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Re: [PATCH V16 08/12] MIPS: Loongson: Add swiotlb to support big memory

To: Huacai Chen <chenhc@lemote.com>
Subject: Re: [PATCH V16 08/12] MIPS: Loongson: Add swiotlb to support big memory (>4GB)
From: Alex Smith <alex.smith@imgtec.com>
Date: Thu, 9 Jan 2014 12:56:50 +0000
Cc: Ralf Baechle <ralf@linux-mips.org>, John Crispin <john@phrozen.org>, "Steven J. Hill" <Steven.Hill@imgtec.com>, Aurelien Jarno <aurelien@aurel32.net>, <linux-mips@linux-mips.org>, Fuxin Zhang <zhangfx@lemote.com>, Zhangjin Wu <wuzhangjin@gmail.com>, Hongliang Tao <taohl@lemote.com>, Hua Yan <yanh@lemote.com>
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On 08/01/14 02:44, Huacai Chen wrote:
This is probably a workaround because Loongson doesn't support DMA
address above 4GB. If memory is more than 4GB, CONFIG_SWIOTLB and
ZONE_DMA32 should be selected. In this way, DMA pages are allocated
below 4GB preferably.

However, CONFIG_SWIOTLB+ZONE_DMA32 is not enough, so, we provide a
platform-specific dma_map_ops::set_dma_mask() to make sure each
driver's dma_mask and coherent_dma_mask is below 32-bit.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Hongliang Tao <taohl@lemote.com>
Signed-off-by: Hua Yan <yanh@lemote.com>
---
  arch/mips/include/asm/dma-mapping.h                |    5 +
  .../mips/include/asm/mach-loongson/dma-coherence.h |   22 +++-
  arch/mips/loongson/common/Makefile                 |    5 +
  arch/mips/loongson/common/dma-swiotlb.c            |  165 ++++++++++++++++++++
  4 files changed, 196 insertions(+), 1 deletions(-)
  create mode 100644 arch/mips/loongson/common/dma-swiotlb.c

diff --git a/arch/mips/include/asm/dma-mapping.h 
b/arch/mips/include/asm/dma-mapping.h
index 84238c5..06412aa 100644
--- a/arch/mips/include/asm/dma-mapping.h
+++ b/arch/mips/include/asm/dma-mapping.h
@@ -49,9 +49,14 @@ static inline int dma_mapping_error(struct device *dev, u64 
mask)
  static inline int
  dma_set_mask(struct device *dev, u64 mask)
  {
+       struct dma_map_ops *ops = get_dma_ops(dev);
+
        if(!dev->dma_mask || !dma_supported(dev, mask))
                return -EIO;

+       if (ops->set_dma_mask)
+               return ops->set_dma_mask(dev, mask);
+
        *dev->dma_mask = mask;

        return 0;
diff --git a/arch/mips/include/asm/mach-loongson/dma-coherence.h 
b/arch/mips/include/asm/mach-loongson/dma-coherence.h
index aeb2c05..6a90275 100644
--- a/arch/mips/include/asm/mach-loongson/dma-coherence.h
+++ b/arch/mips/include/asm/mach-loongson/dma-coherence.h
@@ -11,24 +11,40 @@
  #ifndef __ASM_MACH_LOONGSON_DMA_COHERENCE_H
  #define __ASM_MACH_LOONGSON_DMA_COHERENCE_H

+#ifdef CONFIG_SWIOTLB
+#include <linux/swiotlb.h>
+#endif
+
  struct device;

+extern dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr);
+extern phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr);
  static inline dma_addr_t plat_map_dma_mem(struct device *dev, void *addr,
                                          size_t size)
  {
+#ifdef CONFIG_CPU_LOONGSON3
+       return virt_to_phys(addr);
+#else
        return virt_to_phys(addr) | 0x80000000;
+#endif
  }

  static inline dma_addr_t plat_map_dma_mem_page(struct device *dev,
                                               struct page *page)
  {
+#ifdef CONFIG_CPU_LOONGSON3
+       return page_to_phys(page);
+#else
        return page_to_phys(page) | 0x80000000;
+#endif
  }

  static inline unsigned long plat_dma_addr_to_phys(struct device *dev,
        dma_addr_t dma_addr)
  {
-#if defined(CONFIG_CPU_LOONGSON2F) && defined(CONFIG_64BIT)
+#if defined(CONFIG_CPU_LOONGSON3) && defined(CONFIG_64BIT)
+       return dma_addr;
+#elif defined(CONFIG_CPU_LOONGSON2F) && defined(CONFIG_64BIT)
        return (dma_addr > 0x8fffffff) ? dma_addr : (dma_addr & 0x0fffffff);
  #else
        return dma_addr & 0x7fffffff;
@@ -55,7 +71,11 @@ static inline int plat_dma_supported(struct device *dev, u64 
mask)

  static inline int plat_device_is_coherent(struct device *dev)
  {
+#ifdef CONFIG_DMA_NONCOHERENT
        return 0;
+#else
+       return 1;
+#endif /* CONFIG_DMA_NONCOHERENT */
  }

  #endif /* __ASM_MACH_LOONGSON_DMA_COHERENCE_H */
diff --git a/arch/mips/loongson/common/Makefile 
b/arch/mips/loongson/common/Makefile
index 9e4484c..0bb9cc9 100644
--- a/arch/mips/loongson/common/Makefile
+++ b/arch/mips/loongson/common/Makefile
@@ -26,3 +26,8 @@ obj-$(CONFIG_CS5536) += cs5536/
  #

  obj-$(CONFIG_LOONGSON_SUSPEND) += pm.o
+
+#
+# Big Memory (SWIOTLB) Support
+#
+obj-$(CONFIG_SWIOTLB) += dma-swiotlb.o
diff --git a/arch/mips/loongson/common/dma-swiotlb.c 
b/arch/mips/loongson/common/dma-swiotlb.c
new file mode 100644
index 0000000..9d5451b
--- /dev/null
+++ b/arch/mips/loongson/common/dma-swiotlb.c
@@ -0,0 +1,165 @@
+#include <linux/mm.h>
+#include <linux/init.h>
+#include <linux/dma-mapping.h>
+#include <linux/scatterlist.h>
+#include <linux/swiotlb.h>
+#include <linux/bootmem.h>
+
+#include <asm/bootinfo.h>
+#include <dma-coherence.h>
+
+static void *loongson_dma_alloc_coherent(struct device *dev, size_t size,
+               dma_addr_t *dma_handle, gfp_t gfp, struct dma_attrs *attrs)
+{
+       void *ret;
+
+       if (dma_alloc_from_coherent(dev, size, dma_handle, &ret))
+               return ret;
+
+       /* ignore region specifiers */
+       gfp &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM);
+
+#ifdef CONFIG_ISA
+       if (dev == NULL)
+               gfp |= __GFP_DMA;
+       else
+#endif
+#ifdef CONFIG_ZONE_DMA
+       if (dev->coherent_dma_mask < DMA_BIT_MASK(32))
+               gfp |= __GFP_DMA;
+       else
+#endif
+#ifdef CONFIG_ZONE_DMA32
+        /* Loongson-3 only support DMA in the memory below 4GB now */
+       if (dev->coherent_dma_mask < DMA_BIT_MASK(40))
+               gfp |= __GFP_DMA32;
+       else
+#endif
+       ;
+       gfp |= __GFP_NORETRY;
+
+       ret = swiotlb_alloc_coherent(dev, size, dma_handle, gfp);
+       mb();
+       return ret;
+}
+
+static void loongson_dma_free_coherent(struct device *dev, size_t size,
+               void *vaddr, dma_addr_t dma_handle, struct dma_attrs *attrs)
+{
+       int order = get_order(size);
+
+       if (dma_release_from_coherent(dev, order, vaddr))
+               return;
+
+       swiotlb_free_coherent(dev, size, vaddr, dma_handle);
+}
+
+static dma_addr_t loongson_dma_map_page(struct device *dev, struct page *page,
+                               unsigned long offset, size_t size,
+                               enum dma_data_direction dir,
+                               struct dma_attrs *attrs)
+{
+       dma_addr_t daddr = swiotlb_map_page(dev, page, offset, size,
+                                       dir, attrs);
+       mb();
+       return daddr;
+}
+
+static int loongson_dma_map_sg(struct device *dev, struct scatterlist *sg,
+                               int nents, enum dma_data_direction dir,
+                               struct dma_attrs *attrs)
+{
+       int r = swiotlb_map_sg_attrs(dev, sg, nents, dir, NULL);
+       mb();
+
+       return r;
+}
+
+static void loongson_dma_sync_single_for_device(struct device *dev,
+                               dma_addr_t dma_handle, size_t size,
+                               enum dma_data_direction dir)
+{
+       swiotlb_sync_single_for_device(dev, dma_handle, size, dir);
+       mb();
+}
+
+static void loongson_dma_sync_sg_for_device(struct device *dev,
+                               struct scatterlist *sg, int nents,
+                               enum dma_data_direction dir)
+{
+       swiotlb_sync_sg_for_device(dev, sg, nents, dir);
+       mb();
+}
+
+static dma_addr_t
+loongson_unity_phys_to_dma(struct device *dev, phys_addr_t paddr)
+{
+       return paddr;
+}
+
+static phys_addr_t
+loongson_unity_dma_to_phys(struct device *dev, dma_addr_t daddr)
+{
+       return daddr;
+}
+
+struct loongson_dma_map_ops {
+       struct dma_map_ops dma_map_ops;
+       dma_addr_t (*phys_to_dma)(struct device *dev, phys_addr_t paddr);
+       phys_addr_t (*dma_to_phys)(struct device *dev, dma_addr_t daddr);
+};
+
+dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
+{
+       struct loongson_dma_map_ops *ops = container_of(get_dma_ops(dev),
+                               struct loongson_dma_map_ops, dma_map_ops);
+
+       return ops->phys_to_dma(dev, paddr);
+}
+
+phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr)
+{
+       struct loongson_dma_map_ops *ops = container_of(get_dma_ops(dev),
+                               struct loongson_dma_map_ops, dma_map_ops);
+
+       return ops->dma_to_phys(dev, daddr);
+}

This seems a little bit convoluted. Since phys_to_dma and dma_to_phys will always end up calling the loongson_unity_ functions, I don't see any point in having the loongson_dma_map_ops structure to point to them. You can just implement phys_to_dma and dma_to_phys as inlines in mach-loongson/dma-coherence.h.

Thanks,
Alex

+
+static int loongson_dma_set_mask(struct device *dev, u64 mask)
+{
+       /* Loongson doesn't support DMA above 32-bit */
+       if (mask > DMA_BIT_MASK(32)) {
+               *dev->dma_mask = DMA_BIT_MASK(32);
+               return -EIO;
+       }
+
+       *dev->dma_mask = mask;
+
+       return 0;
+}
+
+static struct loongson_dma_map_ops loongson_linear_dma_map_ops = {
+       .dma_map_ops = {
+               .alloc = loongson_dma_alloc_coherent,
+               .free = loongson_dma_free_coherent,
+               .map_page = loongson_dma_map_page,
+               .unmap_page = swiotlb_unmap_page,
+               .map_sg = loongson_dma_map_sg,
+               .unmap_sg = swiotlb_unmap_sg_attrs,
+               .sync_single_for_cpu = swiotlb_sync_single_for_cpu,
+               .sync_single_for_device = loongson_dma_sync_single_for_device,
+               .sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
+               .sync_sg_for_device = loongson_dma_sync_sg_for_device,
+               .mapping_error = swiotlb_dma_mapping_error,
+               .dma_supported = swiotlb_dma_supported,
+               .set_dma_mask = loongson_dma_set_mask
+       },
+       .phys_to_dma = loongson_unity_phys_to_dma,
+       .dma_to_phys = loongson_unity_dma_to_phys
+};
+
+void __init plat_swiotlb_setup(void)
+{
+       swiotlb_init(1);
+       mips_dma_map_ops = &loongson_linear_dma_map_ops.dma_map_ops;
+}



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