Messages in this thread | | | Date | Thu, 13 Dec 2007 21:32:21 -0600 | From | Olof Johansson <> | Subject | Re: [PATCH v2] dmaengine: Simple DMA memcpy test client |
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On Fri, Nov 23, 2007 at 04:34:36PM +0100, Haavard Skinnemoen wrote: > This client tests DMA memcpy using various lengths and various offsets > into the source and destination buffers. It will initialize both > buffers with a know pattern and verify that the DMA engine copies the > requested region and nothing more. > > Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Hi,
First of all: Thanks for sharing this, it's quite useful! I've been playing around with this a bit today, and I've been seeing some odd behaviour.
It seems that once a channel is allocated to dmatest, it will never be freed, i.e. the drivers device_free_chan_resources will never be called on it. Looking at the dma stack, I'm not sure just where it's expected to happen. Once the channel is allocated, the dma_chan_get/put calls all just modify the per-cpu variables, and nothing will ever boil down to a call to kref_put() of the refcount until the _driver_ is deregistered. Not even deregistering the client seems to do it.
Or am I missing something here? Shannon? Dan?
I happened to catch it due to a BUG_ON() in my device_alloc_chan_resources that checked to make sure it wasn't allocated twice without a free inbetween. It hit on the second load of the dmatest module, since they were never freed on unload.
-Olof
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