ASoC: davinci-mcasp: Logic low for inactive output slots
The default state when serializers are in inactive slots is Hi-Z.
In some cases, there are no additional components driving the data
lines to a safe state so they might have noise.
While in inactive slots, the McASP AXR pins configured as outputs
can be driven low through the serializer pin drive mode setting
(DISMOD) to prevent such noise.
Signed-off-by: Misael Lopez Cruz <misael.lopez@ti.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/sound/soc/davinci/davinci-mcasp.c b/sound/soc/davinci/davinci-mcasp.c
index 56da8ce..68356f2c 100644
--- a/sound/soc/davinci/davinci-mcasp.c
+++ b/sound/soc/davinci/davinci-mcasp.c
@@ -686,6 +686,8 @@
if (mcasp->serial_dir[i] == TX_MODE &&
tx_ser < max_active_serializers) {
mcasp_set_bits(mcasp, DAVINCI_MCASP_PDIR_REG, AXR(i));
+ mcasp_mod_bits(mcasp, DAVINCI_MCASP_XRSRCTL_REG(i),
+ DISMOD_LOW, DISMOD_MASK);
tx_ser++;
} else if (mcasp->serial_dir[i] == RX_MODE &&
rx_ser < max_active_serializers) {
diff --git a/sound/soc/davinci/davinci-mcasp.h b/sound/soc/davinci/davinci-mcasp.h
index 79dc511..a3be108 100644
--- a/sound/soc/davinci/davinci-mcasp.h
+++ b/sound/soc/davinci/davinci-mcasp.h
@@ -215,7 +215,10 @@
* DAVINCI_MCASP_XRSRCTL_BASE_REG - Serializer Control Register Bits
*/
#define MODE(val) (val)
-#define DISMOD (val)(val<<2)
+#define DISMOD_3STATE (0x0)
+#define DISMOD_LOW (0x2 << 2)
+#define DISMOD_HIGH (0x3 << 2)
+#define DISMOD_MASK DISMOD_HIGH
#define TXSTATE BIT(4)
#define RXSTATE BIT(5)
#define SRMOD_MASK 3