[v2,6/6] ASoC: sun4i-i2s: Add support for loopback

Commit Message

Code Kipper March 12, 2018, 3:57 p.m. UTC

From: Marcus Cooper <[e-mail]>

The DAI has a loopback register which can be set and therefore routes
the transmit fifo to receive fifo. This is useful for testing the block
without the need for any external hardware.

Signed-off-by: Marcus Cooper <[e-mail]>
---
 Documentation/devicetree/bindings/sound/sun4i-i2s.txt |  3 +++
 sound/soc/sunxi/sun4i-i2s.c                           | 11 +++++++++++
 2 files changed, 14 insertions(+)

Comments

Christopher Obbard March 13, 2018, 1:39 p.m. UTC | #1

Hi Mark,

>
>> +- loopback:  if this property is present then the dai is configured in
>> +             loopback mode where the output fifo is redirected to the input
>> +             fifo.
>
> This really doesn't seem like something that ought to go into the DT
> and hence ABI given that there's obviously no reason to use this in
> production.  Just make it be a #define in the code or something.

It would be nice to have this as an optional devicetree property so
when testing JACK latency etc I don't have to manually re-compile a
kernel...

Maxime Ripard March 13, 2018, 2:03 p.m. UTC | #2

On Tue, Mar 13, 2018 at 01:39:44PM +0000, Chris Obbard wrote:
> >> +- loopback:  if this property is present then the dai is configured in
> >> +             loopback mode where the output fifo is redirected to the input
> >> +             fifo.
> >
> > This really doesn't seem like something that ought to go into the DT
> > and hence ABI given that there's obviously no reason to use this in
> > production.  Just make it be a #define in the code or something.
> 
> It would be nice to have this as an optional devicetree property so
> when testing JACK latency etc I don't have to manually re-compile a
> kernel...

Another one might also argue that having to recompile the DT and
reflash the whole firmware or EEPROM is overkill for just testing JACK
latency.

Can't we create a module parameter for it?

Maxime

Patch

diff --git a/Documentation/devicetree/bindings/sound/sun4i-i2s.txt b/Documentation/devicetree/bindings/sound/sun4i-i2s.txt
index 3f966ac61b9e..325e3d4571f1 100644
--- a/Documentation/devicetree/bindings/sound/sun4i-i2s.txt
+++ b/Documentation/devicetree/bindings/sound/sun4i-i2s.txt
@@ -32,6 +32,9 @@  Optional properties:
 - allwinner,slot-width-override:if this property is present then the dai is
 				configured to extend the slot width to the
 				value specified. Min 8, Max 32.
+- loopback:	if this property is present then the dai is configured in
+		loopback mode where the output fifo is redirected to the input
+		fifo.
 
 - allwinner,playback-channels:  if this property is present then the number
 				of available channels is extended and the
diff --git a/sound/soc/sunxi/sun4i-i2s.c b/sound/soc/sunxi/sun4i-i2s.c
index 7cf4dfe440de..a3c33814d33e 100644
--- a/sound/soc/sunxi/sun4i-i2s.c
+++ b/sound/soc/sunxi/sun4i-i2s.c
@@ -31,6 +31,7 @@ 
 #define SUN4I_I2S_CTRL_MODE_MASK		BIT(5)
 #define SUN4I_I2S_CTRL_MODE_SLAVE			(1 << 5)
 #define SUN4I_I2S_CTRL_MODE_MASTER			(0 << 5)
+#define SUN4I_I2S_CTRL_LOOP			BIT(3)
 #define SUN4I_I2S_CTRL_TX_EN			BIT(2)
 #define SUN4I_I2S_CTRL_RX_EN			BIT(1)
 #define SUN4I_I2S_CTRL_GL_EN			BIT(0)
@@ -195,6 +196,8 @@  struct sun4i_i2s {
 
 	const struct sun4i_i2s_quirks	*variant;
 
+	bool loopback;
+
 	unsigned int	slot_width;
 };
 
@@ -639,6 +642,11 @@  static void sun4i_i2s_start_capture(struct sun4i_i2s *i2s)
 	regmap_update_bits(i2s->regmap, SUN4I_I2S_DMA_INT_CTRL_REG,
 			   SUN4I_I2S_DMA_INT_CTRL_RX_DRQ_EN,
 			   SUN4I_I2S_DMA_INT_CTRL_RX_DRQ_EN);
+
+	/* Debugging without codec */
+	if (i2s->loopback)
+		regmap_update_bits(i2s->regmap, SUN4I_I2S_CTRL_REG,
+				   SUN4I_I2S_CTRL_LOOP, SUN4I_I2S_CTRL_LOOP);
 }
 
 static void sun4i_i2s_start_playback(struct sun4i_i2s *i2s)
@@ -1204,6 +1212,9 @@  static int sun4i_i2s_probe(struct platform_device *pdev)
 			soc_dai->playback.channels_max = val;
 	}
 
+	if (of_property_read_bool(pdev->dev.of_node, "loopback"))
+		i2s->loopback = true;
+
 	pm_runtime_enable(&pdev->dev);
 	if (!pm_runtime_enabled(&pdev->dev)) {
 		ret = sun4i_i2s_runtime_resume(&pdev->dev);