linux-kernel - Re: [PATCH 1/2] dma-mapping: introduce dma_get_seg_boundary_nr

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Date:   Thu, 03 Sep 2020 13:47:43 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Nicolin Chen <nicoleotsuka@...il.com>, hch@....de
Cc:     sfr@...b.auug.org.au, benh@...nel.crashing.org, paulus@...ba.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        rth@...ddle.net, ink@...assic.park.msu.ru, mattst88@...il.com,
        linux-alpha@...r.kernel.org, tony.luck@...el.com,
        fenghua.yu@...el.com, linux-ia64@...r.kernel.org,
        schnelle@...ux.ibm.com, gerald.schaefer@...ux.ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com, borntraeger@...ibm.com,
        linux-s390@...r.kernel.org, davem@...emloft.net,
        sparclinux@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        James.Bottomley@...senPartnership.com, deller@....de,
        linux-parisc@...r.kernel.org
Subject: Re: [PATCH 1/2] dma-mapping: introduce dma_get_seg_boundary_nr_pages()

Nicolin Chen <nicoleotsuka@...il.com> writes:
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index 9704f3f76e63..cbc2e62db597 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -236,15 +236,10 @@ static unsigned long iommu_range_alloc(struct device *dev,
>  		}
>  	}
>  
> -	if (dev)
> -		boundary_size = ALIGN(dma_get_seg_boundary(dev) + 1,
> -				      1 << tbl->it_page_shift);
> -	else
> -		boundary_size = ALIGN(1UL << 32, 1 << tbl->it_page_shift);
> -	/* 4GB boundary for iseries_hv_alloc and iseries_hv_map */
> +	boundary_size = dma_get_seg_boundary_nr_pages(dev, tbl->it_page_shift);
>  
>  	n = iommu_area_alloc(tbl->it_map, limit, start, npages, tbl->it_offset,
> -			     boundary_size >> tbl->it_page_shift, align_mask);
> +			     boundary_size, align_mask);

This has changed the units of boundary_size, but it's unused elsewhere
in the function so that's OK.

If you need to do a v2 for any other reason, then I'd just drop
boundary_size and call dma_get_seg_boundary_nr_pages() directly in the
function call.

Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)

cheers