Re: [alsa-devel] [PATCH v3 09/18] ASoC: fsl-ssi: Only enable baudclk when used

Hi,

On Mon, Apr 14, 2014 at 11:28:51PM +0800, Nicolin Chen wrote:

On Mon, Apr 14, 2014 at 03:35:39PM +0200, Markus Pargmann wrote:

...

From: Sascha Hauer s.hauer@pengutronix.de

Enable baudclk only when it is used. The baudclock is only needed in master mode and only when thr driver is active, so move enabling to fsl_ssi_startup and disabling to fsl_ssi_shutdown.

Signed-off-by: Sascha Hauer s.hauer@pengutronix.de

sound/soc/fsl/fsl_ssi.c | 37 ++++++++++++++++++++++++++++++------- 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c index f2255cb..d6d3f0a3 100644 --- a/sound/soc/fsl/fsl_ssi.c +++ b/sound/soc/fsl/fsl_ssi.c @@ -236,6 +236,12 @@ static bool fsl_ssi_is_ac97(struct fsl_ssi_private *ssi_private) return !!(ssi_private->dai_fmt & SND_SOC_DAIFMT_AC97); }

+static bool fsl_ssi_is_i2s_master(struct fsl_ssi_private *ssi_private) +{

• return (ssi_private->dai_fmt & SND_SOC_DAIFMT_MASTER_MASK) ==

• SND_SOC_DAIFMT_CBS_CFS;
  

+}

/**

• fsl_ssi_isr: SSI interrupt handler

@@ -489,6 +495,7 @@ static int fsl_ssi_startup(struct snd_pcm_substream *substream, struct fsl_ssi_private *ssi_private = snd_soc_dai_get_drvdata(rtd->cpu_dai); unsigned long flags;

• int ret;

  if (!dai->active && !fsl_ssi_is_ac97(ssi_private)) { spin_lock_irqsave(&ssi_private->baudclk_lock, flags);

@@ -496,6 +503,12 @@ static int fsl_ssi_startup(struct snd_pcm_substream *substream, spin_unlock_irqrestore(&ssi_private->baudclk_lock, flags); }

• if (fsl_ssi_is_i2s_master(ssi_private)) {

• ret = clk_prepare_enable(ssi_private->baudclk);
  

• if (ret)
  

• 	return ret;
  

• }
• /* When using dual fifo mode, it is safer to ensure an even period
  • size. If appearing to an odd number while DMA always starts its
  • task from fifo0, fifo1 would be neglected at the end of each

@@ -508,6 +521,17 @@ static int fsl_ssi_startup(struct snd_pcm_substream *substream, return 0; }

+static void fsl_ssi_shutdown(struct snd_pcm_substream *substream,

• struct snd_soc_dai *dai)
  

+{

• struct snd_soc_pcm_runtime *rtd = substream->private_data;
• struct fsl_ssi_private *ssi_private =

• snd_soc_dai_get_drvdata(rtd->cpu_dai);
  

• if (fsl_ssi_is_i2s_master(ssi_private))

• clk_disable_unprepare(ssi_private->baudclk);
  

+}

/**

• fsl_ssi_hw_params - program the sample size

@@ -576,6 +600,11 @@ static int fsl_ssi_set_dai_fmt(struct snd_soc_dai *cpu_dai, unsigned int fmt)

ssi_private->dai_fmt = fmt;

• if (fsl_ssi_is_i2s_master(ssi_private) && IS_ERR(ssi_private->baudclk)) {

• dev_err(cpu_dai->dev, "no baudclk needed for master mode\n");
  

• return -EINVAL;
  

• }

I was wondering what if machine driver doesn't set fmt to master during its probe(), in another word -- before fsl_ssi_startup(), but leave that into its hw_params() via snd_soc_dai_set_fmt() which then would run after fsl_ssi_startup() while having no baud clock enabled in this case.

A better solution may be to wrap clk_prepare_enable() and master mode clock dividing code into fsl_ssi_hw_params(), a bit like the ESAI driver even though it doesn't contain the clk_prepare_enable() part currently, and then to put clk_disable_unprepare() into hw_free() for symmetry.

Any suggestion?

Yes this is a problem. Although I am not really convinced of the concept of setting up the DAIs in hw_params, we should support it as there are some users.

Is there always exactly one hw_free call for one hw_params call? There is a comment above the function: "Frees resources allocated by hw_params, can be called multiple times", so I am not sure if we can directly use clk_prepare_enable or if we need to remember the clock state?

Thanks,

Markus