On 05/17/2012 07:54 PM, Marek Szyprowski wrote:
> 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.
>
I like this patch very much!
There are just small nitpicks below.
> Atomic allocations are served from special pool preallocated on boot,
> becasue vmalloc areas cannot be reliably created in atomic context.
typo because
>
> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> ---
> 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);
Out of curiosity.
Do we always map dma area into user's address space?
> + 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);
Why do we need vmlist_lock?
> + area = find_vm_area(cpu_addr);
find_vm_area only checks vmalloced regions so we need more check.
if (!area || !(area->flags & VM_DMA))
> + 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;
Nitpick. What does count mean?
nr_pages?
> + void *vaddr;
> + struct page *page;
> +};
> +
> +static struct dma_pool atomic_pool = {
> + .size = SZ_256K,
> +};
AFAIUC, we could set it to 2M but you are reducing it to 256K.
What's the justification for that default value?
> +
> +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;
> }
--
Kind regards,
Minchan Kim
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