linux-kernel - Re: [PATCH v4 3/7] of/address: Introduce of_dma_get_max_cpu

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Message-ID: <e1da254cdf27edb3de798058bb234d8ded80267b.camel@suse.de>
Date:   Thu, 22 Oct 2020 16:03:16 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Christoph Hellwig <hch@....de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Robin Murphy <robin.murphy@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Linux IOMMU <iommu@...ts.linux-foundation.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Will Deacon <will@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Hanjun Guo <guohanjun@...wei.com>
Subject: Re: [PATCH v4 3/7] of/address: Introduce
 of_dma_get_max_cpu_address()

On Thu, 2020-10-22 at 14:23 +0200, Ard Biesheuvel wrote:
> > +/**
> > + * of_dma_get_max_cpu_address - Gets highest CPU address suitable for DMA
> > + * @np: The node to start searching from or NULL to start from the root
> > + *
> > + * Gets the highest CPU physical address that is addressable by all DMA masters
> > + * in the sub-tree pointed by np, or the whole tree if NULL is passed. If no
> > + * DMA constrained device is found, it returns PHYS_ADDR_MAX.
> > + */
> > +phys_addr_t __init of_dma_get_max_cpu_address(struct device_node *np)
> > +{
> > +       phys_addr_t max_cpu_addr = PHYS_ADDR_MAX;
> > +       struct of_range_parser parser;
> > +       phys_addr_t subtree_max_addr;
> > +       struct device_node *child;
> > +       struct of_range range;
> > +       const __be32 *ranges;
> > +       u64 cpu_end = 0;
> > +       int len;
> > +
> > +       if (!np)
> > +               np = of_root;
> > +
> > +       ranges = of_get_property(np, "dma-ranges", &len);
> > +       if (ranges && len) {
> > +               of_dma_range_parser_init(&parser, np);
> > +               for_each_of_range(&parser, &range)
> > +                       if (range.cpu_addr + range.size > cpu_end)
> > +                               cpu_end = range.cpu_addr + range.size;
> 
> 
> Shouldn't this be 'range.cpu_addr + range.size - 1' ?

Yes, I agree. In that case arm64's counterpart should be:

	zone_dma_bits = max(32U, fls64(of_dma_get_max_cpu_address(NULL)));

I'll update it.

Regards,
Nicolas


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