[PATCH 2/2] arm/dma-mapping: Respect NO_KERNEL_MAPPING when we don't have an IOMMU
Carlo Caione
carlo at caione.org
Tue Feb 3 11:13:36 PST 2015
On Tue, Feb 3, 2015 at 6:54 PM, Laura Abbott <lauraa at codeaurora.org> wrote:
> On 2/3/2015 12:47 AM, Carlo Caione wrote:
>>
>> From: "Jasper St. Pierre" <jstpierre at mecheye.net>
>>
>> Even without an iommu, NO_KERNEL_MAPPING is still convenient to save on
>> kernel address space in places where we don't need a kernel mapping.
>> Implement support for it in the two places where we're creating an
>> expensive mapping.
>>
>> __alloc_from_pool uses an internal pool from which we already have
>> virtual addresses, so it's not relevant, and __alloc_simple_buffer
>> uses alloc_pages, which will always return a lowmem page, which is
>> already mapped into kernel space, so we can't prevent a mapping for it
>> in that case.
>>
>> Signed-off-by: Jasper St. Pierre <jstpierre at mecheye.net>
>> Signed-off-by: Carlo Caione <carlo at caione.org>
>> Reviewed-by: Rob Clark <robdclark at gmail.com>
>> Reviewed-by: Daniel Drake <dsd at endlessm.com>
>> ---
>> arch/arm/mm/dma-mapping.c | 67
>> +++++++++++++++++++++++++++++------------------
>> 1 file changed, 41 insertions(+), 26 deletions(-)
>>
>> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>> index a673c7f..6843293 100644
>> --- a/arch/arm/mm/dma-mapping.c
>> +++ b/arch/arm/mm/dma-mapping.c
>> @@ -289,11 +289,11 @@ static void __dma_free_buffer(struct page *page,
>> size_t size)
>>
>> static void *__alloc_from_contiguous(struct device *dev, size_t size,
>> pgprot_t prot, struct page
>> **ret_page,
>> - const void *caller);
>> + const void *caller, bool want_vaddr);
>>
>> static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t
>> gfp,
>> pgprot_t prot, struct page **ret_page,
>> - const void *caller);
>> + const void *caller, bool want_vaddr);
>>
>> static void *
>> __dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t
>> prot,
>> @@ -357,10 +357,10 @@ static int __init atomic_pool_init(void)
>>
>> if (dev_get_cma_area(NULL))
>> ptr = __alloc_from_contiguous(NULL, atomic_pool_size,
>> prot,
>> - &page, atomic_pool_init);
>> + &page, atomic_pool_init,
>> true);
>> else
>> ptr = __alloc_remap_buffer(NULL, atomic_pool_size, gfp,
>> prot,
>> - &page, atomic_pool_init);
>> + &page, atomic_pool_init, true);
>> if (ptr) {
>> int ret;
>>
>> @@ -467,13 +467,15 @@ static void __dma_remap(struct page *page, size_t
>> size, pgprot_t prot)
>>
>> static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t
>> gfp,
>> pgprot_t prot, struct page **ret_page,
>> - const void *caller)
>> + const void *caller, bool want_vaddr)
>> {
>> struct page *page;
>> - void *ptr;
>> + void *ptr = NULL;
>> page = __dma_alloc_buffer(dev, size, gfp);
>> if (!page)
>> return NULL;
>> + if (!want_vaddr)
>> + goto out;
>>
>> ptr = __dma_alloc_remap(page, size, gfp, prot, caller);
>> if (!ptr) {
>> @@ -481,6 +483,7 @@ static void *__alloc_remap_buffer(struct device *dev,
>> size_t size, gfp_t gfp,
>> return NULL;
>> }
>>
>> + out:
>> *ret_page = page;
>> return ptr;
>> }
>> @@ -523,12 +526,12 @@ static int __free_from_pool(void *start, size_t
>> size)
>>
>> static void *__alloc_from_contiguous(struct device *dev, size_t size,
>> pgprot_t prot, struct page
>> **ret_page,
>> - const void *caller)
>> + const void *caller, bool want_vaddr)
>> {
>> unsigned long order = get_order(size);
>> size_t count = size >> PAGE_SHIFT;
>> struct page *page;
>> - void *ptr;
>> + void *ptr = NULL;
>>
>> page = dma_alloc_from_contiguous(dev, count, order);
>> if (!page)
>> @@ -536,6 +539,9 @@ static void *__alloc_from_contiguous(struct device
>> *dev, size_t size,
>>
>> __dma_clear_buffer(page, size);
>>
>> + if (!want_vaddr)
>> + goto out;
>> +
>> if (PageHighMem(page)) {
>> ptr = __dma_alloc_remap(page, size, GFP_KERNEL, prot,
>> caller);
>> if (!ptr) {
>> @@ -546,17 +552,21 @@ static void *__alloc_from_contiguous(struct device
>> *dev, size_t size,
>> __dma_remap(page, size, prot);
>> ptr = page_address(page);
>> }
>> +
>> + out:
>> *ret_page = page;
>> return ptr;
>> }
>>
>> static void __free_from_contiguous(struct device *dev, struct page
>> *page,
>> - void *cpu_addr, size_t size)
>> + void *cpu_addr, size_t size, bool
>> want_vaddr)
>> {
>> - if (PageHighMem(page))
>> - __dma_free_remap(cpu_addr, size);
>> - else
>> - __dma_remap(page, size, PAGE_KERNEL);
>> + if (want_vaddr) {
>> + if (PageHighMem(page))
>> + __dma_free_remap(cpu_addr, size);
>> + else
>> + __dma_remap(page, size, PAGE_KERNEL);
>> + }
>> dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT);
>> }
>>
>> @@ -574,12 +584,12 @@ static inline pgprot_t __get_dma_pgprot(struct
>> dma_attrs *attrs, pgprot_t prot)
>>
>> #define nommu() 1
>>
>> -#define __get_dma_pgprot(attrs, prot) __pgprot(0)
>> -#define __alloc_remap_buffer(dev, size, gfp, prot, ret, c) NULL
>> +#define __get_dma_pgprot(attrs, prot)
>> __pgprot(0)
>> +#define __alloc_remap_buffer(dev, size, gfp, prot, ret, c, wv) NULL
>> #define __alloc_from_pool(size, ret_page) NULL
>> -#define __alloc_from_contiguous(dev, size, prot, ret, c) NULL
>> +#define __alloc_from_contiguous(dev, size, prot, ret, c, wv) NULL
>> #define __free_from_pool(cpu_addr, size) 0
>> -#define __free_from_contiguous(dev, page, cpu_addr, size) do { }
>> while (0)
>> +#define __free_from_contiguous(dev, page, cpu_addr, size, wv) do { }
>> while (0)
>> #define __dma_free_remap(cpu_addr, size) do { }
>> while (0)
>>
>> #endif /* CONFIG_MMU */
>> @@ -599,11 +609,13 @@ static void *__alloc_simple_buffer(struct device
>> *dev, size_t size, gfp_t gfp,
>>
>>
>> static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t
>> *handle,
>> - gfp_t gfp, pgprot_t prot, bool is_coherent, const
>> void *caller)
>> + gfp_t gfp, pgprot_t prot, bool is_coherent,
>> + struct dma_attrs *attrs, const void *caller)
>> {
>> u64 mask = get_coherent_dma_mask(dev);
>> struct page *page = NULL;
>> void *addr;
>> + bool want_vaddr;
>>
>> #ifdef CONFIG_DMA_API_DEBUG
>> u64 limit = (mask + 1) & ~mask;
>> @@ -631,20 +643,21 @@ static void *__dma_alloc(struct device *dev, size_t
>> size, dma_addr_t *handle,
>>
>> *handle = DMA_ERROR_CODE;
>> size = PAGE_ALIGN(size);
>> + want_vaddr = !dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING, attrs);
>>
>> if (is_coherent || nommu())
>> addr = __alloc_simple_buffer(dev, size, gfp, &page);
>> else if (!(gfp & __GFP_WAIT))
>> addr = __alloc_from_pool(size, &page);
>> else if (!dev_get_cma_area(dev))
>> - addr = __alloc_remap_buffer(dev, size, gfp, prot, &page,
>> caller);
>> + addr = __alloc_remap_buffer(dev, size, gfp, prot, &page,
>> caller, want_vaddr);
>> else
>> - addr = __alloc_from_contiguous(dev, size, prot, &page,
>> caller);
>> + addr = __alloc_from_contiguous(dev, size, prot, &page,
>> caller, want_vaddr);
>>
>> - if (addr)
>> + if (page)
>> *handle = pfn_to_dma(dev, page_to_pfn(page));
>>
>> - return addr;
>> + return want_vaddr ? addr : &page;
>> }
>>
> What happens if __alloc_remap_buffer or __alloc_from_contiguous fails to
> allocate?
> From this, its seems like we will return &page which will always be non-null
> so it will look like a success.
Good catch. I'll fix it in v2.
Thank you,
--
Carlo Caione
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