From: Nicolin Chen <nicoleotsuka@gmail.com>
To: broonie@kernel.org
Cc: alsa-devel@alsa-project.org, timur@tabi.org, tiwai@suse.de,
linux-kernel@vger.kernel.org, lgirdwood@gmail.com,
perex@perex.cz, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH] ASoC: fsl_ssi: Don't try to round-up for PM divisor calculation
Date: Wed, 4 Mar 2015 21:05:04 -0800 [thread overview]
Message-ID: <1425531904-3770-1-git-send-email-nicoleotsuka@gmail.com> (raw)
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 aafa85e71a75 ("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
b11d282dbea2 ("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>
---
sound/soc/fsl/fsl_ssi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
index 05575f4..6b0c8f7 100644
--- a/sound/soc/fsl/fsl_ssi.c
+++ b/sound/soc/fsl/fsl_ssi.c
@@ -603,7 +603,7 @@ static int fsl_ssi_set_bclk(struct snd_pcm_substream *substream,
factor = (div2 + 1) * (7 * psr + 1) * 2;
for (i = 0; i < 255; i++) {
- tmprate = freq * factor * (i + 2);
+ tmprate = freq * factor * (i + 1);
if (baudclk_is_used)
clkrate = clk_get_rate(ssi_private->baudclk);
--
1.9.1
next reply other threads:[~2015-03-05 5:05 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-05 5:05 Nicolin Chen [this message]
2015-03-05 12:23 ` [PATCH] ASoC: fsl_ssi: Don't try to round-up for PM divisor calculation Mark Brown
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