From: Marc Pignat <marc.pignat@hevs.ch>
To: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Andrew Victor <linux@maxim.org.za>,
kernel@avr32linux.org, linux-kernel@vger.kernel.org,
Remy Bohmer <linux@bohmer.net>,
Chip Coldwell <coldwell@redhat.com>
Subject: Re: [PATCH 6/6] atmel_serial: Add DMA support
Date: Wed, 23 Jan 2008 14:18:38 +0100 [thread overview]
Message-ID: <200801231418.38997.marc.pignat@hevs.ch> (raw)
In-Reply-To: <20080123134553.144ca487@dhcp-252-066.norway.atmel.com>
Hi!
On Wednesday 23 January 2008, Haavard Skinnemoen wrote:
> On Wed, 23 Jan 2008 13:30:32 +0100
> Marc Pignat <marc.pignat@hevs.ch> wrote:
> > On Wednesday 23 January 2008, Haavard Skinnemoen wrote:
...
>
> Ok, but then any power of two larger than the cache line size should be
> fine, assuming kmalloc() returns a properly aligned buffer.
Yes. The memory should be allocated using GFP_KERNEL | GFP_DMA flags, but this
is probably a nop on at91 and avr32.
I prepare a patch using the generic dma api (allocation + dma mapping in one
call = simpler code).
>
> Other than that, I can't see any reason why a platform with 64 byte
> cache lines should need larger buffers than one with 32 byte cache
> lines.
If the memory at the end of the cacheline is used by the cpu, it will be
corrupted while you call dma_sync_single_for_cpu(..., DMA_FROM_DEVICE);
...
> There are still issues with the DMA code that the PIO code doesn't
> have. So I think it should be selectable until we can sort out the
> error/break handling.
ok
>
> Haavard
>
Regards
Marc
next prev parent reply other threads:[~2008-01-23 13:18 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-22 14:50 [PATCH v3 0/6] atmel_serial: Cleanups, irq handler splitup & DMA Haavard Skinnemoen
2008-01-22 14:50 ` [PATCH 1/6] atmel_serial: Clean up the code Haavard Skinnemoen
2008-01-22 14:50 ` [PATCH 2/6] atmel_serial: Use cpu_relax() when busy-waiting Haavard Skinnemoen
2008-01-22 14:50 ` [PATCH 3/6] atmel_serial: Use existing console options only if BRG is running Haavard Skinnemoen
2008-01-22 14:50 ` [PATCH 4/6] atmel_serial: Fix bugs in probe() error path and remove() Haavard Skinnemoen
2008-01-22 14:50 ` [PATCH 5/6] atmel_serial: Split the interrupt handler Haavard Skinnemoen
2008-01-22 14:50 ` [PATCH 6/6] atmel_serial: Add DMA support Haavard Skinnemoen
2008-01-22 16:52 ` Marc Pignat
2008-01-23 11:53 ` Haavard Skinnemoen
2008-01-23 12:30 ` Marc Pignat
2008-01-23 12:45 ` Haavard Skinnemoen
2008-01-23 13:18 ` Marc Pignat [this message]
2008-01-23 13:35 ` Haavard Skinnemoen
2008-01-23 13:52 ` Marc Pignat
2008-01-23 14:05 ` Haavard Skinnemoen
2008-01-23 15:04 ` Alan Cox
2008-01-23 15:14 ` Haavard Skinnemoen
2008-01-23 16:41 ` Alan Cox
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