages) + off,
- user_size << PAGE_SHIFT,
- vma->vm_page_prot);
- }
+ if (off < count && user_count <= (count - off)) {
+ ret = remap_pfn_range(vma, vma->vm_start,
+ pfn + off,
+ user_count << PAGE_SHIFT,
+ vma->vm_page_prot);
}
#endif /* CONFIG_MMU */

@@ -444,13 +416,16 @@ EXPORT_SYMBOL(dma_mmap_writecombine);
*/
void dma_free_coherent(struct device *dev, size_t size, void *cpu_addr, dma_addr_t handle)
{
- WARN_ON(irqs_disabled());
-
if (dma_release_from_coherent(dev, get_order(size), cpu_addr))
return;

size = PAGE_ALIGN(size);

+ if (__free_from_pool(cpu_addr, size))
+ return;
+
+ WARN_ON(irqs_disabled());
+
if (!arch_is_coherent())
__dma_free_remap(cpu_addr, size);

@@ -726,9 +701,6 @@ EXPORT_SYMBOL(dma_set_mask);

static int __init dma_debug_do_init(void)
{
-#ifdef CONFIG_MMU
- arm_vmregion_create_proc("dma-mappings", &consistent_head);
-#endif
dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
return 0;
}
--
1.7.10.1


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