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From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Qian Cai <cai@lca.pw>
Cc: linux-rpi-kernel@lists.infradead.org, f.fainelli@gmail.com,
	will@kernel.org, marc.zyngier@arm.com, catalin.marinas@arm.com,
	linux-kernel@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
	linux-mm@kvack.org, mbrugger@suse.com, wahrenst@gmx.net,
	phill@raspberrypi.org, robin.murphy@arm.com,
	Christoph Hellwig <hch@lst.de>,
	linux-arm-kernel@lists.infradead.org, m.szyprowski@samsung.com
Subject: Re: [PATCH v6 3/4] arm64: use both ZONE_DMA and ZONE_DMA32
Date: Mon, 21 Oct 2019 16:34:58 +0200
Message-ID: <78caa5bcfc0d59e8ec5d6b7060df76896d25248b.camel@suse.de> (raw)
In-Reply-To: <3956E54B-6C7A-4C47-B9B6-75F556EFD3F5@lca.pw>

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On Mon, 2019-10-21 at 10:15 -0400, Qian Cai wrote:
> > On Sep 11, 2019, at 2:25 PM, Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> > wrote:
> > 
> > So far all arm64 devices have supported 32 bit DMA masks for their
> > peripherals. This is not true anymore for the Raspberry Pi 4 as most of
> > it's peripherals can only address the first GB of memory on a total of
> > up to 4 GB.
> > 
> > This goes against ZONE_DMA32's intent, as it's expected for ZONE_DMA32
> > to be addressable with a 32 bit mask. So it was decided to re-introduce
> > ZONE_DMA in arm64.
> > 
> > ZONE_DMA will contain the lower 1G of memory, which is currently the
> > memory area addressable by any peripheral on an arm64 device.
> > ZONE_DMA32 will contain the rest of the 32 bit addressable memory.
> > 
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> > 
> > ---
> 
> With ZONE_DMA=y, this config will fail to reserve 512M CMA on a server,
> 
> https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config
> 
> CONFIG_DMA_CMA=y
> CONFIG_CMA_SIZE_MBYTES=64
> CONFIG_CMA_SIZE_SEL_MBYTES=y
> CONFIG_CMA_ALIGNMENT=8
> CONFIG_CMA=y
> CONFIG_CMA_DEBUGFS=y
> CONFIG_CMA_AREAS=7
> 
> Is this expected?

Not really, just tested cma=512M on a Raspberry Pi4, and it went well. The only
thing on my build that differs from your config is CONFIG_CMA_DEBUGFS.

Could you post more information on the device you're experiencing this on? Also
some logs.

Regards,
Nicolas


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Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-11 18:25 [PATCH v6 0/4] Raspberry Pi 4 DMA addressing support Nicolas Saenz Julienne
2019-09-11 18:25 ` [PATCH v6 1/4] arm64: mm: use arm64_dma_phys_limit instead of calling max_zone_dma_phys() Nicolas Saenz Julienne
2019-09-11 18:25 ` [PATCH v6 2/4] arm64: rename variables used to calculate ZONE_DMA32's size Nicolas Saenz Julienne
2019-09-11 18:25 ` [PATCH v6 3/4] arm64: use both ZONE_DMA and ZONE_DMA32 Nicolas Saenz Julienne
2019-10-21 14:15   ` Qian Cai
2019-10-21 14:34     ` Nicolas Saenz Julienne [this message]
2019-10-21 14:46       ` Qian Cai
2019-10-21 17:01         ` Nicolas Saenz Julienne
2019-10-21 17:25           ` Qian Cai
2019-10-21 17:55             ` Nicolas Saenz Julienne
2019-10-21 20:36               ` Qian Cai
2019-10-22 11:23                 ` Nicolas Saenz Julienne
2019-10-23  7:11                   ` Matthias Brugger
2019-10-31 15:51                   ` Catalin Marinas
2019-10-31 16:04                     ` Nicolas Saenz Julienne
2019-10-31 18:02                       ` Catalin Marinas
2019-10-31 18:11                         ` Nicolas Saenz Julienne
2019-10-31 18:13                           ` Catalin Marinas
2019-09-11 18:25 ` [PATCH v6 4/4] mm: refresh ZONE_DMA and ZONE_DMA32 comments in 'enum zone_type' Nicolas Saenz Julienne
2019-10-01 16:05 ` [PATCH v6 0/4] Raspberry Pi 4 DMA addressing support Catalin Marinas

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