[PATCH v2 1/5] ASoC: sh: rz-ssi: Drop calling rz_ssi_pio_recv() recursively

[PATCH v2 1/5] ASoC: sh: rz-ssi: Drop calling rz_ssi_pio_recv() recursively

[Lad Prabhakar]

Instead of recursively calling rz_ssi_pio_recv() use a loop instead
to read the samples from RX fifo.

Inspiration for this patch is to avoid recursion, as recursion is
unwelcome in kernel due to limited stack use. Also to add this driver
will later be used on RZ/A2 SoC's which runs with limited memory.

This also fixes an issue where the return value of rz_ssi_pio_recv()
was ignored when called recursively.

Fixes: 03e786bd4341 ("ASoC: sh: Add RZ/G2L SSIF-2 driver")
Reported-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
---
v1->v2
* Used a do while loop
* Fixed comments pointed by Cezary.
---
 sound/soc/sh/rz-ssi.c | 65 +++++++++++++++++++++----------------------
 1 file changed, 31 insertions(+), 34 deletions(-)

diff --git a/sound/soc/sh/rz-ssi.c b/sound/soc/sh/rz-ssi.c
index fa0cc08f70ec..637802117c6c 100644
--- a/sound/soc/sh/rz-ssi.c
+++ b/sound/soc/sh/rz-ssi.c
@@ -414,51 +414,48 @@ static int rz_ssi_pio_recv(struct rz_ssi_priv *ssi, struct rz_ssi_stream *strm)
 	u16 *buf;
 	int fifo_samples;
 	int frames_left;
-	int samples = 0;
+	int samples;
 	int i;
 
 	if (!rz_ssi_stream_is_valid(ssi, strm))
 		return -EINVAL;
 
 	runtime = substream->runtime;
-	/* frames left in this period */
-	frames_left = runtime->period_size - (strm->buffer_pos %
-					      runtime->period_size);
-	if (frames_left == 0)
-		frames_left = runtime->period_size;
 
-	/* Samples in RX FIFO */
-	fifo_samples = (rz_ssi_reg_readl(ssi, SSIFSR) >>
-			SSIFSR_RDC_SHIFT) & SSIFSR_RDC_MASK;
-
-	/* Only read full frames at a time */
-	while (frames_left && (fifo_samples >= runtime->channels)) {
-		samples += runtime->channels;
-		fifo_samples -= runtime->channels;
-		frames_left--;
-	}
-
-	/* not enough samples yet */
-	if (samples == 0)
-		return 0;
+	do {
+		/* frames left in this period */
+		frames_left = runtime->period_size -
+			      (strm->buffer_pos % runtime->period_size);
+		if (!frames_left)
+			frames_left = runtime->period_size;
+
+		/* Samples in RX FIFO */
+		fifo_samples = (rz_ssi_reg_readl(ssi, SSIFSR) >>
+				SSIFSR_RDC_SHIFT) & SSIFSR_RDC_MASK;
+
+		/* Only read full frames at a time */
+		samples = 0;
+		while (frames_left && (fifo_samples >= runtime->channels)) {
+			samples += runtime->channels;
+			fifo_samples -= runtime->channels;
+			frames_left--;
+		}
 
-	/* calculate new buffer index */
-	buf = (u16 *)(runtime->dma_area);
-	buf += strm->buffer_pos * runtime->channels;
+		/* not enough samples yet */
+		if (!samples)
+			break;
 
-	/* Note, only supports 16-bit samples */
-	for (i = 0; i < samples; i++)
-		*buf++ = (u16)(rz_ssi_reg_readl(ssi, SSIFRDR) >> 16);
+		/* calculate new buffer index */
+		buf = (u16 *)runtime->dma_area;
+		buf += strm->buffer_pos * runtime->channels;
 
-	rz_ssi_reg_mask_setl(ssi, SSIFSR, SSIFSR_RDF, 0);
-	rz_ssi_pointer_update(strm, samples / runtime->channels);
+		/* Note, only supports 16-bit samples */
+		for (i = 0; i < samples; i++)
+			*buf++ = (u16)(rz_ssi_reg_readl(ssi, SSIFRDR) >> 16);
 
-	/*
-	 * If we finished this period, but there are more samples in
-	 * the RX FIFO, call this function again
-	 */
-	if (frames_left == 0 && fifo_samples >= runtime->channels)
-		rz_ssi_pio_recv(ssi, strm);
+		rz_ssi_reg_mask_setl(ssi, SSIFSR, SSIFSR_RDF, 0);
+		rz_ssi_pointer_update(strm, samples / runtime->channels);
+	} while (!frames_left && fifo_samples >= runtime->channels);
 
 	return 0;
 }
-- 
2.17.1

Re: [PATCH v2 1/5] ASoC: sh: rz-ssi: Drop calling rz_ssi_pio_recv() recursively

[Cezary Rojewski]

On 2022-01-15 2:22 AM, Lad Prabhakar wrote:
> Instead of recursively calling rz_ssi_pio_recv() use a loop instead
> to read the samples from RX fifo.
> 
> Inspiration for this patch is to avoid recursion, as recursion is
> unwelcome in kernel due to limited stack use. Also to add this driver
> will later be used on RZ/A2 SoC's which runs with limited memory.
> 
> This also fixes an issue where the return value of rz_ssi_pio_recv()
> was ignored when called recursively.
> 
> Fixes: 03e786bd4341 ("ASoC: sh: Add RZ/G2L SSIF-2 driver")
> Reported-by: Pavel Machek <pavel@denx.de>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
> ---
> v1->v2
> * Used a do while loop
> * Fixed comments pointed by Cezary.

Apart from my previous suggestions which have already been addressed, I 
don't see any issues with the patch, so:

Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>


Regards,
Czarek

Re: [PATCH v2 1/5] ASoC: sh: rz-ssi: Drop calling rz_ssi_pio_recv() recursively

[Mark Brown]

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On Sat, Jan 15, 2022 at 01:22:59AM +0000, Lad Prabhakar wrote:
> Instead of recursively calling rz_ssi_pio_recv() use a loop instead
> to read the samples from RX fifo.

This doesn't apply against current code, please check and resend.

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[PATCH v2 2/5] ASoC: sh: rz-ssi: Make the data structures available before registering the handlers

[Lad Prabhakar]

Initialize the spinlock and make the data structures available before
registering the interrupt handlers.

Reported-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
---
v1->v2
* No change
---
 sound/soc/sh/rz-ssi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sound/soc/sh/rz-ssi.c b/sound/soc/sh/rz-ssi.c
index 637802117c6c..89428945d48b 100644
--- a/sound/soc/sh/rz-ssi.c
+++ b/sound/soc/sh/rz-ssi.c
@@ -972,6 +972,9 @@ static int rz_ssi_probe(struct platform_device *pdev)
 	ssi->playback.priv = ssi;
 	ssi->capture.priv = ssi;
 
+	spin_lock_init(&ssi->lock);
+	dev_set_drvdata(&pdev->dev, ssi);
+
 	/* Error Interrupt */
 	ssi->irq_int = platform_get_irq_byname(pdev, "int_req");
 	if (ssi->irq_int < 0)
@@ -1019,8 +1022,6 @@ static int rz_ssi_probe(struct platform_device *pdev)
 	pm_runtime_enable(&pdev->dev);
 	pm_runtime_resume_and_get(&pdev->dev);
 
-	spin_lock_init(&ssi->lock);
-	dev_set_drvdata(&pdev->dev, ssi);
 	ret = devm_snd_soc_register_component(&pdev->dev, &rz_ssi_soc_component,
 					      rz_ssi_soc_dai,
 					      ARRAY_SIZE(rz_ssi_soc_dai));
-- 
2.17.1

[PATCH v2 3/5] ASoC: sh: rz-ssi: Drop ssi parameter from rz_ssi_stream_init()

[Lad Prabhakar]

ssi parameter is unused in rz_ssi_stream_init() so just drop it.

While at it, change the return type of rz_ssi_stream_init() to void
instead of int.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
---
v1->v2
* No change
---
 sound/soc/sh/rz-ssi.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/sound/soc/sh/rz-ssi.c b/sound/soc/sh/rz-ssi.c
index 89428945d48b..50699e94772b 100644
--- a/sound/soc/sh/rz-ssi.c
+++ b/sound/soc/sh/rz-ssi.c
@@ -201,9 +201,8 @@ static int rz_ssi_stream_is_valid(struct rz_ssi_priv *ssi,
 	return ret;
 }
 
-static int rz_ssi_stream_init(struct rz_ssi_priv *ssi,
-			      struct rz_ssi_stream *strm,
-			      struct snd_pcm_substream *substream)
+static void rz_ssi_stream_init(struct rz_ssi_stream *strm,
+			       struct snd_pcm_substream *substream)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 
@@ -219,8 +218,6 @@ static int rz_ssi_stream_init(struct rz_ssi_priv *ssi,
 
 	/* fifo init */
 	strm->fifo_sample_size = SSI_FIFO_DEPTH;
-
-	return 0;
 }
 
 static void rz_ssi_stream_quit(struct rz_ssi_priv *ssi,
@@ -723,9 +720,7 @@ static int rz_ssi_dai_trigger(struct snd_pcm_substream *substream, int cmd,
 		rz_ssi_reg_mask_setl(ssi, SSIFCR, SSIFCR_SSIRST, 0);
 		udelay(5);
 
-		ret = rz_ssi_stream_init(ssi, strm, substream);
-		if (ret)
-			goto done;
+		rz_ssi_stream_init(strm, substream);
 
 		if (ssi->dma_rt) {
 			bool is_playback;
-- 
2.17.1

[PATCH v2 4/5] ASoC: sh: rz-ssi: Change return type of rz_ssi_stream_is_valid() to bool

[Lad Prabhakar]

rz_ssi_stream_is_valid() never returns an int, it returns the result of
a condition which is either true or false.

While at it, drop "!!" as the expression is boolean.

Reported-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
---
v1->v2
* No change
---
 sound/soc/sh/rz-ssi.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/sound/soc/sh/rz-ssi.c b/sound/soc/sh/rz-ssi.c
index 50699e94772b..2da43eecfb3e 100644
--- a/sound/soc/sh/rz-ssi.c
+++ b/sound/soc/sh/rz-ssi.c
@@ -188,14 +188,14 @@ static inline bool rz_ssi_is_dma_enabled(struct rz_ssi_priv *ssi)
 	return (ssi->playback.dma_ch && (ssi->dma_rt || ssi->capture.dma_ch));
 }
 
-static int rz_ssi_stream_is_valid(struct rz_ssi_priv *ssi,
-				  struct rz_ssi_stream *strm)
+static bool rz_ssi_stream_is_valid(struct rz_ssi_priv *ssi,
+				   struct rz_ssi_stream *strm)
 {
 	unsigned long flags;
-	int ret;
+	bool ret;
 
 	spin_lock_irqsave(&ssi->lock, flags);
-	ret = !!(strm->substream && strm->substream->runtime);
+	ret = strm->substream && strm->substream->runtime;
 	spin_unlock_irqrestore(&ssi->lock, flags);
 
 	return ret;
-- 
2.17.1

[PATCH v2 5/5] ASoC: sh: rz-ssi: Add rz_ssi_set_substream() helper function

[Lad Prabhakar]

A copy of substream pointer is stored in priv structure during
rz_ssi_dai_trigger() callback ie in SNDRV_PCM_TRIGGER_START case
and the pointer is assigned to NULL in case of SNDRV_PCM_TRIGGER_STOP.

The driver used the locks only in rz_ssi_stream_is_valid() and assigned
the local substream pointer to NULL in rz_ssi_dai_trigger() callback but
never locked it while making a local copy.

This patch adds the rz_ssi_set_substream() helper function to set the
substream pointer with locks acquired and replaces the instances of
setting the local substream pointer with the rz_ssi_set_substream()
function.

Reported-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
---
v1->v2
* Dropped rz_ssi_get_substream() helper.
---
 sound/soc/sh/rz-ssi.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/sound/soc/sh/rz-ssi.c b/sound/soc/sh/rz-ssi.c
index 2da43eecfb3e..07fdbcfa5b63 100644
--- a/sound/soc/sh/rz-ssi.c
+++ b/sound/soc/sh/rz-ssi.c
@@ -188,6 +188,17 @@ static inline bool rz_ssi_is_dma_enabled(struct rz_ssi_priv *ssi)
 	return (ssi->playback.dma_ch && (ssi->dma_rt || ssi->capture.dma_ch));
 }
 
+static void rz_ssi_set_substream(struct rz_ssi_stream *strm,
+				 struct snd_pcm_substream *substream)
+{
+	struct rz_ssi_priv *ssi = strm->priv;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ssi->lock, flags);
+	strm->substream = substream;
+	spin_unlock_irqrestore(&ssi->lock, flags);
+}
+
 static bool rz_ssi_stream_is_valid(struct rz_ssi_priv *ssi,
 				   struct rz_ssi_stream *strm)
 {
@@ -206,7 +217,7 @@ static void rz_ssi_stream_init(struct rz_ssi_stream *strm,
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 
-	strm->substream = substream;
+	rz_ssi_set_substream(strm, substream);
 	strm->sample_width = samples_to_bytes(runtime, 1);
 	strm->dma_buffer_pos = 0;
 	strm->period_counter = 0;
@@ -224,11 +235,8 @@ static void rz_ssi_stream_quit(struct rz_ssi_priv *ssi,
 			       struct rz_ssi_stream *strm)
 {
 	struct snd_soc_dai *dai = rz_ssi_get_dai(strm->substream);
-	unsigned long flags;
 
-	spin_lock_irqsave(&ssi->lock, flags);
-	strm->substream = NULL;
-	spin_unlock_irqrestore(&ssi->lock, flags);
+	rz_ssi_set_substream(strm, NULL);
 
 	if (strm->oerr_num > 0)
 		dev_info(dai->dev, "overrun = %d\n", strm->oerr_num);
-- 
2.17.1