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

From: Konrad Rzeszutek Wilk <[email-masked]>
Date: Mon, 8 Mar 2010 11:55:00 -0500

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 <[email-masked]>
> CC: [email-masked]
> CC: [email-masked]
> CC: [email-masked]
> CC: [email-masked]
> ---
>  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 *
>  swiotlb_alloc_coherent(struct device *hwdev, size_t size,
>  		       dma_addr_t *dma_handle, gfp_t flags)
> @@ -606,6 +615,8 @@ swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
>  }
>  EXPORT_SYMBOL(swiotlb_free_coherent);
>  
> +#endif /* !CONFIG_NOT_COHERENT_CACHE */
> +
>  static void
>  swiotlb_full(struct device *dev, size_t size, int dir, int do_panic)
>  {
> @@ -652,8 +663,10 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
>  	 * we can safely return the device addr and not worry about bounce
>  	 * buffering it.
>  	 */
> -	if (dma_capable(dev, dev_addr, size) && !swiotlb_force)
> +	if (dma_capable(dev, dev_addr, size) && !swiotlb_force) {
> +		swiotlb_dma_sync_page(page, offset, size, dir);
>  		return dev_addr;
> +	}
>  
>  	/*
>  	 * Oh well, have to allocate and map a bounce buffer.
> @@ -739,6 +752,8 @@ swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
>  		return;
>  	}
>  
> +	swiotlb_dma_sync(phys_to_virt(paddr), size, dir);
> +
>  	if (dir != DMA_FROM_DEVICE)
>  		return;
>  
> @@ -835,8 +850,11 @@ swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems,
>  				return 0;
>  			}
>  			sg->dma_address = swiotlb_virt_to_bus(hwdev, map);
> -		} else
> +		} else {
> +			swiotlb_dma_sync_page(sg_page(sg), sg->offset,
> +					      sg->length, dir);
>  			sg->dma_address = dev_addr;
> +		}
>  		sg->dma_length = sg->length;
>  	}
>  	return nelems;
> -- 
> 1.6.3.3
> 
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