Re: [LKML] [RFC PATCH v3 04/11] swiotlb: support NOT_COHERENT_CACHE PowerPC platforms

[Albert Herranz]

Konrad Rzeszutek Wilk wrote:
 Hey Albert,
 
 I've been doing some posting in this area to split the physical / bus
 address translation so that multiple platforms can utilize it. I was
 wondering if it makes sense to utilize some of those concepts (ie, extend it
 for DMA coherency) for your code:
 
 https://lists.linux-foundation.org/pipermail/iommu/2010-February/002066.html
 
 And here is the git tree that goes on top of those patches:
 git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb-2.6.git 
 xen-swiotlb-0.5
 

Hi Konrad,

Thanks for your comments.

In my case, I'd like to re-use as much code from swiotlb as possible.
Adding a few function calls at strategic spots (which are optimized out for 
cache coherent platforms) to maintain cache coherency is currently enough for 
me if that's acceptable.
A more general approach would involve making swiotlb_bounce() 
platform-dependent (or at least the actual code for copying the buffers), and 
re-implementing map_page, sync_single and map_sg at the platform DMA code again.

I've whipped through your patches. If I undestood them, you make available a 
kind of swiotlb library core on top of which you can build alternate 
swiotlb-based dma ops.
Wouldn't it be a good idea to split the library code from the default swiotlb 
dma ops?
A(n embedded) platform may just want the library code to implement its own 
dma ops, without having to pay for the extra default swiotlb dma ops 
implementation.

Thanks,
Albert

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Re: [LKML] [RFC PATCH v3 04/11] swiotlb: support NOT_COHERENT_CACHE PowerPC platforms

[Konrad Rzeszutek Wilk]

On Sun, Mar 07, 2010 at 01:11:45PM +0100, Albert Herranz wrote:
 The current SWIOTLB code does not support NOT_COHERENT_CACHE platforms.
 This patch adds support for NOT_COHERENT_CACHE platforms to SWIOTLB by
 adding two platform specific functions swiotlb_dma_sync_page() and
 swiotlb_dma_sync() which can be used to explicitly manage cache coherency.

Hey Albert,

I've been doing some posting in this area to split the physical / bus
address translation so that multiple platforms can utilize it. I was
wondering if it makes sense to utilize some of those concepts (ie, extend it
for DMA coherency) for your code:

https://lists.linux-foundation.org/pipermail/iommu/2010-February/002066.html

And here is the git tree that goes on top of those patches:
git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb-2.6.git 
xen-swiotlb-0.5


 
 On PowerPC these functions are mapped to their corresponding
 __dma_sync_page() and __dma_sync() functions.
 On other architectures using SWIOTLB these functions are optimized out.
 
 This will be used later to support SWIOTLB on the Nintendo Wii video game
 console.
 
 Signed-off-by: Albert Herranz albert_herr...@yahoo.es
 CC: linuxppc-dev@lists.ozlabs.org
 CC: linux-ker...@vger.kernel.org
 CC: x...@kernel.org
 CC: linux-i...@vger.kernel.org
 ---
  arch/ia64/include/asm/swiotlb.h|   10 ++
  arch/powerpc/include/asm/swiotlb.h |3 +++
  arch/x86/include/asm/swiotlb.h |   10 ++
  lib/swiotlb.c  |   30 --
  4 files changed, 47 insertions(+), 6 deletions(-)
 
 diff --git a/arch/ia64/include/asm/swiotlb.h b/arch/ia64/include/asm/swiotlb.h
 index f0acde6..6722090 100644
 --- a/arch/ia64/include/asm/swiotlb.h
 +++ b/arch/ia64/include/asm/swiotlb.h
 @@ -14,4 +14,14 @@ static inline void pci_swiotlb_init(void)
  }
  #endif
  
 +static inline void swiotlb_dma_sync_page(struct page *page,
 +  unsigned long offset,
 +  size_t size, int direction)
 +{
 +}
 +
 +static inline void swiotlb_dma_sync(void *vaddr, size_t size, int direction)
 +{
 +}
 +
  #endif /* ASM_IA64__SWIOTLB_H */
 diff --git a/arch/powerpc/include/asm/swiotlb.h 
 b/arch/powerpc/include/asm/swiotlb.h
 index 8979d4c..603b343 100644
 --- a/arch/powerpc/include/asm/swiotlb.h
 +++ b/arch/powerpc/include/asm/swiotlb.h
 @@ -22,4 +22,7 @@ int __init swiotlb_setup_bus_notifier(void);
  
  extern void pci_dma_dev_setup_swiotlb(struct pci_dev *pdev);
  
 +#define swiotlb_dma_sync_page __dma_sync_page
 +#define swiotlb_dma_sync __dma_sync
 +
  #endif /* __ASM_SWIOTLB_H */
 diff --git a/arch/x86/include/asm/swiotlb.h b/arch/x86/include/asm/swiotlb.h
 index 8085277..e5f6d9c 100644
 --- a/arch/x86/include/asm/swiotlb.h
 +++ b/arch/x86/include/asm/swiotlb.h
 @@ -20,4 +20,14 @@ static inline void pci_swiotlb_init(void)
  
  static inline void dma_mark_clean(void *addr, size_t size) {}
  
 +static inline void swiotlb_dma_sync_page(struct page *page,
 +  unsigned long offset,
 +  size_t size, int direction)
 +{
 +}
 +
 +static inline void swiotlb_dma_sync(void *vaddr, size_t size, int direction)
 +{
 +}
 +
  #endif /* _ASM_X86_SWIOTLB_H */
 diff --git a/lib/swiotlb.c b/lib/swiotlb.c
 index 94db5df..8f2dad9 100644
 --- a/lib/swiotlb.c
 +++ b/lib/swiotlb.c
 @@ -346,10 +346,13 @@ static void swiotlb_bounce(phys_addr_t phys, char 
 *dma_addr, size_t size,
   local_irq_save(flags);
   buffer = kmap_atomic(pfn_to_page(pfn),
KM_BOUNCE_READ);
 - if (dir == DMA_TO_DEVICE)
 + if (dir == DMA_TO_DEVICE) {
   memcpy(dma_addr, buffer + offset, sz);
 - else
 + swiotlb_dma_sync(dma_addr, sz, dir);
 + } else {
 + swiotlb_dma_sync(dma_addr, sz, dir);
   memcpy(buffer + offset, dma_addr, sz);
 + }
   kunmap_atomic(buffer, KM_BOUNCE_READ);
   local_irq_restore(flags);
  
 @@ -359,10 +362,14 @@ static void swiotlb_bounce(phys_addr_t phys, char 
 *dma_addr, size_t size,
   offset = 0;
   }
   } else {
 - if (dir == DMA_TO_DEVICE)
 + if (dir == DMA_TO_DEVICE) {
   memcpy(dma_addr, phys_to_virt(phys), size);
 - else
 + swiotlb_dma_sync(dma_addr, size, dir);
 +
 + } else {
 + swiotlb_dma_sync(dma_addr, size, dir);
   memcpy(phys_to_virt(phys), dma_addr, size);
 + }
   }
  }
  
 @@ -542,6 +549,8 @@ sync_single(struct device *hwdev, char *dma_addr, size_t 
 size,
   }
  }
  
 +#ifndef CONFIG_NOT_COHERENT_CACHE
 +
  void *