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From: Maxime Ripard <maxime@cerno.tech>
To: Samuel Holland <samuel@sholland.org>
Cc: Ondrej Jirman <megous@megous.com>,
	alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
	Takashi Iwai <tiwai@suse.com>,
	Liam Girdwood <lgirdwood@gmail.com>, Chen-Yu Tsai <wens@csie.org>,
	Mark Brown <broonie@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 10/17] ASoC: sun8i-codec: Automatically set the system sample rate
Date: Mon, 19 Oct 2020 10:25:47 +0200
Message-ID: <20201019082547.um4tepbittn2cna3@gilmour.lan> (raw)
In-Reply-To: <20201014061941.4306-11-samuel@sholland.org>


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On Wed, Oct 14, 2020 at 01:19:34AM -0500, Samuel Holland wrote:
> The sun8i codec has three clock/sample rate domains:
>  - The AIF1 domain, with a sample rate equal to AIF1 LRCK
>  - The AIF2 domain, with a sample rate equal to AIF2 LRCK
>  - The SYSCLK domain, containing the ADC, DAC, and effects (AGC/DRC),
>    with a sample rate given by a divisor from SYSCLK. The divisor is
>    controlled by the AIF1_FS or AIF2_FS field in SYS_SR_CTRL, depending
>    on if SYSCLK's source is AIF1CLK or AIF2CLK, respectively. The exact
>    sample rate depends on if SYSCLK is running at 22.6 MHz or 24.6 MHz.
> 
> When an AIF (currently only AIF1) is active, the ADC and DAC should run
> at that sample rate to avoid artifacting. Sample rate conversion is only
> available when multiple AIFs are active and are routed to each other;
> this means the sample rate conversion hardware usually cannot be used.
> 
> Only attach the event hook to the channel 0 AIF widgets, since we only
> need one event when a DAI stream starts or stops. Channel 0 is always
> brought up with a DAI stream, regardless of the number of channels in
> the stream.
> 
> The ADC and DAC (along with their effects blocks) can be used even if
> no AIFs are in use. In that case, we should select an appropriate sample
> rate divisor, instead of keeping the last-used AIF sample rate.
> 44.1/48 kHz was chosen to balance audio quality and power consumption.
> 
> Since the sample rate is tied to active AIF paths, disabling pmdown_time
> allows switching to the optimal sample rate immediately, instead of
> after a 5 second delay.
> 
> Signed-off-by: Samuel Holland <samuel@sholland.org>

Acked-by: Maxime Ripard <mripard@kernel.org>

Thanks!
Maxime

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  reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-14  6:19 [PATCH v2 00/17] ASoC: sun8i-codec: support for AIF2 and AIF3 Samuel Holland
2020-10-14  6:19 ` [PATCH v2 01/17] ASoC: sun8i-codec: Prepare to extend the DAI driver Samuel Holland
2020-10-14  6:19 ` [PATCH v2 02/17] ASoC: sun8i-codec: Program DAI format before clock inversion Samuel Holland
2020-10-14  6:19 ` [PATCH v2 03/17] ASoC: sun8i-codec: Enable all supported clock inversions Samuel Holland
2020-10-19  8:24   ` Maxime Ripard
2020-10-14  6:19 ` [PATCH v2 04/17] ASoC: sun8i-codec: Use the provided word size Samuel Holland
2020-10-14  6:19 ` [PATCH v2 05/17] ASoC: sun8i-codec: Round up the LRCK divisor Samuel Holland
2020-10-14  6:19 ` [PATCH v2 06/17] ASoC: sun8i-codec: Correct the BCLK divisor calculation Samuel Holland
2020-10-14  6:19 ` [PATCH v2 07/17] ASoC: sun8i-codec: Support the TDM slot binding Samuel Holland
2020-10-14  6:19 ` [PATCH v2 08/17] ASoC: sun8i-codec: Enforce symmetric DAI parameters Samuel Holland
2020-10-14  6:19 ` [PATCH v2 09/17] ASoC: sun8i-codec: Enable all supported sample rates Samuel Holland
2020-10-14  6:19 ` [PATCH v2 10/17] ASoC: sun8i-codec: Automatically set the system sample rate Samuel Holland
2020-10-19  8:25   ` Maxime Ripard [this message]
2020-10-14  6:19 ` [PATCH v2 11/17] ASoC: sun8i-codec: Constrain to compatible sample rates Samuel Holland
2020-10-14  6:19 ` [PATCH v2 12/17] ASoC: sun8i-codec: Protect the clock rate while streams are open Samuel Holland
2020-10-19  8:28   ` Maxime Ripard
2020-10-14  6:19 ` [PATCH v2 13/17] ASoC: sun8i-codec: Require an exact BCLK divisor match Samuel Holland
2020-10-14  6:19 ` [PATCH v2 14/17] ASoC: sun8i-codec: Enable all supported PCM formats Samuel Holland
2020-10-14  6:19 ` [PATCH v2 15/17] ASoC: sun8i-codec: Generalize AIF clock control Samuel Holland
2020-10-19  8:56   ` Maxime Ripard
2020-10-14  6:19 ` [PATCH v2 16/17] ASoC: sun8i-codec: Add the AIF2 DAI, widgets, and routes Samuel Holland
2020-10-14  6:19 ` [PATCH v2 17/17] ASoC: sun8i-codec: Add the AIF3 " Samuel Holland
2020-10-15  3:24   ` Samuel Holland
2020-10-26 23:46 ` [PATCH v2 00/17] ASoC: sun8i-codec: support for AIF2 and AIF3 Mark Brown

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