From: Vinod Koul <vinod.koul@intel.com>
To: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: "Geert Uytterhoeven" <geert@linux-m68k.org>,
"Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
"Dan Williams" <dan.j.williams@intel.com>,
"Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>,
dmaengine@vger.kernel.org,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Hiroyuki Yokoyama" <hiroyuki.yokoyama.vx@renesas.com>
Subject: Re: [PATCH v3] dmaengine: rcar-dmac: use TCRB instead of TCR for residue
Date: Fri, 20 Oct 2017 11:45:16 +0530 [thread overview]
Message-ID: <20171020061516.GM30097@localhost> (raw)
In-Reply-To: <87bml4c5e0.wl%kuninori.morimoto.gx@renesas.com>
On Thu, Oct 19, 2017 at 01:15:13AM +0000, Kuninori Morimoto wrote:
> From: Hiroyuki Yokoyama <hiroyuki.yokoyama.vx@renesas.com>
>
> SYS/RT/Audio DMAC includes independent data buffers for reading
> and writing. Therefore, the read transfer counter and write transfer
> counter have different values.
> TCR indicates read counter, and TCRB indicates write counter.
> The relationship is like below.
>
> TCR TCRB
> [SOURCE] -> [DMAC] -> [SINK]
>
> In the MEM_TO_DEV direction, what really matters is how much data has
> been written to the device. If the DMA is interrupted between read and
> write, then, the data doesn't end up in the destination, so shouldn't
> be counted. TCRB is thus the register we should use in this cases.
>
> In the DEV_TO_MEM direction, the situation is more complex. Both the
> read and write side are important. What matters from a data consumer
> point of view is how much data has been written to memory.
> On the other hand, if the transfer is interrupted between read and
> write, we'll end up losing data. It can also be important to report.
>
> In the MEM_TO_MEM direction, what matters is of course how much data
> has been written to memory from data consumer point of view.
> Here, because read and write have independent data buffers, it will
> take a while for TCR and TCRB to become equal. Thus we should check
> TCRB in this case, too.
>
> Thus, all cases we should check TCRB instead of TCR.
>
> Without this patch, Sound Capture has noise after PluseAudio support
> (= 07b7acb51d2 ("ASoC: rsnd: update pointer more accurate")), because
> the recorder will use wrong residue counter which indicates transferred
> from sound device, but in reality the data was not yet put to memory
> and recorder will record it.
Applied, thanks.
--
~Vinod
next prev parent reply other threads:[~2017-10-20 6:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-19 1:15 [PATCH v3] dmaengine: rcar-dmac: use TCRB instead of TCR for residue Kuninori Morimoto
2017-10-19 7:41 ` Geert Uytterhoeven
2017-10-19 11:56 ` Laurent Pinchart
2017-10-20 6:15 ` Vinod Koul [this message]
2017-10-31 10:45 ` Geert Uytterhoeven
2017-10-31 10:46 ` Geert Uytterhoeven
2017-10-31 11:41 ` Vinod Koul
2017-11-01 3:07 ` Kuninori Morimoto
2017-11-06 1:24 ` Kuninori Morimoto
2017-11-06 13:27 ` Geert Uytterhoeven
2017-11-08 5:35 ` Vinod Koul
2017-11-08 6:33 ` Kuninori Morimoto
2017-11-08 8:37 ` Vinod Koul
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