linux-kernel - Re: [PATCH] swiotlb: manipulate orig_addr when tlb

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Date:   Mon, 10 May 2021 10:44:06 +0200
From:   Christoph Hellwig <hch@....de>
To:     Chanho Park <chanho61.park@...sung.com>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Bumyong Lee <bumyong.lee@...sung.com>
Subject: Re: [PATCH] swiotlb: manipulate orig_addr when tlb_addr has offset

On Mon, May 10, 2021 at 05:30:57PM +0900, Chanho Park wrote:
> +static unsigned int swiotlb_align_offset(struct device *dev, u64 addr);

Please just move swiotlb_align_offset up to avoid the forward declaration.

>  /*
>   * Bounce: copy the swiotlb buffer from or back to the original dma location
>   */
> @@ -346,10 +347,17 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
>  	size_t alloc_size = mem->slots[index].alloc_size;
>  	unsigned long pfn = PFN_DOWN(orig_addr);
>  	unsigned char *vaddr = phys_to_virt(tlb_addr);
> +	unsigned int tlb_offset;
>  
>  	if (orig_addr == INVALID_PHYS_ADDR)
>  		return;
>  
> +	tlb_offset = (unsigned int)tlb_addr & (IO_TLB_SIZE - 1);
> +	tlb_offset -= swiotlb_align_offset(dev, orig_addr);

Nit: I'd write this as:

	tlb_offset = (tlb_addr & (IO_TLB_SIZE - 1)) -
			swiotlb_align_offset(dev, orig_addr);

as there is no need for the cast, and just having a single assignment
is easier to follow.