linux-kernel - Re: [PATCH v9 09/14] swiotlb: Refactor swiotlb_tbl_unmap

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Date:   Mon, 14 Jun 2021 08:26:13 +0200
From:   Christoph Hellwig <hch@....de>
To:     Claire Chang <tientzu@...omium.org>
Cc:     Rob Herring <robh+dt@...nel.org>, mpe@...erman.id.au,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        boris.ostrovsky@...cle.com, jgross@...e.com,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        benh@...nel.crashing.org, paulus@...ba.org,
        "list@....net:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        sstabellini@...nel.org, Robin Murphy <robin.murphy@....com>,
        grant.likely@....com, xypron.glpk@....de,
        Thierry Reding <treding@...dia.com>, mingo@...nel.org,
        bauerman@...ux.ibm.com, peterz@...radead.org,
        Greg KH <gregkh@...uxfoundation.org>,
        Saravana Kannan <saravanak@...gle.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        heikki.krogerus@...ux.intel.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-devicetree <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org, xen-devel@...ts.xenproject.org,
        Nicolas Boichat <drinkcat@...omium.org>,
        Jim Quinlan <james.quinlan@...adcom.com>, tfiga@...omium.org,
        bskeggs@...hat.com, bhelgaas@...gle.com, chris@...is-wilson.co.uk,
        daniel@...ll.ch, airlied@...ux.ie, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, jani.nikula@...ux.intel.com,
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        matthew.auld@...el.com, rodrigo.vivi@...el.com,
        thomas.hellstrom@...ux.intel.com
Subject: Re: [PATCH v9 09/14] swiotlb: Refactor swiotlb_tbl_unmap_single

On Fri, Jun 11, 2021 at 11:26:54PM +0800, Claire Chang wrote:
> Add a new function, release_slots, to make the code reusable for supporting
> different bounce buffer pools, e.g. restricted DMA pool.
> 
> Signed-off-by: Claire Chang <tientzu@...omium.org>
> ---
>  kernel/dma/swiotlb.c | 35 ++++++++++++++++++++---------------
>  1 file changed, 20 insertions(+), 15 deletions(-)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 364c6c822063..a6562573f090 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -554,27 +554,15 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
>  	return tlb_addr;
>  }
>  
> -/*
> - * tlb_addr is the physical address of the bounce buffer to unmap.
> - */
> -void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
> -			      size_t mapping_size, enum dma_data_direction dir,
> -			      unsigned long attrs)
> +static void release_slots(struct device *dev, phys_addr_t tlb_addr)
>  {
> -	struct io_tlb_mem *mem = hwdev->dma_io_tlb_mem;
> +	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
>  	unsigned long flags;
> -	unsigned int offset = swiotlb_align_offset(hwdev, tlb_addr);
> +	unsigned int offset = swiotlb_align_offset(dev, tlb_addr);
>  	int index = (tlb_addr - offset - mem->start) >> IO_TLB_SHIFT;
>  	int nslots = nr_slots(mem->slots[index].alloc_size + offset);
>  	int count, i;
>  
> -	/*
> -	 * First, sync the memory before unmapping the entry
> -	 */
> -	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
> -	    (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL))
> -		swiotlb_bounce(hwdev, tlb_addr, mapping_size, DMA_FROM_DEVICE);
> -
>  	/*
>  	 * Return the buffer to the free list by setting the corresponding
>  	 * entries to indicate the number of contiguous entries available.
> @@ -609,6 +597,23 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
>  	spin_unlock_irqrestore(&mem->lock, flags);
>  }
>  
> +/*
> + * tlb_addr is the physical address of the bounce buffer to unmap.
> + */
> +void swiotlb_tbl_unmap_single(struct device *dev, phys_addr_t tlb_addr,
> +			      size_t mapping_size, enum dma_data_direction dir,
> +			      unsigned long attrs)
> +{
> +	/*
> +	 * First, sync the memory before unmapping the entry
> +	 */
> +	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
> +	    (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL))
> +		swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_FROM_DEVICE);
> +
> +	release_slots(dev, tlb_addr);

Can you give this a swiotlb_ prefix?

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@....de>