linux-kernel - Re: [PATCH 16/31] s390: handle page-less SG entries

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Message-ID: <alpine.LFD.2.11.1508121350090.1732@denkbrett>
Date:	Wed, 12 Aug 2015 13:51:58 +0200 (CEST)
From:	Sebastian Ott <sebott@...ux.vnet.ibm.com>
To:	Christoph Hellwig <hch@....de>
cc:	torvalds@...ux-foundation.org, axboe@...nel.dk,
	dan.j.williams@...el.com, vgupta@...opsys.com,
	hskinnemoen@...il.com, egtvedt@...fundet.no, realmz6@...il.com,
	dhowells@...hat.com, monstr@...str.eu, x86@...nel.org,
	dwmw2@...radead.org, alex.williamson@...hat.com,
	grundler@...isc-linux.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-alpha@...r.kernel.org,
	linux-ia64@...r.kernel.org, linux-metag@...r.kernel.org,
	linux-mips@...ux-mips.org, linux-parisc@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	sparclinux@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
	linux-nvdimm@...1.01.org, linux-media@...r.kernel.org
Subject: Re: [PATCH 16/31] s390: handle page-less SG entries

On Wed, 12 Aug 2015, Christoph Hellwig wrote:

> Use sg_phys() instead of page_to_phys(sg_page(sg)) so that we don't
> require a page structure for all DMA memory.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

Acked-by: Sebastian Ott <sebott@...ux.vnet.ibm.com>


> ---
>  arch/s390/pci/pci_dma.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
> index 6fd8d58..aae5a47 100644
> --- a/arch/s390/pci/pci_dma.c
> +++ b/arch/s390/pci/pci_dma.c
> @@ -272,14 +272,13 @@ int dma_set_mask(struct device *dev, u64 mask)
>  }
>  EXPORT_SYMBOL_GPL(dma_set_mask);
>  
> -static dma_addr_t s390_dma_map_pages(struct device *dev, struct page *page,
> -				     unsigned long offset, size_t size,
> +static dma_addr_t s390_dma_map_phys(struct device *dev, unsigned long pa,
> +				     size_t size,
>  				     enum dma_data_direction direction,
>  				     struct dma_attrs *attrs)
>  {
>  	struct zpci_dev *zdev = get_zdev(to_pci_dev(dev));
>  	unsigned long nr_pages, iommu_page_index;
> -	unsigned long pa = page_to_phys(page) + offset;
>  	int flags = ZPCI_PTE_VALID;
>  	dma_addr_t dma_addr;
>  
> @@ -301,7 +300,7 @@ static dma_addr_t s390_dma_map_pages(struct device *dev, struct page *page,
>  
>  	if (!dma_update_trans(zdev, pa, dma_addr, size, flags)) {
>  		atomic64_add(nr_pages, &zdev->mapped_pages);
> -		return dma_addr + (offset & ~PAGE_MASK);
> +		return dma_addr + (pa & ~PAGE_MASK);
>  	}
>  
>  out_free:
> @@ -312,6 +311,16 @@ out_err:
>  	return DMA_ERROR_CODE;
>  }
>  
> +static dma_addr_t s390_dma_map_pages(struct device *dev, struct page *page,
> +				     unsigned long offset, size_t size,
> +				     enum dma_data_direction direction,
> +				     struct dma_attrs *attrs)
> +{
> +	unsigned long pa = page_to_phys(page) + offset;
> +
> +	return s390_dma_map_phys(dev, pa, size, direction, attrs);
> +}
> +
>  static void s390_dma_unmap_pages(struct device *dev, dma_addr_t dma_addr,
>  				 size_t size, enum dma_data_direction direction,
>  				 struct dma_attrs *attrs)
> @@ -384,8 +393,7 @@ static int s390_dma_map_sg(struct device *dev, struct scatterlist *sg,
>  	int i;
>  
>  	for_each_sg(sg, s, nr_elements, i) {
> -		struct page *page = sg_page(s);
> -		s->dma_address = s390_dma_map_pages(dev, page, s->offset,
> +		s->dma_address = s390_dma_map_phys(dev, sg_phys(s),
>  						    s->length, dir, NULL);
>  		if (!dma_mapping_error(dev, s->dma_address)) {
>  			s->dma_length = s->length;
> -- 
> 1.9.1
> 
> --
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