From: lauraa@codeaurora.org (Laura Abbott)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCHv4 3/5] common: dma-mapping: Introduce common remapping functions
Date: Wed, 23 Jul 2014 14:56:11 -0700 [thread overview]
Message-ID: <53D02F7B.5020309@codeaurora.org> (raw)
In-Reply-To: <20140723104554.GB1366@localhost>
On 7/23/2014 3:45 AM, Catalin Marinas wrote:
> On Wed, Jul 23, 2014 at 02:35:06AM +0100, Laura Abbott wrote:
>> --- a/arch/arm/mm/dma-mapping.c
>> +++ b/arch/arm/mm/dma-mapping.c
>> @@ -298,37 +298,19 @@ static void *
>> __dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
>> const void *caller)
>> {
>> - struct vm_struct *area;
>> - unsigned long addr;
>> -
>> /*
>> * DMA allocation can be mapped to user space, so lets
>> * set VM_USERMAP flags too.
>> */
>> - area = get_vm_area_caller(size, VM_ARM_DMA_CONSISTENT | 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;
>> + return dma_common_contiguous_remap(page, size,
>> + VM_ARM_DMA_CONSISTENT | VM_USERMAP,
>> + prot, caller);
>
> I think we still need at least a comment in the commit log since the arm
> code is moving from ioremap_page_range() to map_vm_area(). There is a
> slight performance penalty with the addition of a kmalloc() on this
> path.
>
> Or even better (IMO), see below.
>
>> --- a/drivers/base/dma-mapping.c
>> +++ b/drivers/base/dma-mapping.c
> [...]
>> +void *dma_common_contiguous_remap(struct page *page, size_t size,
>> + unsigned long vm_flags,
>> + pgprot_t prot, const void *caller)
>> +{
>> + int i;
>> + struct page **pages;
>> + void *ptr;
>> +
>> + pages = kmalloc(sizeof(struct page *) << get_order(size), GFP_KERNEL);
>> + if (!pages)
>> + return NULL;
>> +
>> + for (i = 0; i < (size >> PAGE_SHIFT); i++)
>> + pages[i] = page + i;
>> +
>> + ptr = dma_common_pages_remap(pages, size, vm_flags, prot, caller);
>> +
>> + kfree(pages);
>> +
>> + return ptr;
>> +}
>
> You could avoid the dma_common_page_remap() here (and kmalloc) and
> simply use ioremap_page_range(). We know that
> dma_common_contiguous_remap() is only called with contiguous physical
> range, so ioremap_page_range() is suitable. It also makes it a
> non-functional change for arch/arm.
>
My original thought with using map_vm_area vs. ioremap_page_range was
that ioremap_page_range is really intended for mapping io devices and
the like into the kernel virtual address space. map_vm_area is designed
to handle pages of kernel managed memory. Perhaps it's too nit-picky
a distinction though.
Thanks,
Laura
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
next prev parent reply other threads:[~2014-07-23 21:56 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-23 1:35 [PATCHv4 0/5] Atomic pool for arm64 Laura Abbott
2014-07-23 1:35 ` [PATCHv4 1/5] lib/genalloc.c: Add power aligned algorithm Laura Abbott
2014-07-23 1:35 ` [PATCHv4 2/5] lib/genalloc.c: Add genpool range check function Laura Abbott
2014-07-23 1:35 ` [PATCHv4 3/5] common: dma-mapping: Introduce common remapping functions Laura Abbott
2014-07-23 10:45 ` Catalin Marinas
2014-07-23 21:56 ` Laura Abbott [this message]
2014-07-24 13:52 ` Catalin Marinas
2014-07-23 11:16 ` Catalin Marinas
2014-07-23 1:35 ` [PATCHv4 4/5] arm: use genalloc for the atomic pool Laura Abbott
2014-07-23 1:35 ` [PATCHv4 5/5] arm64: Add atomic pool for non-coherent and CMA allocations Laura Abbott
2014-07-24 13:56 ` [PATCHv4 0/5] Atomic pool for arm64 Catalin Marinas
-- strict thread matches above, loose matches on Subject: below --
2014-07-02 18:03 [PATCHv4 0/5] DMA " Laura Abbott
2014-07-02 18:03 ` [PATCHv4 3/5] common: dma-mapping: Introduce common remapping functions Laura Abbott
2014-07-09 22:46 ` Olof Johansson
2014-07-18 14:13 ` Catalin Marinas
2014-07-18 13:53 ` Catalin Marinas
2014-07-21 19:33 ` Laura Abbott
2014-07-22 16:04 ` Catalin Marinas
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