[PATCH v2 0/2] wm8960: Relax bit clock computation

[PATCH v2 0/2] wm8960: Relax bit clock computation

[Daniel Baluta]

This patch series allows playing S20_3LE .wav samples with 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.

Changes since v1:
	* dropped the RFC tag
	* comments in each individual patch
	
Daniel Baluta (2):
  ASoC: codec: wm8960: Refactor sysclk freq search
  ASoC: codec: wm8960: Relax bit clock computation

 sound/soc/codecs/wm8960.c | 119 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 97 insertions(+), 22 deletions(-)

-- 
2.7.4

[PATCH v2 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>
---
Changes since v1:
	* made wm8960_configure_sysclk static
	* renamed i, j, with sysclk_idx, dac_idx, bclk_idx
	* added brackets to if() branch
	* kept the update of (sysclk_idx, ...) inside "for" loop
	because next patch requires (sysclk_idx, ..) to be saved
	inside loop

 sound/soc/codecs/wm8960.c | 80 ++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 61 insertions(+), 19 deletions(-)

diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c
index 3bf081a..25a4a11 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
+ * @sysclk_idx: sysclk_divs index for found sysclk
+ * @dac_idx: dac_divs index for found lrclk
+ * @bclk_idx: bclk_divs index for found bclk
+ *
+ * Returns:
+ * -1, in case no sysclk frequency available found
+ *  0, in case an exact (@sysclk_idx, @dac_idx, @bclk_idx) match is found
+ */
+static
+int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
+			    int *sysclk_idx, int *dac_idx, int *bclk_idx)
+{
+	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) {
+					*sysclk_idx = i;
+					*dac_idx = j;
+					*bclk_idx = 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,
@@ -643,25 +702,8 @@ 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) {
 			dev_err(codec->dev, "failed to configure clock\n");
-- 
2.7.4

Re: [PATCH v2 1/2] ASoC: codec: wm8960: Refactor sysclk freq search

[Charles Keepax]

On Tue, Mar 21, 2017 at 12:09:35PM +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>
> ---

Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>

Thanks,
Charles

Applied "ASoC: codec: wm8960: Refactor sysclk freq search" to the asoc tree

[Mark Brown]

The patch

   ASoC: codec: wm8960: Refactor sysclk freq search

has been applied to the asoc tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From 3ddc97211cbb61a5f59882c26f8e3158c86e34bb Mon Sep 17 00:00:00 2001
From: Daniel Baluta <daniel.baluta@nxp.com>
Date: Tue, 21 Mar 2017 17:03:24 +0200
Subject: [PATCH] ASoC: codec: wm8960: Refactor sysclk freq search

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>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 sound/soc/codecs/wm8960.c | 80 ++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 61 insertions(+), 19 deletions(-)

diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c
index 3bf081a7e450..25a4a11929fe 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
+ * @sysclk_idx: sysclk_divs index for found sysclk
+ * @dac_idx: dac_divs index for found lrclk
+ * @bclk_idx: bclk_divs index for found bclk
+ *
+ * Returns:
+ * -1, in case no sysclk frequency available found
+ *  0, in case an exact (@sysclk_idx, @dac_idx, @bclk_idx) match is found
+ */
+static
+int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
+			    int *sysclk_idx, int *dac_idx, int *bclk_idx)
+{
+	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) {
+					*sysclk_idx = i;
+					*dac_idx = j;
+					*bclk_idx = 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,
@@ -643,25 +702,8 @@ 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) {
 			dev_err(codec->dev, "failed to configure clock\n");
-- 
2.11.0

[PATCH v2 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>
---
Changes since v1:
	* use a marker to check if a match is found
	* didn't removed PLL as Charles suggested because there is
	a special PLL mode which explictly uses PLL. We could start
	a discussion on not using PLL when deriving bitclk, but this
	is to be done in another patch.

 sound/soc/codecs/wm8960.c | 43 ++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 38 insertions(+), 5 deletions(-)

diff --git a/sound/soc/codecs/wm8960.c b/sound/soc/codecs/wm8960.c
index 25a4a11..ce4fcd0 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
  * @sysclk_idx: sysclk_divs index for found sysclk
@@ -620,6 +624,7 @@ static const int bclk_divs[] = {
  * Returns:
  * -1, in case no sysclk frequency available found
  *  0, in case an exact (@sysclk_idx, @dac_idx, @bclk_idx) match is found
+ * >0, in case a relaxed (@sysclk_idx, @dac_idx, @bclk_idx) match is found
  */
 static
 int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
@@ -627,7 +632,10 @@ int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
 {
 	int sysclk, bclk, lrclk;
 	int i, j, k;
-	int diff;
+	int diff, closest = mclk;
+
+	/* marker for no match */
+	*bclk_idx = -1;
 
 	bclk = wm8960->bclk;
 	lrclk = wm8960->lrclk;
@@ -648,6 +656,12 @@ int wm8960_configure_sysclk(struct wm8960_priv *wm8960, int mclk,
 					*bclk_idx = k;
 					break;
 				}
+				if (diff > 0 && closest > diff) {
+					*sysclk_idx = i;
+					*dac_idx = j;
+					*bclk_idx = k;
+					closest = diff;
+				}
 			}
 			if (k != ARRAY_SIZE(bclk_divs))
 				break;
@@ -656,10 +670,16 @@ 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 (*bclk_idx == -1)
+		return -1;
+
+	/* relaxed match */
+	return 1;
 }
 
 static int wm8960_configure_clocking(struct snd_soc_codec *codec)
@@ -668,6 +688,7 @@ 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 +726,16 @@ 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 in case no PLL out avail */
+		if (ret > 0) {
+			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 +763,14 @@ 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: [PATCH v2 2/2] ASoC: codec: wm8960: Relax bit clock computation

[Charles Keepax]

On Tue, Mar 21, 2017 at 12:09:36PM +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>
> ---
> Changes since v1:
> 	* use a marker to check if a match is found
> 	* didn't removed PLL as Charles suggested because there is
> 	a special PLL mode which explictly uses PLL. We could start
> 	a discussion on not using PLL when deriving bitclk, but this
> 	is to be done in another patch.
> 

Could you elaborate on this a little more am I not sure I follow
100%? There is a mode which explictly requires the PLL to be used
(WM8960_SYSCLK_PLL) but in that case your wm8960_configure_sysclk
code will not be called so I don't see what is causing that to have
an effect on this patch?

Thanks,
Charles

Re: [PATCH v2 2/2] ASoC: codec: wm8960: Relax bit clock computation

[Daniel Baluta]

On Tue, Mar 21, 2017 at 2:52 PM, Charles Keepax
<ckeepax@opensource.wolfsonmicro.com> wrote:
> On Tue, Mar 21, 2017 at 12:09:36PM +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>
>> ---
>> Changes since v1:
>>       * use a marker to check if a match is found
>>       * didn't removed PLL as Charles suggested because there is
>>       a special PLL mode which explictly uses PLL. We could start
>>       a discussion on not using PLL when deriving bitclk, but this
>>       is to be done in another patch.
>>
>
> Could you elaborate on this a little more am I not sure I follow
> 100%? There is a mode which explictly requires the PLL to be used
> (WM8960_SYSCLK_PLL) but in that case your wm8960_configure_sysclk
> code will not be called so I don't see what is causing that to have
> an effect on this patch?

My doubt is, what happens if wm8960_configure_clocking is called with
wm8960->clk_id = WM8960_SYSCLK_PLL and we remove the PLL
as suggested.

Is this possible even possible?

Anyhow, I noticed that so far wm8960->clk_id is never set to
WM8960_SYSCLK_PLL :).

So, my proposal is to merge this patch which improves the existing code and deal
with PLL fallback in a separate patch later.

I am afraid of touching things which I don't understand how they work :D.

thanks,
Daniel.

Re: [PATCH v2 2/2] ASoC: codec: wm8960: Relax bit clock computation

[Charles Keepax]

On Tue, Mar 21, 2017 at 04:05:15PM +0200, Daniel Baluta wrote:
> On Tue, Mar 21, 2017 at 2:52 PM, Charles Keepax
> <ckeepax@opensource.wolfsonmicro.com> wrote:
> > On Tue, Mar 21, 2017 at 12:09:36PM +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>
> >> ---
> >> Changes since v1:
> >>       * use a marker to check if a match is found
> >>       * didn't removed PLL as Charles suggested because there is
> >>       a special PLL mode which explictly uses PLL. We could start
> >>       a discussion on not using PLL when deriving bitclk, but this
> >>       is to be done in another patch.
> >>
> >
> > Could you elaborate on this a little more am I not sure I follow
> > 100%? There is a mode which explictly requires the PLL to be used
> > (WM8960_SYSCLK_PLL) but in that case your wm8960_configure_sysclk
> > code will not be called so I don't see what is causing that to have
> > an effect on this patch?
> 
> My doubt is, what happens if wm8960_configure_clocking is called with
> wm8960->clk_id = WM8960_SYSCLK_PLL and we remove the PLL
> as suggested.

I wasn't suggesting removing the PLL just that if we find a
"relaxed match" we don't need to then check the PLL for a better
match, as I suspect that a slightly higher than needed bit clock
has less power/performance impact than firing up the PLL.

Which removes the need to differenciate between a relaxed and
bang on match in wm8960_configure_sysclk and means you don't have
to do the caching the values across the PLL code that you do now.

Thanks,
Charles

Re: [PATCH v2 2/2] ASoC: codec: wm8960: Relax bit clock computation

[Daniel Baluta]

On Tue, Mar 21, 2017 at 4:20 PM, Charles Keepax
<ckeepax@opensource.wolfsonmicro.com> wrote:
> On Tue, Mar 21, 2017 at 04:05:15PM +0200, Daniel Baluta wrote:
>> On Tue, Mar 21, 2017 at 2:52 PM, Charles Keepax
>> <ckeepax@opensource.wolfsonmicro.com> wrote:
>> > On Tue, Mar 21, 2017 at 12:09:36PM +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>
>> >> ---
>> >> Changes since v1:
>> >>       * use a marker to check if a match is found
>> >>       * didn't removed PLL as Charles suggested because there is
>> >>       a special PLL mode which explictly uses PLL. We could start
>> >>       a discussion on not using PLL when deriving bitclk, but this
>> >>       is to be done in another patch.
>> >>
>> >
>> > Could you elaborate on this a little more am I not sure I follow
>> > 100%? There is a mode which explictly requires the PLL to be used
>> > (WM8960_SYSCLK_PLL) but in that case your wm8960_configure_sysclk
>> > code will not be called so I don't see what is causing that to have
>> > an effect on this patch?
>>
>> My doubt is, what happens if wm8960_configure_clocking is called with
>> wm8960->clk_id = WM8960_SYSCLK_PLL and we remove the PLL
>> as suggested.
>
> I wasn't suggesting removing the PLL just that if we find a
> "relaxed match" we don't need to then check the PLL for a better
> match, as I suspect that a slightly higher than needed bit clock
> has less power/performance impact than firing up the PLL.
>
> Which removes the need to differenciate between a relaxed and
> bang on match in wm8960_configure_sysclk and means you don't have
> to do the caching the values across the PLL code that you do now.

Oh, I see. So we still use the PLL when no exact or relaxed match
is found.

Re: [PATCH v2 2/2] ASoC: codec: wm8960: Relax bit clock computation

[Charles Keepax]

On Tue, Mar 21, 2017 at 04:25:40PM +0200, Daniel Baluta wrote:
> On Tue, Mar 21, 2017 at 4:20 PM, Charles Keepax
> <ckeepax@opensource.wolfsonmicro.com> wrote:
> > On Tue, Mar 21, 2017 at 04:05:15PM +0200, Daniel Baluta wrote:
> >> On Tue, Mar 21, 2017 at 2:52 PM, Charles Keepax
> >> <ckeepax@opensource.wolfsonmicro.com> wrote:
> >> > On Tue, Mar 21, 2017 at 12:09:36PM +0200, Daniel Baluta wrote:
> >> >>       * use a marker to check if a match is found
> >> >>       * didn't removed PLL as Charles suggested because there is
> >> >>       a special PLL mode which explictly uses PLL. We could start
> >> >>       a discussion on not using PLL when deriving bitclk, but this
> >> >>       is to be done in another patch.
> >> >>
> >> >
> >> > Could you elaborate on this a little more am I not sure I follow
> >> > 100%? There is a mode which explictly requires the PLL to be used
> >> > (WM8960_SYSCLK_PLL) but in that case your wm8960_configure_sysclk
> >> > code will not be called so I don't see what is causing that to have
> >> > an effect on this patch?
> >>
> >> My doubt is, what happens if wm8960_configure_clocking is called with
> >> wm8960->clk_id = WM8960_SYSCLK_PLL and we remove the PLL
> >> as suggested.
> >
> > I wasn't suggesting removing the PLL just that if we find a
> > "relaxed match" we don't need to then check the PLL for a better
> > match, as I suspect that a slightly higher than needed bit clock
> > has less power/performance impact than firing up the PLL.
> >
> > Which removes the need to differenciate between a relaxed and
> > bang on match in wm8960_configure_sysclk and means you don't have
> > to do the caching the values across the PLL code that you do now.
> 
> Oh, I see. So we still use the PLL when no exact or relaxed match
> is found.

Yeah exactly or in the case that it is requested directly.

Thanks,
Charles