linux-kernel - Re: [PATCHv5] DMAEngine: Define interleaved transfer request api

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Date:	Fri, 14 Oct 2011 17:21:07 +0530
From:	Jassi Brar <jaswinder.singh@...aro.org>
To:	Barry Song <21cnbao@...il.com>
Cc:	linux-kernel@...r.kernel.org, dan.j.williams@...el.com,
	vkoul@...radead.org, rmk@....linux.org.uk,
	DL-SHA-WorkGroupLinux <workgroup.linux@....com>
Subject: Re: [PATCHv5] DMAEngine: Define interleaved transfer request api

On 14 October 2011 13:02, Barry Song <21cnbao@...il.com> wrote:
>> diff --git a/Documentation/dmaengine.txt b/Documentation/dmaengine.txt
>> index 94b7e0f..962a2d3 100644
>> --- a/Documentation/dmaengine.txt
>> +++ b/Documentation/dmaengine.txt
>> @@ -75,6 +75,10 @@ The slave DMA usage consists of following steps:
>>    slave_sg    - DMA a list of scatter gather buffers from/to a peripheral
>>    dma_cyclic  - Perform a cyclic DMA operation from/to a peripheral till the
>>                  operation is explicitly stopped.
>> +   interleaved_dma - This is common to Slave as well as M2M clients. For slave
>> +                address of devices' fifo could be already known to the driver.
>> +                Various types of operations could be expressed by setting
>> +                appropriate values to the 'dmaxfer_template' members.
>>
>>    A non-NULL return of this transfer API represents a "descriptor" for
>>    the given transaction.
>> @@ -89,6 +93,10 @@ The slave DMA usage consists of following steps:
>>                struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
>>                size_t period_len, enum dma_data_direction direction);
>>
>> +       struct dma_async_tx_descriptor *(*device_prep_interleaved_dma)(
>> +               struct dma_chan *chan, struct dmaxfer_template *xt,
>> +               unsigned long flags);
>> +
>
> what if i want a cyclic interleaved transfer? i think the cyclic
> interleaved transfer is what i want for audio dma.
>
... we need to restore 'bool frm_irq' and add new 'bool cyclic' that
would replay the transfer(i.e, reset dma-pointers to src_start & dst_start)
after 'numf' frames have been transferred.
--
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