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From: Vinod Koul <vinod.koul@intel.com>
To: Baolin Wang <baolin.wang@linaro.org>
Cc: Dan Williams <dan.j.williams@intel.com>,
	Eric Long <eric.long@spreadtrum.com>,
	Mark Brown <broonie@kernel.org>,
	dmaengine@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/5] dmaengine: sprd: Add Spreadtrum DMA configuration
Date: Fri, 13 Apr 2018 15:41:41 +0530	[thread overview]
Message-ID: <20180413101140.GN6014@localhost> (raw)
In-Reply-To: <CAMz4ku+dLk2Gi_20ATW5o-MPvpy-2iF_YJCwyStaH8xPNXSE7Q@mail.gmail.com>

On Fri, Apr 13, 2018 at 02:41:48PM +0800, Baolin Wang wrote:
> On 13 April 2018 at 14:36, Vinod Koul <vinod.koul@intel.com> wrote:
> > On Fri, Apr 13, 2018 at 02:17:34PM +0800, Baolin Wang wrote:
> >
> >> > Agreed, users only care about grabbing a channel, setting a descriptor and
> >> > submitting that.
> >> >
> >> > I think you need to go back and think about this a bit, please do go thru
> >> > dmaengine documentation and see other driver examples.
> >> >
> >> > We don't typically expose these to users, they give us a transfer and we set
> >> > that up in hardware for efficient. Its DMA so people expect us to use fastest
> >> > mechanism available.
> >>
> >> But there are some configuration are really special for Spreadtrum
> >> DMA, and must need user to specify how to configure, especially some
> >> scenarios of audio. So I wander if we can add one pointer for
> >> 'dma_slave_config' to expand some special DMA configuration
> >> requirements, like:
> >>
> >> struct dma_slave_config {
> >>     ......
> >>     unsigned int slave_id;
> >>     void *platform_data;
> >> };
> >>
> >> So if some DMA has some special configuration (such as Spreadtrum
> >> DMA), they can user this platform_data pointer. Like xilinx DMA, they
> >> also have some special configuration.
> >
> > Well we all think our HW is special and needs some additional stuff, most of
> > the cases turns out not to be the case.
> >
> > Can you explain how audio in this case additional configuration...
> >
> 
> Beside the general configuration, our audio driver will configure the
> fragment length, block length, maybe transaction length, and they must
> specify the request type and interrupt type, these are what we want to
> export for users.

First doesn't it use sound dmaengine library, it should :)

Second, I think you should calculate the lengths based on given input. Audio
is circular buffer so you shall create a circular linked list and submit.
See how other driver implement circular prepare callback

-- 
~Vinod

  reply	other threads:[~2018-04-13 10:07 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-10  7:46 [PATCH 1/5] dmaengine: sprd: Define the DMA transfer step type Baolin Wang
2018-04-10  7:46 ` [PATCH 2/5] dmaengine: sprd: Define the DMA data width type Baolin Wang
2018-04-10  7:46 ` [PATCH 3/5] dmaengine: sprd: Move DMA request mode and interrupt type into head file Baolin Wang
2018-04-10  7:46 ` [PATCH 4/5] dmaengine: sprd: Add Spreadtrum DMA configuration Baolin Wang
2018-04-11  9:36   ` Vinod Koul
2018-04-11 12:13     ` Baolin Wang
2018-04-12  9:37       ` Vinod Koul
2018-04-12 11:30         ` Baolin Wang
2018-04-12 11:36           ` Baolin Wang
2018-04-13  3:43             ` Vinod Koul
2018-04-13  6:17               ` Baolin Wang
2018-04-13  6:36                 ` Vinod Koul
2018-04-13  6:41                   ` Baolin Wang
2018-04-13 10:11                     ` Vinod Koul [this message]
2018-04-13 10:48                       ` Baolin Wang
2018-04-16  3:58                     ` Vinod Koul
2018-04-16  6:32                       ` Baolin Wang
2018-04-16 15:35                         ` Vinod Koul
2018-04-17  6:06                           ` Baolin Wang
2018-04-13  3:39           ` Vinod Koul
2018-04-13  5:44             ` Baolin Wang
2018-04-10  7:46 ` [PATCH 5/5] dmaengine: sprd: Add 'device_config' and 'device_prep_slave_sg' interfaces Baolin Wang
2018-04-11  9:40   ` Vinod Koul
2018-04-11 10:51     ` Baolin Wang
2018-04-17 10:45   ` Lars-Peter Clausen
2018-04-18  5:40     ` Baolin Wang
2018-04-11  9:24 ` [PATCH 1/5] dmaengine: sprd: Define the DMA transfer step type Vinod Koul
2018-04-11 10:49   ` Baolin Wang

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