linux-kernel - Re: [PATCH v2 2/4] ASoC: es8316: Enable support for MCLK div by 2

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Date:   Mon, 28 Aug 2023 19:09:56 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Marian Postevca <posteuca@...ex.one>
Cc:     Takashi Iwai <tiwai@...e.com>, Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] ASoC: es8316: Enable support for MCLK div by 2

On Mon, Aug 28, 2023 at 12:50:45AM +0300, Marian Postevca wrote:
> Mark Brown <broonie@...nel.org> writes:

> > machine with this MCLK rather than that's based on the spec.  I would
> > instead suggest applying the MCLK divider in any case where we can do so
> > and still generate suitable clocking for the rest of the system, or at
> > least hit 256fs (the datasheet quotes 256/384fs on the front page which
> > suggests it's targetting 256fs, that'd be a fairly normal number, and
> > there's mention of 12/24MHz USB clocks being directly usable).  Doing
> > this should either make no odds or result in better performance.

> Not 100% sure what checks should be done for a MCLK to determine if it
> generates suitable clocking. Would something along this patch make
> sense?

In general a MCLK that allows you to configure the dividers in the CODEC
appropriately for use.  So long as it works your change looks fine I
think modulo.

> +	do {
> +		/* Validate supported sample rates that are autodetected from MCLK */
> +		for (i = 0; i < NR_SUPPORTED_MCLK_LRCK_RATIOS; i++) {
> +			const unsigned int ratio = supported_mclk_lrck_ratios[i];
> +
> +			if (clk % ratio != 0)
> +				continue;
> +			if (clk / ratio == params_rate(params))
> +				break;
> +		}

Use ARRAY_SIZE()

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