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From: Christoph Hellwig <hch@infradead.org>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux@armlinux.org.uk, sza@esh.hu,
	arnd@arndb.de, gregkh@linuxfoundation.org,
	akpm@linux-foundation.org, alexandre.torgue@st.com,
	robin.murphy@arm.com, benjamin.gaignard@linaro.org,
	kbuild-all@01.org, Michal Nazarewicz <mina86@mina86.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool
Date: Tue, 20 Jun 2017 06:49:32 -0700	[thread overview]
Message-ID: <20170620134932.GB31496@infradead.org> (raw)
In-Reply-To: <1495621472-9323-5-git-send-email-vladimir.murzin@arm.com>

On Wed, May 24, 2017 at 11:24:29AM +0100, Vladimir Murzin wrote:
> This patch introduces default coherent DMA pool similar to default CMA
> area concept. To keep other users safe code kept under CONFIG_ARM.

I don't see a CONFIG_ARM in the code, although parts of it are added
under CONFIG_OF_RESERVED_MEM.

But overall this code look a bit odd to me.  As far as I can tell
the dma-coherent.c code is for the case where we have a special
piece of coherent memory close to a device.

If you're allocating out of the global allocator the memory should
come from the normal dma_ops ->alloc allocator - and also take
the attrs into account (e.g. for DMA_ATTR_NON_CONSISTENT or
DMA_ATTR_NO_KERNEL_MAPPING requests you don't need coherent memory)

WARNING: multiple messages have this Message-ID (diff)
From: hch@infradead.org (Christoph Hellwig)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool
Date: Tue, 20 Jun 2017 06:49:32 -0700	[thread overview]
Message-ID: <20170620134932.GB31496@infradead.org> (raw)
In-Reply-To: <1495621472-9323-5-git-send-email-vladimir.murzin@arm.com>

On Wed, May 24, 2017 at 11:24:29AM +0100, Vladimir Murzin wrote:
> This patch introduces default coherent DMA pool similar to default CMA
> area concept. To keep other users safe code kept under CONFIG_ARM.

I don't see a CONFIG_ARM in the code, although parts of it are added
under CONFIG_OF_RESERVED_MEM.

But overall this code look a bit odd to me.  As far as I can tell
the dma-coherent.c code is for the case where we have a special
piece of coherent memory close to a device.

If you're allocating out of the global allocator the memory should
come from the normal dma_ops ->alloc allocator - and also take
the attrs into account (e.g. for DMA_ATTR_NON_CONSISTENT or
DMA_ATTR_NO_KERNEL_MAPPING requests you don't need coherent memory)

  reply	other threads:[~2017-06-20 13:49 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-24 10:24 [PATCH v5 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU Vladimir Murzin
2017-05-24 10:24 ` Vladimir Murzin
2017-05-24 10:24 ` [PATCH v5 1/7] dma: Take into account dma_pfn_offset Vladimir Murzin
2017-05-24 10:24   ` Vladimir Murzin
2017-06-20 13:24   ` Christoph Hellwig
2017-06-20 13:24     ` Christoph Hellwig
2017-06-22 12:47     ` Vladimir Murzin
2017-06-22 12:47       ` Vladimir Murzin
2017-05-24 10:24 ` [PATCH v5 2/7] dma: Add simple dma_noop_mmap Vladimir Murzin
2017-05-24 10:24   ` Vladimir Murzin
2017-06-20 13:23   ` Christoph Hellwig
2017-06-20 13:23     ` Christoph Hellwig
2017-06-22 12:46     ` Vladimir Murzin
2017-06-22 12:46       ` Vladimir Murzin
2017-06-26  9:45       ` Christoph Hellwig
2017-06-26  9:45         ` Christoph Hellwig
2017-05-24 10:24 ` [PATCH v5 3/7] drivers: dma-coherent: Account dma_pfn_offset when used with device tree Vladimir Murzin
2017-05-24 10:24   ` Vladimir Murzin
2017-06-20 13:42   ` Christoph Hellwig
2017-06-20 13:42     ` Christoph Hellwig
2017-06-20 13:50     ` Robin Murphy
2017-06-20 13:50       ` Robin Murphy
2017-06-26  9:37       ` Christoph Hellwig
2017-06-26  9:37         ` Christoph Hellwig
2017-06-22 12:59     ` Vladimir Murzin
2017-06-22 12:59       ` Vladimir Murzin
2017-05-24 10:24 ` [PATCH v5 4/7] drivers: dma-coherent: Introduce default DMA pool Vladimir Murzin
2017-05-24 10:24   ` Vladimir Murzin
2017-06-20 13:49   ` Christoph Hellwig [this message]
2017-06-20 13:49     ` Christoph Hellwig
2017-06-20 14:24     ` Robin Murphy
2017-06-20 14:24       ` Robin Murphy
2017-06-26  9:42       ` Christoph Hellwig
2017-06-26  9:42         ` Christoph Hellwig
2017-06-26 14:08         ` Vladimir Murzin
2017-06-26 14:08           ` Vladimir Murzin
2017-06-27 14:36         ` Robin Murphy
2017-06-27 14:36           ` Robin Murphy
2017-06-27 15:22           ` Christoph Hellwig
2017-06-27 15:22             ` Christoph Hellwig
2017-06-22 13:18     ` Vladimir Murzin
2017-06-22 13:18       ` Vladimir Murzin
2017-06-26  9:44       ` Christoph Hellwig
2017-06-26  9:44         ` Christoph Hellwig
2017-05-24 10:24 ` [PATCH v5 5/7] ARM: NOMMU: Introduce dma operations for noMMU Vladimir Murzin
2017-05-24 10:24   ` Vladimir Murzin
2017-05-24 10:24 ` [PATCH v5 6/7] ARM: NOMMU: Set ARM_DMA_MEM_BUFFERABLE for M-class cpus Vladimir Murzin
2017-05-24 10:24   ` Vladimir Murzin
2017-05-24 10:24 ` [PATCH v5 7/7] ARM: dma-mapping: Remove traces of NOMMU code Vladimir Murzin
2017-05-24 10:24   ` Vladimir Murzin
2017-06-08  8:28 ` [PATCH v5 0/7] ARM: Fix dma_alloc_coherent() and friends for NOMMU Vladimir Murzin
2017-06-08  8:28   ` Vladimir Murzin
2017-06-08 16:25   ` Russell King - ARM Linux
2017-06-08 16:25     ` Russell King - ARM Linux
2017-06-15  7:25     ` Vladimir Murzin
2017-06-15  7:25       ` Vladimir Murzin
2017-06-20 12:59       ` Vladimir Murzin
2017-06-20 12:59         ` Vladimir Murzin
2017-06-20 13:00         ` Christoph Hellwig
2017-06-20 13:00           ` Christoph Hellwig

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