[PATCH] ASoC: rockchip: i2s: fix playback after runtime resume

[PATCH] ASoC: rockchip: i2s: fix playback after runtime resume

[John Keeping]

When restoring registers during runtime resume, we must not write to
I2S_TXDR which is the transmit FIFO as this queues up a sample to be
output and pushes all of the output channels down by one.

This can be demonstrated with the speaker-test utility:

	for i in a b c; do speaker-test -c 2 -s 1; done

which should play a test through the left speaker three times but if the
I2S hardware starts runtime suspended the first sample will be played
through the right speaker.

Fix this by marking I2S_TXDR as volatile (which also requires marking it
as readble, even though it technically isn't).  This seems to be the
most robust fix, the alternative of giving I2S_TXDR a default value is
more fragile since it does not prevent regcache writing to the register
in all circumstances.

While here, also fix the configuration of I2S_RXDR and I2S_FIFOLR; these
are not writable so they do not suffer from the same problem as I2S_TXDR
but reading from I2S_RXDR does suffer from a similar problem.

Fixes: f0447f6cbb20 ("ASoC: rockchip: i2s: restore register during runtime_suspend/resume cycle", 2016-09-07)
Signed-off-by: John Keeping <john@metanate.com>
---
I'm not completely happy with marking I2S_TXDR as readable here, but I
can't see a better way to do this.  Neither "volatile" nor "precious"
seem to match exactly a writable FIFO register but this does at least
fix the bug and tegra30_ahub.c seems to take the same approach.

 sound/soc/rockchip/rockchip_i2s.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sound/soc/rockchip/rockchip_i2s.c b/sound/soc/rockchip/rockchip_i2s.c
index 908211e1d6fc..20855ed8e4b7 100644
--- a/sound/soc/rockchip/rockchip_i2s.c
+++ b/sound/soc/rockchip/rockchip_i2s.c
@@ -504,6 +504,7 @@ static bool rockchip_i2s_rd_reg(struct device *dev, unsigned int reg)
 	case I2S_INTCR:
 	case I2S_XFER:
 	case I2S_CLR:
+	case I2S_TXDR:
 	case I2S_RXDR:
 	case I2S_FIFOLR:
 	case I2S_INTSR:
@@ -518,6 +519,9 @@ static bool rockchip_i2s_volatile_reg(struct device *dev, unsigned int reg)
 	switch (reg) {
 	case I2S_INTSR:
 	case I2S_CLR:
+	case I2S_FIFOLR:
+	case I2S_TXDR:
+	case I2S_RXDR:
 		return true;
 	default:
 		return false;
@@ -527,6 +531,7 @@ static bool rockchip_i2s_volatile_reg(struct device *dev, unsigned int reg)
 static bool rockchip_i2s_precious_reg(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
+	case I2S_RXDR:
 	default:
 		return false;
 	}
-- 
2.15.1

Re: [PATCH] ASoC: rockchip: i2s: fix playback after runtime resume

[Mark Brown]

[-- Attachment #1.1: Type: text/plain, Size: 347 bytes --]

On Mon, Jan 08, 2018 at 12:23:01PM +0000, John Keeping wrote:

> @@ -527,6 +531,7 @@ static bool rockchip_i2s_volatile_reg(struct device *dev, unsigned int reg)
>  static bool rockchip_i2s_precious_reg(struct device *dev, unsigned int reg)
>  {
>  	switch (reg) {
> +	case I2S_RXDR:
>  	default:
>  		return false;
>  	}

This doesn't look right?

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: [PATCH] ASoC: rockchip: i2s: fix playback after runtime resume

[John Keeping]

On Mon, 8 Jan 2018 15:26:41 +0000, Mark Brown wrote:

> On Mon, Jan 08, 2018 at 12:23:01PM +0000, John Keeping wrote:
> 
> > @@ -527,6 +531,7 @@ static bool rockchip_i2s_volatile_reg(struct device *dev, unsigned int reg)
> >  static bool rockchip_i2s_precious_reg(struct device *dev, unsigned int reg)
> >  {
> >  	switch (reg) {
> > +	case I2S_RXDR:
> >  	default:
> >  		return false;
> >  	}  
> 
> This doesn't look right?

No, it's not, it should be "return true;" for I2S_RXDR.

[PATCH v2] ASoC: rockchip: i2s: fix playback after runtime resume

[John Keeping]

When restoring registers during runtime resume, we must not write to
I2S_TXDR which is the transmit FIFO as this queues up a sample to be
output and pushes all of the output channels down by one.

This can be demonstrated with the speaker-test utility:

	for i in a b c; do speaker-test -c 2 -s 1; done

which should play a test through the left speaker three times but if the
I2S hardware starts runtime suspended the first sample will be played
through the right speaker.

Fix this by marking I2S_TXDR as volatile (which also requires marking it
as readble, even though it technically isn't).  This seems to be the
most robust fix, the alternative of giving I2S_TXDR a default value is
more fragile since it does not prevent regcache writing to the register
in all circumstances.

While here, also fix the configuration of I2S_RXDR and I2S_FIFOLR; these
are not writable so they do not suffer from the same problem as I2S_TXDR
but reading from I2S_RXDR does suffer from a similar problem.

Fixes: f0447f6cbb20 ("ASoC: rockchip: i2s: restore register during runtime_suspend/resume cycle", 2016-09-07)
Signed-off-by: John Keeping <john@metanate.com>
---
v2 changes:
- Fix rockchip_i2s_precious_reg to return true for I2S_RXDR

 sound/soc/rockchip/rockchip_i2s.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sound/soc/rockchip/rockchip_i2s.c b/sound/soc/rockchip/rockchip_i2s.c
index 908211e1d6fc..eb27f6c24bf7 100644
--- a/sound/soc/rockchip/rockchip_i2s.c
+++ b/sound/soc/rockchip/rockchip_i2s.c
@@ -504,6 +504,7 @@ static bool rockchip_i2s_rd_reg(struct device *dev, unsigned int reg)
 	case I2S_INTCR:
 	case I2S_XFER:
 	case I2S_CLR:
+	case I2S_TXDR:
 	case I2S_RXDR:
 	case I2S_FIFOLR:
 	case I2S_INTSR:
@@ -518,6 +519,9 @@ static bool rockchip_i2s_volatile_reg(struct device *dev, unsigned int reg)
 	switch (reg) {
 	case I2S_INTSR:
 	case I2S_CLR:
+	case I2S_FIFOLR:
+	case I2S_TXDR:
+	case I2S_RXDR:
 		return true;
 	default:
 		return false;
@@ -527,6 +531,8 @@ static bool rockchip_i2s_volatile_reg(struct device *dev, unsigned int reg)
 static bool rockchip_i2s_precious_reg(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
+	case I2S_RXDR:
+		return true;
 	default:
 		return false;
 	}
-- 
2.15.1

Applied "ASoC: rockchip: i2s: fix playback after runtime resume" to the asoc tree

[Mark Brown]

The patch

   ASoC: rockchip: i2s: fix playback after runtime resume

has been applied to the asoc tree at

   https://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 c66234cfedfc3e6e3b62563a5f2c1562be09a35d Mon Sep 17 00:00:00 2001
From: John Keeping <john@metanate.com>
Date: Mon, 8 Jan 2018 16:01:04 +0000
Subject: [PATCH] ASoC: rockchip: i2s: fix playback after runtime resume

When restoring registers during runtime resume, we must not write to
I2S_TXDR which is the transmit FIFO as this queues up a sample to be
output and pushes all of the output channels down by one.

This can be demonstrated with the speaker-test utility:

	for i in a b c; do speaker-test -c 2 -s 1; done

which should play a test through the left speaker three times but if the
I2S hardware starts runtime suspended the first sample will be played
through the right speaker.

Fix this by marking I2S_TXDR as volatile (which also requires marking it
as readble, even though it technically isn't).  This seems to be the
most robust fix, the alternative of giving I2S_TXDR a default value is
more fragile since it does not prevent regcache writing to the register
in all circumstances.

While here, also fix the configuration of I2S_RXDR and I2S_FIFOLR; these
are not writable so they do not suffer from the same problem as I2S_TXDR
but reading from I2S_RXDR does suffer from a similar problem.

Fixes: f0447f6cbb20 ("ASoC: rockchip: i2s: restore register during runtime_suspend/resume cycle", 2016-09-07)
Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
---
 sound/soc/rockchip/rockchip_i2s.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sound/soc/rockchip/rockchip_i2s.c b/sound/soc/rockchip/rockchip_i2s.c
index 908211e1d6fc..eb27f6c24bf7 100644
--- a/sound/soc/rockchip/rockchip_i2s.c
+++ b/sound/soc/rockchip/rockchip_i2s.c
@@ -504,6 +504,7 @@ static bool rockchip_i2s_rd_reg(struct device *dev, unsigned int reg)
 	case I2S_INTCR:
 	case I2S_XFER:
 	case I2S_CLR:
+	case I2S_TXDR:
 	case I2S_RXDR:
 	case I2S_FIFOLR:
 	case I2S_INTSR:
@@ -518,6 +519,9 @@ static bool rockchip_i2s_volatile_reg(struct device *dev, unsigned int reg)
 	switch (reg) {
 	case I2S_INTSR:
 	case I2S_CLR:
+	case I2S_FIFOLR:
+	case I2S_TXDR:
+	case I2S_RXDR:
 		return true;
 	default:
 		return false;
@@ -527,6 +531,8 @@ static bool rockchip_i2s_volatile_reg(struct device *dev, unsigned int reg)
 static bool rockchip_i2s_precious_reg(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
+	case I2S_RXDR:
+		return true;
 	default:
 		return false;
 	}
-- 
2.15.1