[PATCH] ASoC: pcm512x: Mend accesses to the I2S_1 and I2S_2 registers

[Péter Ujfalusi]

Hi Peter.

On 20/09/2021 22:37, Peter Rosin wrote:

> Nope, MODE1/2 are wired for I2C -> FMT is just the last I2C address
> bit. So, nothing to do with I2S. And I can't see how that would explain
> the same problem with the I2S_2 register?

true, but worth the question ;)
 
>>> This fix is not 100% correct. The datasheet of at least the pcm5142
>>> states that four bits (0xcc) in the I2S_1 register are "RSV"
>>> ("Reserved. Do not access.") and no hint is given as to what theHi
>>> initial values are supposed to be. So, specifying defaults for
>>> these bits is wrong. But perhaps better than a broken driver?
>>
>> The default of 0x02 (AFMT = 00b - I2S, ALEN = 10b - 24bits) is correct
>> for I2S_1 and the 0 is the default of I2S_2.
>>
>> The failure happens when updating the AFMT (bit4-5) and when regmap is
>> doing a i2c read since the default is not specified.
>>
>> It would be interesting to see what it is reading... Out of interest:
>> can you mar the I2S_1 and I2S_2 as volatile and read / print the value
>> just before the afmt and alen update?
> 
> My first attempt was to mark the register volatile, and then read and
> compare if the update was needed at all. But marking volatile wasn't
> enough.

If the value is not provided in the defaults then the first read is reading out to the chip anyways.

> I also tried to set both a default and mark as volatile,

Volatile always skips the cache, default would be ignored.

> but it seems every read fails with -16 (EBUSY). I don't get why, to me
> it almost feels like a regmap issue of some sort (probably the regmap
> config is bad in some way), but I'm not fluent in regmap...

Or most likely the chip is not powered at pcm512x_set_fmt() time?

> So, since I can't read, I can't get to the initial values of the four
> reserved bits. So, I winged them as zero.

The value of the reserved bits are don't care.

Can you try the attached patch w/o without the defaults for i2s_1/2?
Not even compile tested...

>From e013a03286b6a744914c50239d3123b7723068df Mon Sep 17 00:00:00 2001
From: Peter Ujfalusi <peter.ujfalusi at gmail.com>
Date: Tue, 21 Sep 2021 07:12:06 +0300
Subject: [PATCH] ASoC: pcm512x: test regmap register accesses

read i2c_1 in different stages.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi at gmail.com>
---
 sound/soc/codecs/pcm512x.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/sound/soc/codecs/pcm512x.c b/sound/soc/codecs/pcm512x.c
index 4dc844f3c1fc..d0382e9ac329 100644
--- a/sound/soc/codecs/pcm512x.c
+++ b/sound/soc/codecs/pcm512x.c
@@ -1166,6 +1166,7 @@ static int pcm512x_hw_params(struct snd_pcm_substream *substream,
 {
 	struct snd_soc_component *component = dai->component;
 	struct pcm512x_priv *pcm512x = snd_soc_component_get_drvdata(component);
+	unsigned int val;
 	int alen;
 	int gpio;
 	int ret;
@@ -1193,6 +1194,18 @@ static int pcm512x_hw_params(struct snd_pcm_substream *substream,
 		return -EINVAL;
 	}
 
+	ret = regmap_read(pcm512x->regmap, PCM512x_I2S_1, &val);
+	if (ret) {
+		dev_err(component->dev, "%s: failed to read I2S_1: %d\n", __func_, ret);
+		ret = regmap_read(pcm512x->regmap, PCM512x_PLL_EN, &val);
+		if (ret)
+			dev_err(component->dev, "%s: failed to read PLL_EN: %d\n", __func__, ret);
+		else
+			dev_err(component->dev, "%s: PLL_EN: %#x\n", __func__, val);
+	} else {
+		dev_err(component->dev, "%s: I2S_1: %#x\n", __func__, val);
+	}
+
 	ret = regmap_update_bits(pcm512x->regmap, PCM512x_I2S_1,
 				 PCM512x_ALEN, alen);
 	if (ret != 0) {
@@ -1335,6 +1348,7 @@ static int pcm512x_set_fmt(struct snd_soc_dai *dai, unsigned int fmt)
 {
 	struct snd_soc_component *component = dai->component;
 	struct pcm512x_priv *pcm512x = snd_soc_component_get_drvdata(component);
+	unsigned int val;
 	int afmt;
 	int offset = 0;
 	int clock_output;
@@ -1396,18 +1410,28 @@ static int pcm512x_set_fmt(struct snd_soc_dai *dai, unsigned int fmt)
 		return -EINVAL;
 	}
 
+	ret = regmap_read(pcm512x->regmap, PCM512x_I2S_1, &val);
+	if (ret) {
+		dev_err(component->dev, "%s: failed to read I2S_1: %d\n", __func_, ret);
+		ret = regmap_read(pcm512x->regmap, PCM512x_PLL_EN, &val);
+		if (ret)
+			dev_err(component->dev, "%s: failed to read PLL_EN: %d\n", __func__, ret);
+		else
+			dev_err(component->dev, "%s: PLL_EN: %#x\n", __func__, val);
+	} else {
+		dev_err(component->dev, "%s: I2S_1: %#x\n", __func__, val);
+	}
+
 	ret = regmap_update_bits(pcm512x->regmap, PCM512x_I2S_1,
 				 PCM512x_AFMT, afmt);
 	if (ret != 0) {
 		dev_err(component->dev, "Failed to set data format: %d\n", ret);
-		return ret;
 	}
 
 	ret = regmap_update_bits(pcm512x->regmap, PCM512x_I2S_2,
 				 0xFF, offset);
 	if (ret != 0) {
 		dev_err(component->dev, "Failed to set data offset: %d\n", ret);
-		return ret;
 	}
 
 	pcm512x->fmt = fmt;
-- 
2.33.0



-- 
Péter
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