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Commit 255173b4 authored by Peter Meerwald's avatar Peter Meerwald Committed by Mark Brown
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ASoC: PLL computation in TLV320AIC3x SoC driver 

fix precision of PLL computation for TLV320AIC3x SoC driver,
test results are at http://pmeerw.net/clk



Signed-off-by: default avatarPeter Meerwald <pmeerw@pmeerw.net>
Acked-by: default avatarVladimir Barinov <vova.barinov@gmail.com>
Acked-by: default avatarLiam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
parent 3497b919

sound/soc/codecs/tlv320aic3x.c

+49 −26
Original line number Diff line number Diff line
@@ -765,9 +765,10 @@ static int aic3x_hw_params(struct snd_pcm_substream *substream, 
	struct snd_soc_codec *codec = socdev->card->codec;

	struct aic3x_priv *aic3x = codec->private_data;

	int codec_clk = 0, bypass_pll = 0, fsref, last_clk = 0;

	u8 data, r, p, pll_q, pll_p = 1, pll_r = 1, pll_j = 1;

	u16 pll_d = 1;

	u8 data, j, r, p, pll_q, pll_p = 1, pll_r = 1, pll_j = 1;

	u16 d, pll_d = 1;

	u8 reg;

	int clk;



	/* select data word length */

	data =
@@ -833,41 +834,62 @@ static int aic3x_hw_params(struct snd_pcm_substream *substream, 
	if (bypass_pll)

		return 0;



	/* Use PLL

	 * find an apropriate setup for j, d, r and p by iterating over

	 * p and r - j and d are calculated for each fraction.

	 * Up to 128 values are probed, the closest one wins the game.

	/* Use PLL, compute apropriate setup for j, d, r and p, the closest

	 * one wins the game. Try with d==0 first, next with d!=0.

	 * Constraints for j are according to the datasheet.

	 * The sysclk is divided by 1000 to prevent integer overflows.

	 */



	codec_clk = (2048 * fsref) / (aic3x->sysclk / 1000);



	for (r = 1; r <= 16; r++)

		for (p = 1; p <= 8; p++) {

			int clk, tmp = (codec_clk * pll_r * 10) / pll_p;

			u8 j = tmp / 10000;

			u16 d = tmp % 10000;

			for (j = 4; j <= 55; j++) {

				/* This is actually 1000*((j+(d/10000))*r)/p

				 * The term had to be converted to get

				 * rid of the division by 10000; d = 0 here

				 */

				int clk = (1000 * j * r) / p;



			if (j > 63)

				continue;

				/* Check whether this values get closer than

				 * the best ones we had before

				 */

				if (abs(codec_clk - clk) <

					abs(codec_clk - last_clk)) {

					pll_j = j; pll_d = 0;

					pll_r = r; pll_p = p;

					last_clk = clk;

				}



			if (d != 0 && aic3x->sysclk < 10000000)

				/* Early exit for exact matches */

				if (clk == codec_clk)

					goto found;

			}

		}



	/* try with d != 0 */

	for (p = 1; p <= 8; p++) {

		j = codec_clk * p / 1000;



		if (j < 4 || j > 11)

			continue;



			/* This is actually 1000 * ((j + (d/10000)) * r) / p

			 * The term had to be converted to get rid of the

			 * division by 10000 */

			clk = ((10000 * j * r) + (d * r)) / (10 * p);

		/* do not use codec_clk here since we'd loose precision */

		d = ((2048 * p * fsref) - j * aic3x->sysclk)

			* 100 / (aic3x->sysclk/100);



		clk = (10000 * j + d) / (10 * p);



		/* check whether this values get closer than the best

		 * ones we had before */

		if (abs(codec_clk - clk) < abs(codec_clk - last_clk)) {

				pll_j = j; pll_d = d; pll_r = r; pll_p = p;

			pll_j = j; pll_d = d; pll_r = 1; pll_p = p;

			last_clk = clk;

		}



		/* Early exit for exact matches */

		if (clk == codec_clk)

				break;

			goto found;

	}



	if (last_clk == 0) {
@@ -875,6 +897,7 @@ static int aic3x_hw_params(struct snd_pcm_substream *substream, 
		return -EINVAL;

	}



found:

	data = aic3x_read_reg_cache(codec, AIC3X_PLL_PROGA_REG);

	aic3x_write(codec, AIC3X_PLL_PROGA_REG, data | (pll_p << PLLP_SHIFT));

	aic3x_write(codec, AIC3X_OVRF_STATUS_AND_PLLR_REG, pll_r << PLLR_SHIFT);