linux-kernel - Re: [PATCH v2 1/3] dmaengine: add DMA_PREP

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Date:   Fri, 28 Jul 2017 21:38:56 +0530
From:   Abhishek Sahu <absahu@...eaurora.org>
To:     Vinod Koul <vinod.koul@...el.com>
Cc:     andy.gross@...aro.org, david.brown@...aro.org,
        dan.j.williams@...el.com, linux-arm-msm@...r.kernel.org,
        linux-soc@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] dmaengine: add DMA_PREP_CMD for non-Data
 descriptors.

On 2017-07-19 17:48, Abhishek Sahu wrote:
> On 2017-07-19 15:37, Vinod Koul wrote:
>> On Mon, Jun 26, 2017 at 06:19:27PM +0530, Abhishek Sahu wrote:
>>> Some of the DMA controllers are capable of issuing the commands
>>> to peripheral by the DMA. These commands can be list of register
>>> reads/writes and its different from normal data reads/writes.
>>> This patch adds new flag DMA_PREP_CMD in DMA API which tells
>>> the driver that the data passed to DMA API is in command format
>>> and DMA driver will form descriptor in the required format.
>>> 
>>> This flag can be used by any DMA controller driver which requires
>>> special handling for non-Data descriptors.
>> 
>> Please add Documentation for this new flag in
>> Documentation/dmaengine/provider.txt
>> 
> 
>  Sure. I will add update the documentation in v3.
> 
>>> 
>>> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
>>> ---
>>>  include/linux/dmaengine.h | 3 +++
>>>  1 file changed, 3 insertions(+)
>>> 
>>> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
>>> index 5336808..bbc297e 100644
>>> --- a/include/linux/dmaengine.h
>>> +++ b/include/linux/dmaengine.h
>>> @@ -186,6 +186,8 @@ struct dma_interleaved_template {
>>>   *  on the result of this operation
>>>   * @DMA_CTRL_REUSE: client can reuse the descriptor and submit again 
>>> till
>>>   *  cleared or freed
>>> + * @DMA_PREP_CMD: tell the driver that the data passed to DMA API is 
>>> in command
>>> + *  format and it will be used for configuring the peripheral 
>>> registers.
>> 
>> Can you explain what is command format..?
>> 
> 
>  The command format is not generic and its format will be dependent
>  upon DMA engine. The client drivers will give data in its own
>  command formats and this flag will be passed to DMA API’s to do
>  the parsing according to its own command format.
> 
>  Currently this flag description and name is inclined towards
>  Qualcomm BAM DMA command flag. We want to make this flag as
>  generic one so require your suggestion regarding this.
>  Will renaming this flag as DMA_PREP_NON_DATA or
>  DMA_PREP_CUSTOM make it more generic?
> 

  can we use same flag name DMA_PREP_CMD or should we
  go for some other name?

>>>   */
>>>  enum dma_ctrl_flags {
>>>  	DMA_PREP_INTERRUPT = (1 << 0),
>>> @@ -195,6 +197,7 @@ enum dma_ctrl_flags {
>>>  	DMA_PREP_CONTINUE = (1 << 4),
>>>  	DMA_PREP_FENCE = (1 << 5),
>>>  	DMA_CTRL_REUSE = (1 << 6),
>>> +	DMA_PREP_CMD = (1 << 7),
>>>  };
>>> 


-- 
Abhishek Sahu