[RFC PATCH 0/2] wm8960: Relax bit clock computation

[RFC PATCH 0/2] wm8960: Relax bit clock computation

[Daniel Baluta]

This patch series allows running S20_3LE encoded samples on wm8960 codec.

First patch does a small refactoring of sysclk frequency search because
wm8960_configure_sysclk was getting pretty convoluted.

The second patch allows relaxing bitclock computation in the way that
if an exact bitclk couldn't be derived from sysclk it chooses the
smalles available bitclk greater than the desired bitclk.

For a better reviewing experience you can checked the squashed version
of this patches here:

http://pastebin.com/gBJ3DBSu

Note that this is a follow up of:

"ASoC: wm8960: Use physical width for bclk"

discussion archived here:

http://mailman.alsa-project.org/pipermail/alsa-devel/2017-March/118735.html

Daniel Baluta (2):
  ASoC: codec: wm8960: Refactor sysclk freq search
  ASoC: codec: wm8960: Relax bit clock computation

 sound/soc/codecs/wm8960.c | 113 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 91 insertions(+), 22 deletions(-)

-- 
2.7.4

[RFC PATCH 1/2] ASoC: codec: wm8960: Refactor sysclk freq search

[Daniel Baluta]

Add a separate function for finding (sysclk, lrclk, bclk)
when the clock is auto or mclk. This makes code easier to
read and reduces the indentation level in wm8960_configure_clocking.

Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
---
 sound/soc/codecs/wm8960.c | 82 +++++++++++++++++++++++++++++++++++------------
 1 file changed, 62 insertions(+), 20 deletions(-)

diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c
index 3bf081a..cb2ff2d 100644
--- a/sound/soc/codecs/wm8960.c
+++ b/sound/soc/codecs/wm8960.c
@@ -604,12 +604,71 @@ static const int bclk_divs[] = {
 	120, 160, 220, 240, 320, 320, 320
 };
 
+/**
+ * wm8960_configure_sysclk - checks if there is a sysclk frequency available
+ *	The sysclk must be chosen such that:
+ *		- sysclk     = MCLK / sysclk_divs
+ *		- lrclk      = sysclk / dac_divs
+ *		- 10 * bclk  = sysclk / bclk_divs
+ *
+ * @wm8960_priv: wm8960 codec private data
+ * @mclk: MCLK used to derive sysclk
+ * @_i: sysclk_divs index for found sysclk
+ * @_j: dac_divs index for found lrclk
+ * @_k: bclk_divs index for found bclk
+ *
+ * Returns:
+ * -1, in case no sysclk frequency available found
+ *  0, in case an exact match is found. See @_i, @_j, @_k
+ *
+ */
+int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
+		      int *_i, int *_j, int *_k)
+{
+	int sysclk, bclk, lrclk;
+	int i, j, k;
+	int diff;
+
+	bclk = wm8960->bclk;
+	lrclk = wm8960->lrclk;
+
+	/* check if the sysclk frequency is available. */
+	for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
+		if (sysclk_divs[i] == -1)
+			continue;
+		sysclk = mclk / sysclk_divs[i];
+		for (j = 0; j < ARRAY_SIZE(dac_divs); ++j) {
+			if (sysclk != dac_divs[j] * lrclk)
+				continue;
+			for (k = 0; k < ARRAY_SIZE(bclk_divs); ++k) {
+				diff = sysclk - bclk * bclk_divs[k] / 10;
+				if (diff == 0) {
+					*_i = i;
+					*_j = j;
+					*_k = k;
+					break;
+				}
+			}
+			if (k != ARRAY_SIZE(bclk_divs))
+				break;
+		}
+		if (j != ARRAY_SIZE(dac_divs))
+			break;
+	}
+
+	if (i != ARRAY_SIZE(sysclk_divs))
+		return 0;
+
+	return -1;
+}
+
 static int wm8960_configure_clocking(struct snd_soc_codec *codec)
 {
 	struct wm8960_priv *wm8960 = snd_soc_codec_get_drvdata(codec);
 	int sysclk, bclk, lrclk, freq_out, freq_in;
 	u16 iface1 = snd_soc_read(codec, WM8960_IFACE1);
 	int i, j, k;
+	int ret;
 
 	if (!(iface1 & (1<<6))) {
 		dev_dbg(codec->dev,
@@ -643,27 +702,10 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
 	}
 
 	if (wm8960->clk_id != WM8960_SYSCLK_PLL) {
-		/* check if the sysclk frequency is available. */
-		for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
-			if (sysclk_divs[i] == -1)
-				continue;
-			sysclk = freq_out / sysclk_divs[i];
-			for (j = 0; j < ARRAY_SIZE(dac_divs); ++j) {
-				if (sysclk != dac_divs[j] * lrclk)
-					continue;
-				for (k = 0; k < ARRAY_SIZE(bclk_divs); ++k)
-					if (sysclk == bclk * bclk_divs[k] / 10)
-						break;
-				if (k != ARRAY_SIZE(bclk_divs))
-					break;
-			}
-			if (j != ARRAY_SIZE(dac_divs))
-				break;
-		}
-
-		if (i != ARRAY_SIZE(sysclk_divs)) {
+		ret = wm8960_configure_sysclk(wm8960, freq_out, &i, &j, &k);
+		if (ret == 0)
 			goto configure_clock;
-		} else if (wm8960->clk_id != WM8960_SYSCLK_AUTO) {
+		else if (wm8960->clk_id != WM8960_SYSCLK_AUTO) {
 			dev_err(codec->dev, "failed to configure clock\n");
 			return -EINVAL;
 		}
-- 
2.7.4

Re: [RFC PATCH 1/2] ASoC: codec: wm8960: Refactor sysclk freq search

[Charles Keepax]

On Wed, Mar 15, 2017 at 05:33:05PM +0200, Daniel Baluta wrote:
> Add a separate function for finding (sysclk, lrclk, bclk)
> when the clock is auto or mclk. This makes code easier to
> read and reduces the indentation level in wm8960_configure_clocking.
> 
> Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
> ---
>  sound/soc/codecs/wm8960.c | 82 +++++++++++++++++++++++++++++++++++------------
>  1 file changed, 62 insertions(+), 20 deletions(-)
> 
> diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c
> index 3bf081a..cb2ff2d 100644
> --- a/sound/soc/codecs/wm8960.c
> +++ b/sound/soc/codecs/wm8960.c
> @@ -604,12 +604,71 @@ static const int bclk_divs[] = {
>  	120, 160, 220, 240, 320, 320, 320
>  };
>  
> +/**
> + * wm8960_configure_sysclk - checks if there is a sysclk frequency available
> + *	The sysclk must be chosen such that:
> + *		- sysclk     = MCLK / sysclk_divs
> + *		- lrclk      = sysclk / dac_divs
> + *		- 10 * bclk  = sysclk / bclk_divs
> + *
> + * @wm8960_priv: wm8960 codec private data
> + * @mclk: MCLK used to derive sysclk
> + * @_i: sysclk_divs index for found sysclk
> + * @_j: dac_divs index for found lrclk
> + * @_k: bclk_divs index for found bclk
> + *
> + * Returns:
> + * -1, in case no sysclk frequency available found
> + *  0, in case an exact match is found. See @_i, @_j, @_k
> + *
> + */
> +int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
> +		      int *_i, int *_j, int *_k)

This probably wants to be static.

> +{
> +	int sysclk, bclk, lrclk;
> +	int i, j, k;
> +	int diff;
> +
> +	bclk = wm8960->bclk;
> +	lrclk = wm8960->lrclk;
> +
> +	/* check if the sysclk frequency is available. */
> +	for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
> +		if (sysclk_divs[i] == -1)
> +			continue;
> +		sysclk = mclk / sysclk_divs[i];
> +		for (j = 0; j < ARRAY_SIZE(dac_divs); ++j) {
> +			if (sysclk != dac_divs[j] * lrclk)
> +				continue;
> +			for (k = 0; k < ARRAY_SIZE(bclk_divs); ++k) {
> +				diff = sysclk - bclk * bclk_divs[k] / 10;
> +				if (diff == 0) {
> +					*_i = i;
> +					*_j = j;
> +					*_k = k;

I would be tempted to move these ...

> +					break;
> +				}
> +			}
> +			if (k != ARRAY_SIZE(bclk_divs))
> +				break;
> +		}
> +		if (j != ARRAY_SIZE(dac_divs))
> +			break;
> +	}
> +
> +	if (i != ARRAY_SIZE(sysclk_divs))
> +		return 0;
> +

Down here and give _i, _j, _k slightly more descriptive names, I
know the original code didn't have great names either but might
as well make things a bit nicer as we are factoring it out.

> +	return -1;
> +}
> +
>  static int wm8960_configure_clocking(struct snd_soc_codec *codec)
>  {
>  	struct wm8960_priv *wm8960 = snd_soc_codec_get_drvdata(codec);
>  	int sysclk, bclk, lrclk, freq_out, freq_in;
>  	u16 iface1 = snd_soc_read(codec, WM8960_IFACE1);
>  	int i, j, k;
> +	int ret;
>  
>  	if (!(iface1 & (1<<6))) {
>  		dev_dbg(codec->dev,
> @@ -643,27 +702,10 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
>  	}
>  
>  	if (wm8960->clk_id != WM8960_SYSCLK_PLL) {
> -		/* check if the sysclk frequency is available. */
> -		for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
> -			if (sysclk_divs[i] == -1)
> -				continue;
> -			sysclk = freq_out / sysclk_divs[i];
> -			for (j = 0; j < ARRAY_SIZE(dac_divs); ++j) {
> -				if (sysclk != dac_divs[j] * lrclk)
> -					continue;
> -				for (k = 0; k < ARRAY_SIZE(bclk_divs); ++k)
> -					if (sysclk == bclk * bclk_divs[k] / 10)
> -						break;
> -				if (k != ARRAY_SIZE(bclk_divs))
> -					break;
> -			}
> -			if (j != ARRAY_SIZE(dac_divs))
> -				break;
> -		}
> -
> -		if (i != ARRAY_SIZE(sysclk_divs)) {
> +		ret = wm8960_configure_sysclk(wm8960, freq_out, &i, &j, &k);
> +		if (ret == 0)
>  			goto configure_clock;
> -		} else if (wm8960->clk_id != WM8960_SYSCLK_AUTO) {
> +		else if (wm8960->clk_id != WM8960_SYSCLK_AUTO) {

If one clause of the if has brackets the other should too.

Otherwise, I think this looks fine.

Thanks,
Charles

Re: [RFC PATCH 1/2] ASoC: codec: wm8960: Refactor sysclk freq search

[Daniel Baluta]

On Wed, Mar 15, 2017 at 6:22 PM, Charles Keepax
<ckeepax@opensource.wolfsonmicro.com> wrote:
> On Wed, Mar 15, 2017 at 05:33:05PM +0200, Daniel Baluta wrote:
>> Add a separate function for finding (sysclk, lrclk, bclk)
>> when the clock is auto or mclk. This makes code easier to
>> read and reduces the indentation level in wm8960_configure_clocking.
>>
>> Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
>> ---
>>  sound/soc/codecs/wm8960.c | 82 +++++++++++++++++++++++++++++++++++------------
>>  1 file changed, 62 insertions(+), 20 deletions(-)
>>
>> diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c
>> index 3bf081a..cb2ff2d 100644
>> --- a/sound/soc/codecs/wm8960.c
>> +++ b/sound/soc/codecs/wm8960.c
>> @@ -604,12 +604,71 @@ static const int bclk_divs[] = {
>>       120, 160, 220, 240, 320, 320, 320
>>  };
>>
>> +/**
>> + * wm8960_configure_sysclk - checks if there is a sysclk frequency available
>> + *   The sysclk must be chosen such that:
>> + *           - sysclk     = MCLK / sysclk_divs
>> + *           - lrclk      = sysclk / dac_divs
>> + *           - 10 * bclk  = sysclk / bclk_divs
>> + *
>> + * @wm8960_priv: wm8960 codec private data
>> + * @mclk: MCLK used to derive sysclk
>> + * @_i: sysclk_divs index for found sysclk
>> + * @_j: dac_divs index for found lrclk
>> + * @_k: bclk_divs index for found bclk
>> + *
>> + * Returns:
>> + * -1, in case no sysclk frequency available found
>> + *  0, in case an exact match is found. See @_i, @_j, @_k
>> + *
>> + */
>> +int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
>> +                   int *_i, int *_j, int *_k)
>
> This probably wants to be static.

You are right. Will fix in next version.

>
>> +{
>> +     int sysclk, bclk, lrclk;
>> +     int i, j, k;
>> +     int diff;
>> +
>> +     bclk = wm8960->bclk;
>> +     lrclk = wm8960->lrclk;
>> +
>> +     /* check if the sysclk frequency is available. */
>> +     for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
>> +             if (sysclk_divs[i] == -1)
>> +                     continue;
>> +             sysclk = mclk / sysclk_divs[i];
>> +             for (j = 0; j < ARRAY_SIZE(dac_divs); ++j) {
>> +                     if (sysclk != dac_divs[j] * lrclk)
>> +                             continue;
>> +                     for (k = 0; k < ARRAY_SIZE(bclk_divs); ++k) {
>> +                             diff = sysclk - bclk * bclk_divs[k] / 10;
>> +                             if (diff == 0) {
>> +                                     *_i = i;
>> +                                     *_j = j;
>> +                                     *_k = k;
>
> I would be tempted to move these ...
>
>> +                                     break;
>> +                             }
>> +                     }
>> +                     if (k != ARRAY_SIZE(bclk_divs))
>> +                             break;
>> +             }
>> +             if (j != ARRAY_SIZE(dac_divs))
>> +                     break;
>> +     }
>> +
>> +     if (i != ARRAY_SIZE(sysclk_divs))
>> +             return 0;
>> +
>
> Down here and give _i, _j, _k slightly more descriptive names, I
> know the original code didn't have great names either but might
> as well make things a bit nicer as we are factoring it out.

Ok. This makes sense.

>
>> +     return -1;
>> +}
>> +
>>  static int wm8960_configure_clocking(struct snd_soc_codec *codec)
>>  {
>>       struct wm8960_priv *wm8960 = snd_soc_codec_get_drvdata(codec);
>>       int sysclk, bclk, lrclk, freq_out, freq_in;
>>       u16 iface1 = snd_soc_read(codec, WM8960_IFACE1);
>>       int i, j, k;
>> +     int ret;
>>
>>       if (!(iface1 & (1<<6))) {
>>               dev_dbg(codec->dev,
>> @@ -643,27 +702,10 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
>>       }
>>
>>       if (wm8960->clk_id != WM8960_SYSCLK_PLL) {
>> -             /* check if the sysclk frequency is available. */
>> -             for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
>> -                     if (sysclk_divs[i] == -1)
>> -                             continue;
>> -                     sysclk = freq_out / sysclk_divs[i];
>> -                     for (j = 0; j < ARRAY_SIZE(dac_divs); ++j) {
>> -                             if (sysclk != dac_divs[j] * lrclk)
>> -                                     continue;
>> -                             for (k = 0; k < ARRAY_SIZE(bclk_divs); ++k)
>> -                                     if (sysclk == bclk * bclk_divs[k] / 10)
>> -                                             break;
>> -                             if (k != ARRAY_SIZE(bclk_divs))
>> -                                     break;
>> -                     }
>> -                     if (j != ARRAY_SIZE(dac_divs))
>> -                             break;
>> -             }
>> -
>> -             if (i != ARRAY_SIZE(sysclk_divs)) {
>> +             ret = wm8960_configure_sysclk(wm8960, freq_out, &i, &j, &k);
>> +             if (ret == 0)
>>                       goto configure_clock;
>> -             } else if (wm8960->clk_id != WM8960_SYSCLK_AUTO) {
>> +             else if (wm8960->clk_id != WM8960_SYSCLK_AUTO) {
>
> If one clause of the if has brackets the other should too.

Ok.

thanks,
Daniel.

[RFC PATCH 2/2] ASoC: codec: wm8960: Relax bit clock computation

[Daniel Baluta]

WM8960 derives bit clock from sysclock using BCLKDIV[3:0] of R8
clocking register (See WM8960 datasheet, page 71).

There are use cases, like this:
aplay -Dhw:0,0 -r 48000 -c 1 -f S20_3LE -t raw audio48k20b_3LE1c.pcm

where no BCLKDIV applied to sysclock can give us the exact requested
bitclk, so driver fails to configure clocking and aplay fails to run.

Fix this by relaxing bitclk computation, so that when no exact value
can be derived from sysclk pick the closest value greater than
expected bitclk.

Suggested-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
---
 sound/soc/codecs/wm8960.c | 39 +++++++++++++++++++++++++++++++++------
 1 file changed, 33 insertions(+), 6 deletions(-)

diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c
index cb2ff2d..1669b45 100644
--- a/sound/soc/codecs/wm8960.c
+++ b/sound/soc/codecs/wm8960.c
@@ -611,6 +611,10 @@ static const int bclk_divs[] = {
  *		- lrclk      = sysclk / dac_divs
  *		- 10 * bclk  = sysclk / bclk_divs
  *
+ *	If we cannot find an exact match for (sysclk, lrclk, bclk)
+ *	triplet, we relax the bclk such that bclk is chosen as the
+ *	closest available frequency greater than expected bclk.
+ *
  * @wm8960_priv: wm8960 codec private data
  * @mclk: MCLK used to derive sysclk
  * @_i: sysclk_divs index for found sysclk
@@ -620,14 +624,14 @@ static const int bclk_divs[] = {
  * Returns:
  * -1, in case no sysclk frequency available found
  *  0, in case an exact match is found. See @_i, @_j, @_k
- *
+ * >0, in case a relaxed match is found. See @_i, @_j, @_k
  */
 int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
 		      int *_i, int *_j, int *_k)
 {
 	int sysclk, bclk, lrclk;
 	int i, j, k;
-	int diff;
+	int diff, closest = mclk;
 
 	bclk = wm8960->bclk;
 	lrclk = wm8960->lrclk;
@@ -648,6 +652,12 @@ int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
 					*_k = k;
 					break;
 				}
+				if (diff > 0 && closest > diff) {
+					*_i = i;
+					*_j = j;
+					*_k = k;
+					closest = diff;
+				}
 			}
 			if (k != ARRAY_SIZE(bclk_divs))
 				break;
@@ -656,10 +666,16 @@ int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
 			break;
 	}
 
+	/* exact match */
 	if (i != ARRAY_SIZE(sysclk_divs))
 		return 0;
 
-	return -1;
+	/* no match */
+	if (closest == mclk)
+		return -1;
+
+	/* relaxed match */
+	return 1;
 }
 
 static int wm8960_configure_clocking(struct snd_soc_codec *codec)
@@ -668,6 +684,7 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
 	int sysclk, bclk, lrclk, freq_out, freq_in;
 	u16 iface1 = snd_soc_read(codec, WM8960_IFACE1);
 	int i, j, k;
+	int best_sysclk_div, best_dac_div, best_bclk_div = -1;
 	int ret;
 
 	if (!(iface1 & (1<<6))) {
@@ -705,10 +722,14 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
 		ret = wm8960_configure_sysclk(wm8960, freq_out, &i, &j, &k);
 		if (ret == 0)
 			goto configure_clock;
-		else if (wm8960->clk_id != WM8960_SYSCLK_AUTO) {
+		else if (ret < 0 && wm8960->clk_id != WM8960_SYSCLK_AUTO) {
 			dev_err(codec->dev, "failed to configure clock\n");
 			return -EINVAL;
 		}
+		/* there is still hope, keep this if no PLL out available */
+		best_sysclk_div	= i;
+		best_dac_div	= j;
+		best_bclk_div	= k;
 	}
 	/* get a available pll out frequency and set pll */
 	for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
@@ -736,8 +757,14 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
 	}
 
 	if (i == ARRAY_SIZE(sysclk_divs)) {
-		dev_err(codec->dev, "failed to configure clock\n");
-		return -EINVAL;
+		if (best_bclk_div != -1) {
+			i = best_sysclk_div;
+			j = best_dac_div;
+			k = best_bclk_div;
+		} else {
+			dev_err(codec->dev, "failed to configure clock\n");
+			return -EINVAL;
+		}
 	}
 
 configure_clock:
-- 
2.7.4

Re: [RFC PATCH 2/2] ASoC: codec: wm8960: Relax bit clock computation

[Charles Keepax]

On Wed, Mar 15, 2017 at 05:33:06PM +0200, Daniel Baluta wrote:
> WM8960 derives bit clock from sysclock using BCLKDIV[3:0] of R8
> clocking register (See WM8960 datasheet, page 71).
> 
> There are use cases, like this:
> aplay -Dhw:0,0 -r 48000 -c 1 -f S20_3LE -t raw audio48k20b_3LE1c.pcm
> 
> where no BCLKDIV applied to sysclock can give us the exact requested
> bitclk, so driver fails to configure clocking and aplay fails to run.
> 
> Fix this by relaxing bitclk computation, so that when no exact value
> can be derived from sysclk pick the closest value greater than
> expected bitclk.
> 
> Suggested-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
> Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
> ---
>  sound/soc/codecs/wm8960.c | 39 +++++++++++++++++++++++++++++++++------
>  1 file changed, 33 insertions(+), 6 deletions(-)
> 
> diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c
> index cb2ff2d..1669b45 100644
> --- a/sound/soc/codecs/wm8960.c
> +++ b/sound/soc/codecs/wm8960.c
> @@ -611,6 +611,10 @@ static const int bclk_divs[] = {
>   *		- lrclk      = sysclk / dac_divs
>   *		- 10 * bclk  = sysclk / bclk_divs
>   *
> + *	If we cannot find an exact match for (sysclk, lrclk, bclk)
> + *	triplet, we relax the bclk such that bclk is chosen as the
> + *	closest available frequency greater than expected bclk.
> + *
>   * @wm8960_priv: wm8960 codec private data
>   * @mclk: MCLK used to derive sysclk
>   * @_i: sysclk_divs index for found sysclk
> @@ -620,14 +624,14 @@ static const int bclk_divs[] = {
>   * Returns:
>   * -1, in case no sysclk frequency available found
>   *  0, in case an exact match is found. See @_i, @_j, @_k
> - *
> + * >0, in case a relaxed match is found. See @_i, @_j, @_k
>   */
>  int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
>  		      int *_i, int *_j, int *_k)
>  {
>  	int sysclk, bclk, lrclk;
>  	int i, j, k;
> -	int diff;
> +	int diff, closest = mclk;

Don't you need to initialise diff here too?

>  
>  	bclk = wm8960->bclk;
>  	lrclk = wm8960->lrclk;
> @@ -648,6 +652,12 @@ int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
>  					*_k = k;
>  					break;
>  				}
> +				if (diff > 0 && closest > diff) {
> +					*_i = i;
> +					*_j = j;
> +					*_k = k;
> +					closest = diff;
> +				}
>  			}
>  			if (k != ARRAY_SIZE(bclk_divs))
>  				break;
> @@ -656,10 +666,16 @@ int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
>  			break;
>  	}
>  
> +	/* exact match */
>  	if (i != ARRAY_SIZE(sysclk_divs))
>  		return 0;
>  
> -	return -1;
> +	/* no match */
> +	if (closest == mclk)
> +		return -1;
> +
> +	/* relaxed match */
> +	return 1;

Do we need to differenciate between relaxed and an actual match?

>  }
>  
>  static int wm8960_configure_clocking(struct snd_soc_codec *codec)
> @@ -668,6 +684,7 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
>  	int sysclk, bclk, lrclk, freq_out, freq_in;
>  	u16 iface1 = snd_soc_read(codec, WM8960_IFACE1);
>  	int i, j, k;
> +	int best_sysclk_div, best_dac_div, best_bclk_div = -1;
>  	int ret;
>  
>  	if (!(iface1 & (1<<6))) {
> @@ -705,10 +722,14 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
>  		ret = wm8960_configure_sysclk(wm8960, freq_out, &i, &j, &k);
>  		if (ret == 0)
>  			goto configure_clock;
> -		else if (wm8960->clk_id != WM8960_SYSCLK_AUTO) {
> +		else if (ret < 0 && wm8960->clk_id != WM8960_SYSCLK_AUTO) {
>  			dev_err(codec->dev, "failed to configure clock\n");
>  			return -EINVAL;
>  		}
> +		/* there is still hope, keep this if no PLL out available */
> +		best_sysclk_div	= i;
> +		best_dac_div	= j;
> +		best_bclk_div	= k;

Enabling the PLL just to avoid running the BCLK a little fast
doesn't really seem worth it and it would make the code much more
obvious.

>  	}
>  	/* get a available pll out frequency and set pll */
>  	for (i = 0; i < ARRAY_SIZE(sysclk_divs); ++i) {
> @@ -736,8 +757,14 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
>  	}
>  
>  	if (i == ARRAY_SIZE(sysclk_divs)) {
> -		dev_err(codec->dev, "failed to configure clock\n");
> -		return -EINVAL;
> +		if (best_bclk_div != -1) {
> +			i = best_sysclk_div;
> +			j = best_dac_div;
> +			k = best_bclk_div;
> +		} else {
> +			dev_err(codec->dev, "failed to configure clock\n");
> +			return -EINVAL;
> +		}
>  	}
>  
>  configure_clock:
> -- 
> 2.7.4

Thanks,
Charles

Re: [RFC PATCH 2/2] ASoC: codec: wm8960: Relax bit clock computation

[Daniel Baluta]

On Wed, Mar 15, 2017 at 7:17 PM, Charles Keepax
<ckeepax@opensource.wolfsonmicro.com> wrote:
> On Wed, Mar 15, 2017 at 05:33:06PM +0200, Daniel Baluta wrote:
>> WM8960 derives bit clock from sysclock using BCLKDIV[3:0] of R8
>> clocking register (See WM8960 datasheet, page 71).
>>
>> There are use cases, like this:
>> aplay -Dhw:0,0 -r 48000 -c 1 -f S20_3LE -t raw audio48k20b_3LE1c.pcm
>>
>> where no BCLKDIV applied to sysclock can give us the exact requested
>> bitclk, so driver fails to configure clocking and aplay fails to run.
>>
>> Fix this by relaxing bitclk computation, so that when no exact value
>> can be derived from sysclk pick the closest value greater than
>> expected bitclk.
>>
>> Suggested-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
>> Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
>> ---
>>  sound/soc/codecs/wm8960.c | 39 +++++++++++++++++++++++++++++++++------
>>  1 file changed, 33 insertions(+), 6 deletions(-)
>>
>> diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c
>> index cb2ff2d..1669b45 100644
>> --- a/sound/soc/codecs/wm8960.c
>> +++ b/sound/soc/codecs/wm8960.c
>> @@ -611,6 +611,10 @@ static const int bclk_divs[] = {
>>   *           - lrclk      = sysclk / dac_divs
>>   *           - 10 * bclk  = sysclk / bclk_divs
>>   *
>> + *   If we cannot find an exact match for (sysclk, lrclk, bclk)
>> + *   triplet, we relax the bclk such that bclk is chosen as the
>> + *   closest available frequency greater than expected bclk.
>> + *
>>   * @wm8960_priv: wm8960 codec private data
>>   * @mclk: MCLK used to derive sysclk
>>   * @_i: sysclk_divs index for found sysclk
>> @@ -620,14 +624,14 @@ static const int bclk_divs[] = {
>>   * Returns:
>>   * -1, in case no sysclk frequency available found
>>   *  0, in case an exact match is found. See @_i, @_j, @_k
>> - *
>> + * >0, in case a relaxed match is found. See @_i, @_j, @_k
>>   */
>>  int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
>>                     int *_i, int *_j, int *_k)
>>  {
>>       int sysclk, bclk, lrclk;
>>       int i, j, k;
>> -     int diff;
>> +     int diff, closest = mclk;
>
> Don't you need to initialise diff here too?

It shouldn't be necessary. Diff is always initialized before used.
I added diff variable to avoid always writing: sysclk - bclk *
bclk_divs[k] / 10;


>
>>
>>       bclk = wm8960->bclk;
>>       lrclk = wm8960->lrclk;
>> @@ -648,6 +652,12 @@ int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
>>                                       *_k = k;
>>                                       break;
>>                               }
>> +                             if (diff > 0 && closest > diff) {
>> +                                     *_i = i;
>> +                                     *_j = j;
>> +                                     *_k = k;
>> +                                     closest = diff;
>> +                             }
>>                       }
>>                       if (k != ARRAY_SIZE(bclk_divs))
>>                               break;
>> @@ -656,10 +666,16 @@ int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
>>                       break;
>>       }
>>
>> +     /* exact match */
>>       if (i != ARRAY_SIZE(sysclk_divs))
>>               return 0;
>>
>> -     return -1;
>> +     /* no match */
>> +     if (closest == mclk)
>> +             return -1;
>> +
>> +     /* relaxed match */
>> +     return 1;
>
> Do we need to differenciate between relaxed and an actual match?

In my implementation yes. Because if an actual match happens we go directly
to "configure_clock" label. If a relaxed match happens we keep this in mind
for later and for now we try to see if a PLL out freq is available.

Finally, if no PLL out freq is available we go and use the "relaxed" match.


>>  }
>>
>>  static int wm8960_configure_clocking(struct snd_soc_codec *codec)
>> @@ -668,6 +684,7 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
>>       int sysclk, bclk, lrclk, freq_out, freq_in;
>>       u16 iface1 = snd_soc_read(codec, WM8960_IFACE1);
>>       int i, j, k;
>> +     int best_sysclk_div, best_dac_div, best_bclk_div = -1;
>>       int ret;
>>
>>       if (!(iface1 & (1<<6))) {
>> @@ -705,10 +722,14 @@ static int wm8960_configure_clocking(struct snd_soc_codec *codec)
>>               ret = wm8960_configure_sysclk(wm8960, freq_out, &i, &j, &k);
>>               if (ret == 0)
>>                       goto configure_clock;
>> -             else if (wm8960->clk_id != WM8960_SYSCLK_AUTO) {
>> +             else if (ret < 0 && wm8960->clk_id != WM8960_SYSCLK_AUTO) {
>>                       dev_err(codec->dev, "failed to configure clock\n");
>>                       return -EINVAL;
>>               }
>> +             /* there is still hope, keep this if no PLL out available */
>> +             best_sysclk_div = i;
>> +             best_dac_div    = j;
>> +             best_bclk_div   = k;
>
> Enabling the PLL just to avoid running the BCLK a little fast
> doesn't really seem worth it and it would make the code much more
> obvious.

That's a nice suggestion. With this we could remove the pll part. Not
sure if there
are any negative side effects.

I will do some tests.

thanks,
Daniel.