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From: Christoph Hellwig <hch@lst.de>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: Kate Stewart <kstewart@linuxfoundation.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	info@metux.net, linux@armlinux.org.uk,
	linux-stm32@st-md-mailman.stormreply.com,
	Rob Herring <robh+dt@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	tglx@linutronix.de, dillon min <dillon.minfei@gmail.com>,
	Christoph Hellwig <hch@lst.de>,
	allison@lohutok.net
Subject: Re: [PATCH 2/2] arm-nommu: Add use_reserved_mem() to check if device support reserved memory
Date: Tue, 9 Jun 2020 19:34:55 +0200	[thread overview]
Message-ID: <20200609173455.GA25467@lst.de> (raw)
In-Reply-To: <b0c85637-4646-614b-d406-49aa72ce52e1@arm.com>

On Tue, Jun 09, 2020 at 05:25:04PM +0100, Vladimir Murzin wrote:
> Even though commit mentions ARM, I do not see how mmap would continue
> to work for NOMMU with dma-direct. ARM NOMMU needs it's own DMA operations
> only in cases where caches are implemented or active, in other cases it
> fully relies on dma-direct.

> It looks to me that we either should provide NOMMU variant for mmap in
> dma/direct or (carefully) fix dma/mapping.

I think dma-direct is the right place, the common helpers in
dma/mapping.c are basically the red headed stepchilds for misc
IOMMU drivers not covered by dma-iommu only.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: Christoph Hellwig <hch@lst.de>,
	dillon min <dillon.minfei@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	linux@armlinux.org.uk,
	Kate Stewart <kstewart@linuxfoundation.org>,
	allison@lohutok.net, info@metux.net, tglx@linutronix.de,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	linux-stm32@st-md-mailman.stormreply.com,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] arm-nommu: Add use_reserved_mem() to check if device support reserved memory
Date: Tue, 9 Jun 2020 19:34:55 +0200	[thread overview]
Message-ID: <20200609173455.GA25467@lst.de> (raw)
In-Reply-To: <b0c85637-4646-614b-d406-49aa72ce52e1@arm.com>

On Tue, Jun 09, 2020 at 05:25:04PM +0100, Vladimir Murzin wrote:
> Even though commit mentions ARM, I do not see how mmap would continue
> to work for NOMMU with dma-direct. ARM NOMMU needs it's own DMA operations
> only in cases where caches are implemented or active, in other cases it
> fully relies on dma-direct.

> It looks to me that we either should provide NOMMU variant for mmap in
> dma/direct or (carefully) fix dma/mapping.

I think dma-direct is the right place, the common helpers in
dma/mapping.c are basically the red headed stepchilds for misc
IOMMU drivers not covered by dma-iommu only.

  reply	other threads:[~2020-06-09 17:35 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-08  8:30 [PATCH 0/2] Use 'arm_nommu_dma_ops' to handle dma memroy if device offer consistent dma memory region dillon.minfei
2020-06-08  8:30 ` dillon.minfei
2020-06-08  8:30 ` [PATCH 1/2] ARM: dts: stm32: Setup 4M bytes reserved memory for mmap dillon.minfei
2020-06-08  8:30   ` dillon.minfei
2020-06-09 15:58   ` dillon min
2020-06-09 15:58     ` dillon min
2020-06-08  8:30 ` [PATCH 2/2] arm-nommu: Add use_reserved_mem() to check if device support reserved memory dillon.minfei
2020-06-08  8:30   ` dillon.minfei
2020-06-09 14:08   ` Vladimir Murzin
2020-06-09 14:08     ` Vladimir Murzin
2020-06-09 15:22     ` dillon min
2020-06-09 15:22       ` dillon min
2020-06-09 15:36       ` Christoph Hellwig
2020-06-09 15:36         ` Christoph Hellwig
2020-06-09 15:43         ` Vladimir Murzin
2020-06-09 15:43           ` Vladimir Murzin
2020-06-09 16:25           ` Vladimir Murzin
2020-06-09 16:25             ` Vladimir Murzin
2020-06-09 17:34             ` Christoph Hellwig [this message]
2020-06-09 17:34               ` Christoph Hellwig
2020-06-10  2:24               ` dillon min
2020-06-10  2:24                 ` dillon min
2020-06-10  7:24     ` Christoph Hellwig
2020-06-10  7:24       ` Christoph Hellwig
2020-06-10  8:19       ` Vladimir Murzin
2020-06-10  8:19         ` Vladimir Murzin
2020-06-11 15:45         ` Vladimir Murzin
2020-06-11 15:45           ` Vladimir Murzin
2020-06-12  2:15           ` dillon min
2020-06-12  2:15             ` dillon min
2020-06-09 15:58 ` [PATCH 0/2] Use 'arm_nommu_dma_ops' to handle dma memroy if device offer consistent dma memory region dillon min
2020-06-09 15:58   ` dillon min

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