From: clemens@ladisch•de (Clemens Ladisch)
To: linux-arm-kernel@lists•infradead.org
Subject: About dma_sync_single_for_{cpu,device}
Date: Tue, 31 Jul 2012 09:34:01 +0200 [thread overview]
Message-ID: <50178A69.8050906@ladisch.de> (raw)
In-Reply-To: <CACYmx9O_TJoSmhiai_Mv09JE3HZ+-V=w8KobTn3zPXtkWbojkw@mail.gmail.com>
Karl Beldan wrote:
> On 7/31/12, Clemens Ladisch <clemens@ladisch•de> wrote:
>> Karl Beldan wrote:
>>> To tx a chunk of data from the SoC => network device, we :
>>> - prepare a buffer with a leading header embedding a pattern,
>>> - trigger the xfer and wait for an irq
>>> // The device updates the pattern and then triggers an irq
>>> - upon irq we check the pattern for the xfer completion
>>>
>>> I was expecting the following to work:
>>> addr = dma_map_single(dev, buffer, size, DMA_TO_DEVICE);
>>
>> Of both the CPU and the device write to the buffer, you must use
>> DMA_BIDIRECTIONAL.
>
> This does not work (tested) : seems to me BIDIRECTIONAL would just
> add invalidate, and invalidate before the ram has been updated, as
> stated, does not work.
Please show the exact sequence of dma_* calls, and also show when and
how the CPU and the device access the buffer.
Regards,
Clemens
next prev parent reply other threads:[~2012-07-31 7:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120730202401.GA4947@gobelin>
2012-07-31 6:45 ` About dma_sync_single_for_{cpu,device} Karl Beldan
2012-07-31 6:59 ` Clemens Ladisch
2012-07-31 7:27 ` Karl Beldan
2012-07-31 7:34 ` Clemens Ladisch [this message]
2012-07-31 8:30 ` Karl Beldan
2012-07-31 9:09 ` Russell King - ARM Linux
2012-07-31 19:31 ` Karl Beldan
2012-07-31 20:08 ` Russell King - ARM Linux
2012-08-01 6:50 ` Karl Beldan
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