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Date: Sat, 09 Oct 2010 10:44:53 +1100
From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
To: Nishanth Aravamudan <nacc@...ibm.com>
Cc: miltonm@....com, Paul Mackerras <paulus@...ba.org>,
Andrew Morton <akpm@...ux-foundation.org>,
FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
Kumar Gala <galak@...nel.crashing.org>,
Scott Wood <scottwood@...escale.com>,
Anton Vorontsov <avorontsov@...sta.com>,
linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 03/11] ppc: Create ops to choose between direct
window and iommu based on device mask
On Fri, 2010-10-08 at 10:33 -0700, Nishanth Aravamudan wrote:
> Also allow the coherent ops to be iommu if only the coherent mask is too
> small, mostly for driver that do not set set the coherent mask but also
> don't use the coherent api.
You are doing the transition at map_sg time which is a hot path, I don't
like that. Also you add all those "choose" variants of the dma ops...
not very nice at all.
You may want to look at the patches I posted to the list a while back
for doing direct DMA on Bimini:
[PATCH 1/2] powerpc/dma: Add optional platform override of dma_set_mask()
[PATCH 2/2] powerpc/dart_iommu: Support for 64-bit iommu bypass window on PCIe
Cheers,
Ben.
> Signed-off-by: Milton Miller <miltonm@....com>
> Signed-off-by: Nishanth Aravamudan <nacc@...ibm.com>
> ---
> arch/powerpc/include/asm/dma-mapping.h | 2 +
> arch/powerpc/kernel/Makefile | 2 +-
> arch/powerpc/kernel/dma-choose64.c | 167 ++++++++++++++++++++++++++++++++
> 3 files changed, 170 insertions(+), 1 deletions(-)
> create mode 100644 arch/powerpc/kernel/dma-choose64.c
>
> diff --git a/arch/powerpc/include/asm/dma-mapping.h b/arch/powerpc/include/asm/dma-mapping.h
> index 644103a..9ffb16a 100644
> --- a/arch/powerpc/include/asm/dma-mapping.h
> +++ b/arch/powerpc/include/asm/dma-mapping.h
> @@ -68,6 +68,8 @@ static inline unsigned long device_to_mask(struct device *dev)
> */
> #ifdef CONFIG_PPC64
> extern struct dma_map_ops dma_iommu_ops;
> +extern struct dma_map_ops dma_choose64_ops;
> +extern struct dma_map_ops dma_iommu_coherent_ops;
> #endif
> extern struct dma_map_ops dma_direct_ops;
>
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index 1dda701..21b8ea1 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -82,7 +82,7 @@ obj-y += time.o prom.o traps.o setup-common.o \
> udbg.o misc.o io.o dma.o \
> misc_$(CONFIG_WORD_SIZE).o
> obj-$(CONFIG_PPC32) += entry_32.o setup_32.o
> -obj-$(CONFIG_PPC64) += dma-iommu.o iommu.o
> +obj-$(CONFIG_PPC64) += dma-iommu.o iommu.o dma-choose64.o
> obj-$(CONFIG_KGDB) += kgdb.o
> obj-$(CONFIG_PPC_OF_BOOT_TRAMPOLINE) += prom_init.o
> obj-$(CONFIG_MODULES) += ppc_ksyms.o
> diff --git a/arch/powerpc/kernel/dma-choose64.c b/arch/powerpc/kernel/dma-choose64.c
> new file mode 100644
> index 0000000..17c716f
> --- /dev/null
> +++ b/arch/powerpc/kernel/dma-choose64.c
> @@ -0,0 +1,167 @@
> +/*
> + * Copyright (C) 2006 Benjamin Herrenschmidt, IBM Corporation
> + *
> + * Provide default implementations of the DMA mapping callbacks for
> + * directly mapped busses.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/bug.h>
> +
> +/*
> + * DMA operations that choose between a 64-bit direct mapping and and iommu
> + *
> + * This set of dma ops chooses between directing to a static 1:1 mapping
> + * that may require a 64 bit address and a iommu based on the declared
> + * streaming and coherent masks for the device. The choice is made on
> + * the first dma map call.
> + */
> +
> +/* first BUG ops for calls out of sequence */
> +
> +void *dma_bug_alloc_coherent(struct device *dev, size_t size,
> + dma_addr_t *dma_handle, gfp_t flag)
> +{
> + BUG();
> +
> + return NULL;
> +}
> +
> +void dma_bug_free_coherent(struct device *dev, size_t size,
> + void *vaddr, dma_addr_t dma_handle)
> +{
> + BUG();
> +}
> +
> +static int dma_bug_dma_supported(struct device *dev, u64 mask)
> +{
> + BUG();
> +
> + return 0;
> +}
> +
> +static int dma_bug_map_sg(struct device *dev, struct scatterlist *sgl,
> + int nents, enum dma_data_direction direction,
> + struct dma_attrs *attrs)
> +{
> + BUG();
> +
> + return 0;
> +}
> +
> +
> +static void dma_bug_unmap_sg(struct device *dev, struct scatterlist *sg,
> + int nents, enum dma_data_direction direction,
> + struct dma_attrs *attrs)
> +{
> + BUG();
> +}
> +
> +static dma_addr_t dma_bug_map_page(struct device *dev,
> + struct page *page,
> + unsigned long offset,
> + size_t size,
> + enum dma_data_direction dir,
> + struct dma_attrs *attrs)
> +{
> + BUG();
> +
> + return DMA_ERROR_CODE;
> +}
> +
> +
> +static void dma_bug_unmap_page(struct device *dev,
> + dma_addr_t dma_address,
> + size_t size,
> + enum dma_data_direction direction,
> + struct dma_attrs *attrs)
> +{
> + BUG();
> +}
> +
> +
> +static struct dma_map_ops *choose(struct device *dev)
> +{
> + if (dma_direct_ops.dma_supported(dev, device_to_mask(dev))) {
> + if (dma_direct_ops.dma_supported(dev, dev->coherent_dma_mask))
> + return &dma_direct_ops;
> + return &dma_iommu_coherent_ops;
> + }
> + return &dma_iommu_ops;
> +}
> +
> +void *dma_choose64_alloc_coherent(struct device *dev, size_t size,
> + dma_addr_t *dma_handle, gfp_t flag)
> +{
> + struct dma_map_ops *new = choose(dev);
> +
> + set_dma_ops(dev, new);
> + return new->alloc_coherent(dev, size, dma_handle, flag);
> +}
> +
> +static int dma_choose64_map_sg(struct device *dev, struct scatterlist *sgl,
> + int nents, enum dma_data_direction direction,
> + struct dma_attrs *attrs)
> +{
> + struct dma_map_ops *new = choose(dev);
> +
> + set_dma_ops(dev, new);
> + return new->map_sg(dev, sgl, nents, direction, attrs);
> +}
> +
> +
> +static int dma_choose64_dma_supported(struct device *dev, u64 mask)
> +{
> + return dma_direct_ops.dma_supported(dev, mask) ||
> + dma_iommu_ops.dma_supported(dev, mask);
> +}
> +
> +static dma_addr_t dma_choose64_map_page(struct device *dev,
> + struct page *page,
> + unsigned long offset,
> + size_t size,
> + enum dma_data_direction dir,
> + struct dma_attrs *attrs)
> +{
> + struct dma_map_ops *new = choose(dev);
> +
> + set_dma_ops(dev, new);
> + return new->map_page(dev, page, offset, size, dir, attrs);
> +}
> +
> +struct dma_map_ops dma_choose64_ops = {
> + .alloc_coherent = dma_choose64_alloc_coherent,
> + .free_coherent = dma_bug_free_coherent,
> + .map_sg = dma_choose64_map_sg,
> + .unmap_sg = dma_bug_unmap_sg,
> + .dma_supported = dma_choose64_dma_supported,
> + .map_page = dma_choose64_map_page,
> + .unmap_page = dma_bug_unmap_page,
> +};
> +EXPORT_SYMBOL(dma_choose64_ops);
> +
> +/* set these up to BUG() until we initialze them in the arch initcall below */
> +struct dma_map_ops dma_iommu_coherent_ops = {
> + .alloc_coherent = dma_bug_alloc_coherent,
> + .free_coherent = dma_bug_free_coherent,
> + .map_sg = dma_bug_map_sg,
> + .unmap_sg = dma_bug_unmap_sg,
> + .dma_supported = dma_bug_dma_supported,
> + .map_page = dma_bug_map_page,
> + .unmap_page = dma_bug_unmap_page,
> +};
> +EXPORT_SYMBOL(dma_iommu_coherent_ops);
> +
> +static int setup_choose64_ops(void)
> +{
> + dma_iommu_coherent_ops = dma_direct_ops;
> + dma_iommu_coherent_ops.alloc_coherent = dma_iommu_ops.alloc_coherent;
> + dma_iommu_coherent_ops.free_coherent = dma_iommu_ops.free_coherent;
> +
> + /* should we be stricter? */
> + dma_iommu_coherent_ops.dma_supported = dma_choose64_dma_supported;
> +
> + return 0;
> +}
> +arch_initcall(setup_choose64_ops);
--
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