ASoC: davinci-mcasp: Add digital loopback mode

Add support for the digital loopback mode. Even serializers N
transmit to odd serializers N+1 that receive.

The above order must be set accordingly in the "serial-dir" DT
property, e.g.:

  serial-dir = <1 2 0 0>;  /* 0:INACTIVE, 1:TX, 2:RX */

Change-Id: I01a240b040497439b5781d0c2eb4023bf6562da0
Signed-off-by: Misael Lopez Cruz <misael.lopez@ti.com>

3 files changed, 17 insertions, 0 deletions

diff --git a/include/linux/platform_data/davinci_asp.h b/include/linux/platform_data/davinci_asp.h
index 416c1d2abe63..2227fa4359d8 100644
--- a/include/linux/platform_data/davinci_asp.h
+++ b/include/linux/platform_data/davinci_asp.h
@@ -86,6 +86,7 @@ struct snd_platform_data {
         u8 rxnumevt;
         u32 tx_dismod;
         u32 rx_dismod;
+        bool loopback;
 };
 
 enum {
diff --git a/sound/soc/davinci/davinci-mcasp.c b/sound/soc/davinci/davinci-mcasp.c
index b264e8b69855..169d8c73cd0b 100644
--- a/sound/soc/davinci/davinci-mcasp.c
+++ b/sound/soc/davinci/davinci-mcasp.c
@@ -975,6 +975,13 @@ static int davinci_hw_param(struct davinci_audio_dev *dev, int stream,
         mcasp_mod_bits(dev->base + DAVINCI_MCASP_RXFMCTL_REG,
                        FSRMOD(total_slots), FSRMOD(0x1FF));
 
+        if (dev->loopback) {
+                dev_info(dev->dev, "%s configured in loopback mode",
+                         stream ? "capture" : "playback");
+                mcasp_set_reg(dev->base + DAVINCI_MCASP_LBCTL_REG,
+                              LBEN | LBORD | LBGENMODE(1));
+        }
+
         return 0;
 }
 
@@ -1459,6 +1466,11 @@ static struct snd_platform_data *davinci_mcasp_set_pdata_from_of(
         if (ret >= 0)
                 pdata->sram_size_capture = val;
 
+        if (of_find_property(np, "ti,loopback", NULL))
+                pdata->loopback = true;
+        else
+                pdata->loopback = false;
+
         return  pdata;
 
 nodata:
@@ -1556,6 +1568,7 @@ static int davinci_mcasp_probe(struct platform_device *pdev)
         dev->rxnumevt = pdata->rxnumevt;
         dev->tx_dismod = pdata->tx_dismod;
         dev->rx_dismod = pdata->rx_dismod;
+        dev->loopback = pdata->loopback;
         dev->dev = &pdev->dev;
 
         davinci_mcasp_serializer_offset(dev);
diff --git a/sound/soc/davinci/davinci-mcasp.h b/sound/soc/davinci/davinci-mcasp.h
index 3dfceb45dedb..b4317d76655a 100644
--- a/sound/soc/davinci/davinci-mcasp.h
+++ b/sound/soc/davinci/davinci-mcasp.h
@@ -54,6 +54,9 @@ struct davinci_audio_dev {
         /* McASP port related */
         bool    dat_port;
 
+        /* Digital loopback */
+        bool    loopback;
+
         struct snd_pcm_substream *substreams[2];
 };