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From: tstdenis@elliptictech.com (Tom St Denis)
To: linux-arm-kernel@lists.infradead.org
Subject: ARM DMA Zones (coherent memory pool)
Date: Tue, 22 Jan 2013 07:36:13 -0500 (EST)	[thread overview]
Message-ID: <644316582.100321.1358858173237.JavaMail.root@elliptictech.com> (raw)
In-Reply-To: <1706190290.100315.1358858042869.JavaMail.root@elliptictech.com>

Hi all,

I was wondering if there was a proper way of instructing the init code (atomic_pool_init) for the DMA coherent subsystem to point to a fixed location instead of using alloc_pages()?

I ask because on our system (Zynq702/706 boards) DDR has a high latency (~25-30 cycles) whereas FPGA memory can be much quicker.  What I'd like to do is create a 256Kbyte memory in FPGA BRAMs and then have the CPU point at it for the DMA zone.

Is that at all possible through a simple kernel cmdline or patch?

Tom

WARNING: multiple messages have this Message-ID (diff)
From: Tom St Denis <tstdenis@elliptictech.com>
To: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Subject: ARM DMA Zones (coherent memory pool)
Date: Tue, 22 Jan 2013 07:36:13 -0500 (EST)	[thread overview]
Message-ID: <644316582.100321.1358858173237.JavaMail.root@elliptictech.com> (raw)
In-Reply-To: <1706190290.100315.1358858042869.JavaMail.root@elliptictech.com>

Hi all,

I was wondering if there was a proper way of instructing the init code (atomic_pool_init) for the DMA coherent subsystem to point to a fixed location instead of using alloc_pages()?

I ask because on our system (Zynq702/706 boards) DDR has a high latency (~25-30 cycles) whereas FPGA memory can be much quicker.  What I'd like to do is create a 256Kbyte memory in FPGA BRAMs and then have the CPU point at it for the DMA zone.

Is that at all possible through a simple kernel cmdline or patch?

Tom

       reply	other threads:[~2013-01-22 12:36 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1706190290.100315.1358858042869.JavaMail.root@elliptictech.com>
2013-01-22 12:36 ` Tom St Denis [this message]
2013-01-22 12:36   ` ARM DMA Zones (coherent memory pool) Tom St Denis

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