linux-kernel - Re: [PATCH v2 2/5] of/address: Introduce of_dma_lower_bus

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Message-ID: <3023eb53ffd2afd8c6c0755af825e426e109cbc2.camel@suse.de>
Date:   Wed, 14 Oct 2020 13:34:47 +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>,
        linux-rpi-kernel@...ts.infradead.org,
        Jeremy Linton <jeremy.linton@....com>,
        iommu@...ts.linux-foundation.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 2/5] of/address: Introduce of_dma_lower_bus_limit()

On Sun, 2020-10-11 at 09:47 +0200, Ard Biesheuvel wrote:
> Hi Nicolas,
> 
> $SUBJECT is out of sync with the patch below. Also, for legibility, it
> helps if the commit log is intelligible by itself, rather than relying
> on $SUBJECT being the first line of the first paragraph.

Noted, I'll update all commit logs.

> On Sat, 10 Oct 2020 at 17:12, Nicolas Saenz Julienne
> <nsaenzjulienne@...e.de> wrote:
> > The function provides the CPU physical address addressable by the most
> > constrained bus in the system. It might be useful in order to
> > dynamically set up memory zones during boot.
> > 
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> > ---
> >  drivers/of/address.c | 34 ++++++++++++++++++++++++++++++++++
> >  include/linux/of.h   |  7 +++++++
> >  2 files changed, 41 insertions(+)
> > 
> > diff --git a/drivers/of/address.c b/drivers/of/address.c
> > index eb9ab4f1e80b..755e97b65096 100644
> > --- a/drivers/of/address.c
> > +++ b/drivers/of/address.c
> > @@ -1024,6 +1024,40 @@ int of_dma_get_range(struct device_node *np, const struct bus_dma_region **map)
> >  }
> >  #endif /* CONFIG_HAS_DMA */
> > 
> > +/**
> > + * of_dma_safe_phys_limit - Get system wide DMA safe address space
> > + *
> > + * Gets the CPU physical address limit for safe DMA addressing system wide by
> > + * searching for the most constraining dma-range. Otherwise it returns ~0ULL.
> > + */
> > +u64 __init of_dma_safe_phys_limit(void)
> 
> I don't think 'safe' strikes the right tone here. You are looking for
> the highest CPU address that is addressable by all DMA masters in the
> system.
> 
> Something like
> 
> of_dma_get_max_cpu_address(void)
> 
> perhaps? Also, since this is generic code, phys_addr_t is probably a
> better type to return.

Sonds good to me, I dindn't like the name I used either.

Will use with phys_addr_t.

Regards,
Nicolas


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