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From: Vinod Koul <vkoul@kernel.org>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>,
	dmaengine@vger.kernel.org, Michal Simek <michal.simek@xilinx.com>,
	Hyun Kwon <hyun.kwon@xilinx.com>,
	Tejas Upadhyay <tejasu@xilinx.com>,
	Satish Kumar Nagireddy <SATISHNA@xilinx.com>
Subject: Re: [PATCH v3 2/6] dmaengine: Add interleaved cyclic transaction type
Date: Tue, 3 Mar 2020 10:02:54 +0530
Message-ID: <20200303043254.GN4148@vkoul-mobl> (raw)
In-Reply-To: <20200302073728.GB9177@pendragon.ideasonboard.com>

Hi Laurent,

On 02-03-20, 09:37, Laurent Pinchart wrote:

> > I would be more comfortable in calling an API to do so :)
> > The flow I am thinking is:
> > 
> > - prep cyclic1 txn
> > - submit cyclic1 txn
> > - call issue_pending() (cyclic one starts)
> > 
> > - prep cyclic2 txn
> > - submit cyclic2 txn
> > - signal_cyclic1_txn aka terminate_cookie()
> > - cyclic1 completes, switch to cyclic2 (dmaengine driver)
> > - get callback for cyclic1 (optional)
> > 
> > To check if hw supports terminate_cookie() or not we can check if the
> > callback support is implemented
> 
> Two questions though:
> 
> - Where is .issue_pending() called for cyclic2 in your above sequence ?
>   Surely it should be called somewhere, as the DMA engine API requires
>   .issue_pending() to be called for a transfer to be executed, otherwise
>   it stays in the submitted but not pending queue.

Sorry missed that one, I would do that after submit cyclic2 txn step and
then signal signal_cyclic1_txn termination

> - With the introduction of a new .terminate_cookie() operation, we need
>   to specify that operation for all transfer types. What's its

Correct

>   envisioned semantics for non-cyclic transfers ? And how do DMA engine
>   drivers report that they support .terminate_cookie() for cyclic
>   transfers but not for other transfer types (the counterpart of
>   reporting, in my proposition, that .issue_pending() isn't supported
>   replace the current cyclic transfer) ?

Typically for dmaengine controller cyclic is *not* a special mode, only
change is that a list provided to controller is circular.

So, the .terminate_cookie() should be a feature for all type of txn's.
If for some reason (dont discount what hw designers can do) a controller
supports this for some specific type(s), then they should return
-ENOTSUPP for cookies that do not support and let the caller know.

-- 
~Vinod

  reply index

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-23  2:29 [PATCH v3 0/6] dma: Add Xilinx ZynqMP DPDMA driver Laurent Pinchart
2020-01-23  2:29 ` [PATCH v3 1/6] dt: bindings: dma: xilinx: dpdma: DT bindings for Xilinx DPDMA Laurent Pinchart
2020-01-23  2:29 ` [PATCH v3 2/6] dmaengine: Add interleaved cyclic transaction type Laurent Pinchart
2020-01-23  8:03   ` Peter Ujfalusi
2020-01-23  8:43     ` Vinod Koul
2020-01-23  8:51       ` Peter Ujfalusi
2020-01-23 12:23         ` Laurent Pinchart
2020-01-24  6:10           ` Vinod Koul
2020-01-24  8:50             ` Laurent Pinchart
2020-02-10 14:06               ` Laurent Pinchart
2020-02-13 13:29                 ` Vinod Koul
2020-02-13 13:48                   ` Laurent Pinchart
2020-02-13 14:07                     ` Vinod Koul
2020-02-13 14:15                       ` Peter Ujfalusi
2020-02-13 16:52                         ` Laurent Pinchart
2020-02-14  4:23                           ` Vinod Koul
2020-02-14 16:22                             ` Laurent Pinchart
2020-02-17 10:00                               ` Peter Ujfalusi
2020-02-19  9:25                                 ` Vinod Koul
2020-02-26 16:30                                   ` Laurent Pinchart
2020-03-02  3:47                                     ` Vinod Koul
2020-03-02  7:37                                       ` Laurent Pinchart
2020-03-03  4:32                                         ` Vinod Koul [this message]
2020-03-03 19:22                                           ` Laurent Pinchart
2020-03-04  5:13                                             ` Vinod Koul
2020-03-04  8:01                                               ` Laurent Pinchart
2020-03-04 15:37                                                 ` Vinod Koul
2020-03-04 16:00                                                   ` Laurent Pinchart
2020-03-04 16:24                                                     ` Vinod Koul
     [not found]                                                       ` <20200311155248.GA4772@pendragon.ideasonboard.com>
2020-03-18 15:14                                                         ` Laurent Pinchart
2020-03-25 16:00                                                           ` Laurent Pinchart
2020-03-26  7:02                                                         ` Vinod Koul
2020-04-08 17:00                                                           ` Laurent Pinchart
2020-04-15 15:12                                                             ` Laurent Pinchart
2020-03-06 14:49                                                     ` Peter Ujfalusi
2020-03-11 23:15                                                       ` Laurent Pinchart
2020-02-26 16:24                                 ` Laurent Pinchart
2020-03-02  3:42                                   ` Vinod Koul
2020-01-24  7:20           ` Peter Ujfalusi
2020-01-24  7:38             ` Peter Ujfalusi
2020-01-24  8:58               ` Laurent Pinchart
2020-01-24  8:56             ` Laurent Pinchart
2020-01-23  2:29 ` [PATCH v3 3/6] dmaengine: virt-dma: Use lockdep to check locking requirements Laurent Pinchart
2020-01-23  2:29 ` [PATCH v3 4/6] dmaengine: xilinx: dpdma: Add the Xilinx DisplayPort DMA engine driver Laurent Pinchart
2020-01-23  2:29 ` [PATCH v3 5/6] dmaengine: xilinx: dpdma: Add debugfs support Laurent Pinchart
2020-01-23  2:29 ` [PATCH v3 6/6] arm64: dts: zynqmp: Add DPDMA node Laurent Pinchart

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