Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 10 Feb 2020 16:23:29 +0100
Message-ID: <s5ha75qfoum.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc:     <broonie@kernel.org>, <lgirdwood@gmail.com>, <tiwai@suse.com>,
        <perex@perex.cz>, <lars@metafoo.de>, <alsa-devel@alsa-project.org>,
        <vkoul@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] ALSA: dmaengine_pcm: Consider DMA cache caused delay in pointer callback
In-Reply-To: <20200210151402.29634-1-peter.ujfalusi@ti.com>
References: <20200210151402.29634-1-peter.ujfalusi@ti.com>
User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka)
 FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3
 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO)
MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka")
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, 10 Feb 2020 16:14:02 +0100,
Peter Ujfalusi wrote:
> 
> Some DMA engines can have big FIFOs which adds to the latency.
> The DMAengine framework can report the FIFO utilization in bytes. Use this
> information for the delay reporting.
> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
> ---
> Hi,
> 
> Changes since v1:
> - use bytes_to_frames() for the DMA delay calculation
> - Drop changes to soc-pcm
> 
> 5.6-rc1 now have support for reporting the DMA cached data.
> With this patch we can include it to the delay calculation.
> The first DMA driver which reports this is the TI K3 UDMA driver.
> 
> Regards,
> Peter
> 
>  sound/core/pcm_dmaengine.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c
> index 5749a8a49784..d8be7b488162 100644
> --- a/sound/core/pcm_dmaengine.c
> +++ b/sound/core/pcm_dmaengine.c
> @@ -247,9 +247,14 @@ snd_pcm_uframes_t snd_dmaengine_pcm_pointer(struct snd_pcm_substream *substream)
>  
>  	status = dmaengine_tx_status(prtd->dma_chan, prtd->cookie, &state);
>  	if (status == DMA_IN_PROGRESS || status == DMA_PAUSED) {
> +		struct snd_pcm_runtime *runtime = substream->runtime;
> +
>  		buf_size = snd_pcm_lib_buffer_bytes(substream);
>  		if (state.residue > 0 && state.residue <= buf_size)
>  			pos = buf_size - state.residue;
> +
> +		runtime->delay = bytes_to_frames(runtime,
> +						 state.in_flight_bytes);

Another call of bytes_to_frames() below...

>  	}
>  
>  	return bytes_to_frames(substream->runtime, pos);

... refers to substream->runtime.
Better to align both places, either runtime or substream->runtime.

With that minor nitpick, the change looks good:
Reviewed-by: Takashi Iwai <tiwai@suse.de>


thanks,

Takashi