Hi Fabio,
[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; }
Unfortunately not.
This is the part of fsl_ssi_set_bclk() function which is called after fsl_ssi_set_dai_sysclk() (which sets ssi_private->bitclk_freq = freq;).
Before the aforementioned check we do have:
if (ssi_private->bitclk_freq) freq = ssi_private->bitclk_freq; else freq = params_channels(hw_params) * 32 * params_rate(hw_params);
Which assigns freq = bitclk_freq (66 MHz)
And then we break on this particular check:
66MHz * 5 > 66 MHz.
The culprit IMHO is the ssi_private->bitclk_freq = freq; in the fsl_ssi_set_dai_sysclk(), since we _should_ set SSI's IP block clock (ssi_private->clk), not the bit clock (BCLK).
This patch just quits early if it detects change, which don't need to be done.
Isn't this properly taking care of the clock restriction?
From: Lukasz Majewski lukma@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@alsa-project.org; linuxppc-dev@lists.ozlabs.org; linux-kernel@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@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