Messages in this thread | | | Date | Wed, 8 Jun 2016 16:01:40 +0800 | From | Jisheng Zhang <> | Subject | Re: [PATCH] arm64: mm: only initialize swiotlb when necessary |
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Dear all,
On Wed, 8 Jun 2016 15:53:46 +0800 Jisheng Zhang wrote:
> we only initialize swiotlb when swiotlb_force is true or not all system > memory is DMA-able, this trivial optimization saves us 64MB when > swiotlb is not necessary.
another solution is to call swiotlb_free() as ppc does. Either solution can solve my problem. If maintainers prefer that solution, I can send a v2 patch.
Thanks, Jisheng
> > Signed-off-by: Jisheng Zhang <jszhang@marvell.com> > --- > arch/arm64/mm/dma-mapping.c | 15 ++++++++++++++- > arch/arm64/mm/init.c | 3 ++- > 2 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c > index c566ec8..46a4157 100644 > --- a/arch/arm64/mm/dma-mapping.c > +++ b/arch/arm64/mm/dma-mapping.c > @@ -19,6 +19,7 @@ > > #include <linux/gfp.h> > #include <linux/acpi.h> > +#include <linux/bootmem.h> > #include <linux/export.h> > #include <linux/slab.h> > #include <linux/genalloc.h> > @@ -29,6 +30,8 @@ > > #include <asm/cacheflush.h> > > +static int swiotlb __read_mostly; > + > static pgprot_t __get_dma_pgprot(struct dma_attrs *attrs, pgprot_t prot, > bool coherent) > { > @@ -341,6 +344,13 @@ static int __swiotlb_get_sgtable(struct device *dev, struct sg_table *sgt, > return ret; > } > > +static int __swiotlb_dma_supported(struct device *hwdev, u64 mask) > +{ > + if (swiotlb) > + return swiotlb_dma_supported(hwdev, mask); > + return 1; > +} > + > static struct dma_map_ops swiotlb_dma_ops = { > .alloc = __dma_alloc, > .free = __dma_free, > @@ -354,7 +364,7 @@ static struct dma_map_ops swiotlb_dma_ops = { > .sync_single_for_device = __swiotlb_sync_single_for_device, > .sync_sg_for_cpu = __swiotlb_sync_sg_for_cpu, > .sync_sg_for_device = __swiotlb_sync_sg_for_device, > - .dma_supported = swiotlb_dma_supported, > + .dma_supported = __swiotlb_dma_supported, > .mapping_error = swiotlb_dma_mapping_error, > }; > > @@ -513,6 +523,9 @@ EXPORT_SYMBOL(dummy_dma_ops); > > static int __init arm64_dma_init(void) > { > + if (swiotlb_force || max_pfn > (arm64_dma_phys_limit >> PAGE_SHIFT)) > + swiotlb = 1; > + > return atomic_pool_init(); > } > arch_initcall(arm64_dma_init); > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index d45f862..7d25b4d 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -403,7 +403,8 @@ static void __init free_unused_memmap(void) > */ > void __init mem_init(void) > { > - swiotlb_init(1); > + if (swiotlb_force || max_pfn > (arm64_dma_phys_limit >> PAGE_SHIFT)) > + swiotlb_init(1); > > set_max_mapnr(pfn_to_page(max_pfn) - mem_map); >
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