From: Catalin Marinas <catalin.marinas@arm.com>
To: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: f.fainelli@gmail.com, mbrugger@suse.com, marc.zyngier@arm.com,
robin.murphy@arm.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, robh+dt@kernel.org, wahrenst@gmx.net,
m.szyprowski@samsung.com, linux-riscv@lists.infradead.org,
phill@raspberrypi.org, Will Deacon <will@kernel.org>,
hch@lst.de, linux-arm-kernel@lists.infradead.org,
linux-rpi-kernel@lists.infradead.org
Subject: Re: [PATCH v5 3/4] arm64: use both ZONE_DMA and ZONE_DMA32
Date: Wed, 11 Sep 2019 15:35:27 +0100 [thread overview]
Message-ID: <20190911143527.GB43864@C02TF0J2HF1T.local> (raw)
In-Reply-To: <b0b824bebb9ef13ce746f9914de83126b0386e23.camel@suse.de>
On Wed, Sep 11, 2019 at 12:54:38PM +0200, Nicolas Saenz Julienne wrote:
> On Mon, 2019-09-09 at 11:58 +0200, Nicolas Saenz Julienne wrote:
> > /*
> > - * Return the maximum physical address for ZONE_DMA32 (DMA_BIT_MASK(32)). It
> > - * currently assumes that for memory starting above 4G, 32-bit devices will
> > - * use a DMA offset.
> > + * Return the maximum physical address for a zone with a given address size
> > + * limit. It currently assumes that for memory starting above 4G, 32-bit
> > + * devices will use a DMA offset.
> > */
> > -static phys_addr_t __init max_zone_dma32_phys(void)
> > +static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
> > {
> > phys_addr_t offset = memblock_start_of_DRAM() & GENMASK_ULL(63, 32);
> > - return min(offset + (1ULL << 32), memblock_end_of_DRAM());
> > + return min(offset + (1ULL << zone_bits), memblock_end_of_DRAM());
> > }
>
> while testing other code on top of this series on odd arm64 machines I found an
> issue: when memblock_start_of_DRAM() != 0, max_zone_phys() isn't taking into
> account the offset to the beginning of memory. This doesn't matter with
> zone_bits == 32 but it does when zone_bits == 30.
I thought about this but I confused myself and the only case I had in
mind was an AMD Seattle system with RAM starting at 4GB.
What we need from this function is that the lowest naturally aligned
2^30 RAM is covered by ZONE_DMA while the rest to 2^32 are ZONE_DMA32.
This assumed that devices only capable of 30-bit (or 32-bit), have the
top address bits hardwired to be able access the bottom of the memory
(and this would be expressed in DT as the DMA offset).
I guess the fix here is to use GENMASK_ULL(63, zone_bits).
--
Catalin
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next prev parent reply other threads:[~2019-09-11 14:35 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-09 9:58 [PATCH v5 0/4] Raspberry Pi 4 DMA addressing support Nicolas Saenz Julienne
2019-09-09 9:58 ` [PATCH v5 1/4] arm64: mm: use arm64_dma_phys_limit instead of calling max_zone_dma_phys() Nicolas Saenz Julienne
2019-09-09 9:58 ` [PATCH v5 2/4] arm64: rename variables used to calculate ZONE_DMA32's size Nicolas Saenz Julienne
2019-09-09 9:58 ` [PATCH v5 3/4] arm64: use both ZONE_DMA and ZONE_DMA32 Nicolas Saenz Julienne
2019-09-11 10:54 ` Nicolas Saenz Julienne
2019-09-11 14:35 ` Catalin Marinas [this message]
2019-09-11 15:00 ` Nicolas Saenz Julienne
2019-09-09 9:58 ` [PATCH v5 4/4] mm: refresh ZONE_DMA and ZONE_DMA32 comments in 'enum zone_type' Nicolas Saenz Julienne
2019-09-09 19:33 ` [PATCH v5 0/4] Raspberry Pi 4 DMA addressing support Stefan Wahren
2019-09-09 19:50 ` Nicolas Saenz Julienne
2019-09-10 9:27 ` Matthias Brugger
2019-09-12 17:18 ` Matthias Brugger
2019-09-12 17:27 ` Florian Fainelli
2019-09-12 19:32 ` Stefan Wahren
2019-09-13 7:15 ` Matthias Brugger
2019-09-13 8:09 ` Matthias Brugger
2019-09-13 8:50 ` Stefan Wahren
2019-09-13 9:25 ` Matthias Brugger
2019-09-13 10:08 ` Stefan Wahren
2019-09-13 10:39 ` Matthias Brugger
2019-09-16 19:19 ` Stefan Wahren
2019-09-17 9:04 ` Matthias Brugger
2019-09-17 18:03 ` Stefan Wahren
2019-09-27 16:44 ` Stefan Wahren
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