dmaengine Archive on lore.kernel.org
 help / color / Atom feed
From: Vinod Koul <vkoul@kernel.org>
To: Sameer Pujar <spujar@nvidia.com>
Cc: dan.j.williams@intel.com, tiwai@suse.com, jonathanh@nvidia.com,
	dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [RFC] dmaengine: add fifo_size member
Date: Thu, 2 May 2019 17:55:06 +0530
Message-ID: <20190502122506.GP3845@vkoul-mobl.Dlink> (raw)
In-Reply-To: <e852d576-9cc2-ed42-1a1a-d696112c88bf@nvidia.com>

On 02-05-19, 16:23, Sameer Pujar wrote:
> 
> On 5/2/2019 11:34 AM, Vinod Koul wrote:
> > On 30-04-19, 17:00, Sameer Pujar wrote:
> > > During the DMA transfers from memory to I/O, it was observed that transfers
> > > were inconsistent and resulted in glitches for audio playback. It happened
> > > because fifo size on DMA did not match with slave channel configuration.
> > > 
> > > currently 'dma_slave_config' structure does not have a field for fifo size.
> > > Hence the platform pcm driver cannot pass the fifo size as a slave_config.
> > > Note that 'snd_dmaengine_dai_dma_data' structure has fifo_size field which
> > > cannot be used to pass the size info. This patch introduces fifo_size field
> > > and the same can be populated on slave side. Users can set required size
> > > for slave peripheral (multiple channels can be independently running with
> > > different fifo sizes) and the corresponding sizes are programmed through
> > > dma_slave_config on DMA side.
> > FIFO size is a hardware property not sure why you would want an
> > interface to program that?
> > 
> > On mismatch, I guess you need to take care of src/dst_maxburst..
> Yes, FIFO size is a HW property. But it is SW configurable(atleast in my
> case) on
> slave side and can be set to different sizes. The src/dst_maxburst is

Are you sure, have you talked to HW folks on that? IIUC you are
programming the data to be used in FIFO not the FIFO length!

> programmed
> for specific values, I think this depends on few factors related to
> bandwidth
> needs of client, DMA needs of the system etc.,

Precisely

> In such cases how does DMA know the actual FIFO depth of slave peripheral?

Why should DMA know? Its job is to push/pull data as configured by
peripheral driver. The peripheral driver knows and configures DMA
accordingly.

 
> > > Request for feedback/suggestions.
> > > 
> > > Signed-off-by: Sameer Pujar <spujar@nvidia.com>
> > > ---
> > >   include/linux/dmaengine.h | 3 +++
> > >   1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> > > index d49ec5c..9ec198b 100644
> > > --- a/include/linux/dmaengine.h
> > > +++ b/include/linux/dmaengine.h
> > > @@ -351,6 +351,8 @@ enum dma_slave_buswidth {
> > >    * @slave_id: Slave requester id. Only valid for slave channels. The dma
> > >    * slave peripheral will have unique id as dma requester which need to be
> > >    * pass as slave config.
> > > + * @fifo_size: Fifo size value. The dma slave peripheral can configure required
> > > + * fifo size and the same needs to be passed as slave config.
> > >    *
> > >    * This struct is passed in as configuration data to a DMA engine
> > >    * in order to set up a certain channel for DMA transport at runtime.
> > > @@ -376,6 +378,7 @@ struct dma_slave_config {
> > >   	u32 dst_port_window_size;
> > >   	bool device_fc;
> > >   	unsigned int slave_id;
> > > +	u32 fifo_size;
> > >   };
> > >   /**
> > > -- 
> > > 2.7.4

-- 
~Vinod

  reply index

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-30 11:30 Sameer Pujar
2019-04-30 11:30 ` [PATCH] " Sameer Pujar
2019-05-02  6:04 ` Vinod Koul
2019-05-02  6:04   ` [PATCH] " Vinod Koul
2019-05-02 10:53   ` Sameer Pujar
2019-05-02 12:25     ` Vinod Koul [this message]
2019-05-02 13:29       ` Sameer Pujar
2019-05-03 19:10         ` Peter Ujfalusi
2019-05-04 10:23         ` Vinod Koul
2019-05-06 13:04           ` Sameer Pujar
2019-05-06 15:50             ` Vinod Koul
2019-06-06  3:49               ` Sameer Pujar
2019-06-06  6:00                 ` Peter Ujfalusi
2019-06-06  6:41                   ` Sameer Pujar
2019-06-06  7:14                     ` Jon Hunter
2019-06-06 10:22                       ` Peter Ujfalusi
2019-06-06 10:49                         ` Jon Hunter
2019-06-06 11:54                           ` Peter Ujfalusi
2019-06-06 12:37                             ` Jon Hunter
2019-06-06 13:45                               ` Dmitry Osipenko
2019-06-06 13:55                                 ` Dmitry Osipenko
2019-06-06 14:26                                   ` Jon Hunter
2019-06-06 14:36                                     ` Jon Hunter
2019-06-06 14:36                                     ` Dmitry Osipenko
2019-06-06 14:47                                       ` Jon Hunter
2019-06-06 14:25                                 ` Jon Hunter
2019-06-06 15:18                                   ` Dmitry Osipenko
2019-06-06 16:32                                     ` Jon Hunter
2019-06-06 16:44                                       ` Dmitry Osipenko
2019-06-06 16:53                                         ` Jon Hunter
2019-06-06 17:25                                           ` Dmitry Osipenko
2019-06-06 17:56                                             ` Dmitry Osipenko
2019-06-07  9:24                                             ` Jon Hunter
2019-06-07  5:50                               ` Peter Ujfalusi
2019-06-07  9:18                                 ` Jon Hunter
2019-06-07 10:27                                   ` Jon Hunter
2019-06-07 12:17                                     ` Peter Ujfalusi
2019-06-07 12:58                                       ` Jon Hunter
2019-06-07 13:35                                         ` Peter Ujfalusi
2019-06-07 20:53                                           ` Dmitry Osipenko
2019-06-10  8:01                                             ` Jon Hunter
2019-06-10  7:59                                           ` Jon Hunter
2019-06-13  4:43                 ` Vinod Koul
2019-06-17  7:07                   ` Sameer Pujar
2019-06-18  4:33                     ` Vinod Koul
2019-06-20 10:29                       ` Sameer Pujar
2019-06-24  6:26                         ` Vinod Koul
2019-06-25  2:57                           ` Sameer Pujar
2019-07-05  6:15                             ` Sameer Pujar
2019-07-15 15:42                               ` Sameer Pujar
2019-07-19  5:04                               ` Vinod Koul
2019-07-23  5:54                                 ` Sameer Pujar
2019-07-29  6:10                                   ` Vinod Koul
2019-07-31  9:48                                     ` Jon Hunter
2019-07-31 15:16                                       ` Vinod Koul
2019-08-02  8:51                                         ` Jon Hunter
2019-08-08 12:38                                           ` Vinod Koul
2019-08-19 15:56                                             ` Jon Hunter
2019-08-20 11:05                                               ` Vinod Koul
2019-09-16  9:02                                                 ` Sameer Pujar

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190502122506.GP3845@vkoul-mobl.Dlink \
    --to=vkoul@kernel.org \
    --cc=dan.j.williams@intel.com \
    --cc=dmaengine@vger.kernel.org \
    --cc=jonathanh@nvidia.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=spujar@nvidia.com \
    --cc=tiwai@suse.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

dmaengine Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/dmaengine/0 dmaengine/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dmaengine dmaengine/ https://lore.kernel.org/dmaengine \
		dmaengine@vger.kernel.org
	public-inbox-index dmaengine

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.dmaengine


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git