[alsa-devel] [PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal to system freq

[Fabio Estevam]

[Sorry for the top-posting]


The driver currently has:


/*
* Hardware limitation: The bclk rate must be
* never greater than 1/5 IPG clock rate
*/
if (freq * 5 > clk_get_rate(ssi_private->clk)) {
dev_err(cpu_dai->dev, "bitclk > ipgclk/5\n");
return -EINVAL;
}


Isn't this properly taking care of the clock restriction?

________________________________
From: Lukasz Majewski <lukma at denx.de>
Sent: Sunday, September 3, 2017 8:05:01 AM
To: Timur Tabi; Nicolin Chen; Xiubo Li; Fabio Estevam; Liam Girdwood; Mark Brown; Jaroslav Kysela; Takashi Iwai
Cc: alsa-devel at alsa-project.org; linuxppc-dev at lists.ozlabs.org; linux-kernel at vger.kernel.org; Lukasz Majewski
Subject: [PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal to system freq

The problem is visible in the following setup (on the imx6q):
"simple-audio-card" -> ssi2 -> I2S + I2C -> codec

The function call log (simple-card probe -> CONFIG_SND_SIMPLE_CARD):

asoc_simple_card_init_dai() @ sound/soc/generic/simple-card-utils.c
snd_soc_dai_set_sysclk()
fsl_ssi_set_dai_sysclk() @ sound/soc/fsl/fsl_ssi.c

The last call is changing the bit clock (BCLK) frequency to SSI's IP
block clock (ipg = 66 MHz) [1].
This is wrong, since IMX SSI block requires the I2S BCLK to be less
than 1/5 of [1].

As a result the driver initialization passes without any errors, but the
speaker-test test case breaks.

This commit checks if the fsl_ssi_set_dai_sysclk() frequency passed is
not equal to [1].

Signed-off-by: Lukasz Majewski <lukma at denx.de>
---
 sound/soc/fsl/fsl_ssi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
index 173cb84..1186fa9 100644
--- a/sound/soc/fsl/fsl_ssi.c
+++ b/sound/soc/fsl/fsl_ssi.c
@@ -809,6 +809,8 @@ static int fsl_ssi_set_dai_sysclk(struct snd_soc_dai *cpu_dai,
                 int clk_id, unsigned int freq, int dir)
 {
         struct fsl_ssi_private *ssi_private = snd_soc_dai_get_drvdata(cpu_dai);
+       if (clk_get_rate(ssi_private->clk) == freq)
+               return 0;

         ssi_private->bitclk_freq = freq;

--
2.1.4