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

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Date:   Mon, 31 Jul 2017 18:31:55 +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 2017-07-31 18:04, Vinod Koul wrote:
> On Fri, Jul 28, 2017 at 09:38:56PM +0530, Abhishek Sahu wrote:
>> 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?
> 
> Are you asking for using DMA_PREP_CMD, for that I think should be ok
> 
> If you asking about adding a new flag with DMA_PREP_CMD, then it would 
> no
> 

  Thanks Vinod.

  We just want to add only one flag with name DMA_PREP_CMD and no
  other new flag.

  I will update the description for DMA_PREP_CMD in
  Documentation/dmaengine/provider.txt

>> 
>> >>>  */
>> >>> 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),
>> >>> };
>> >>>
>>