Commit 6c8ca30e authored Mar 04, 2015 by Nicolin Chen Committed by Mark Brown Mar 05, 2015

ASoC: fsl_ssi: Don't try to round-up for PM divisor calculation



According to i.MX6 Series Reference Manual, the formula to calculate
the sys clock is

sysclk rate = bclk rate * (div2 + 1) * (7 * psr + 1) * (pm + 1) * 2

Commit aafa85e7 ("ASoC: fsl_ssi: Add DAI master mode support for
SSI on i.MX series") added the divisor calculation which relies on
the clk_round_rate(). However, at that time, clk_round_rate() didn't
provide closest clock rates for some cases because it might not use
a correct rounding policy. So using the original formula (pm + 1) for
PM divisor was not able to give us a desired clock rate. And then we
used (pm + 2) to do the trick.

However, the clk-divider driver has been refined a lot since commit
b11d282d ("clk: divider: fix rate calculation for fractional rates")
Now using (pm + 2) trick would result an incorrect clock rate.

So this patch fixes the problem by removing the useless trick.

Reported-by: Stephane Cerveau <scerveau@voxtok.com>
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

parent 90aff15b

sound/soc/fsl/fsl_ssi.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -603,7 +603,7 @@ static int fsl_ssi_set_bclk(struct snd_pcm_substream *substream,
	factor = (div2 + 1) * (7 * psr + 1) * 2;		factor = (div2 + 1) * (7 * psr + 1) * 2;

	for (i = 0; i < 255; i++) {		for (i = 0; i < 255; i++) {
	tmprate = freq * factor * (i + 2);		tmprate = freq * factor * (i + 1);

	if (baudclk_is_used)		if (baudclk_is_used)
	clkrate = clk_get_rate(ssi_private->baudclk);		clkrate = clk_get_rate(ssi_private->baudclk);