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

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Date:   Mon, 31 Jul 2017 18:04:05 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Abhishek Sahu <absahu@...eaurora.org>
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 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

> 
> >>>  */
> >>> 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

-- 
~Vinod