[alsa-devel] [PATCH v2] ASoC: fsl_ssi: Fix channel swap on playback start

[Fabio Estevam]

On Tue, Apr 4, 2017 at 8:38 AM, Fabio Estevam <festevam at gmail.com> wrote:

> I have the following SSI1 values (with the original 4.1-rc5 + pictrl patch):
>
> # cat /sys/kernel/debug/regmap/2028000.ssi/registers
> 00: 00000200
> 04: 00000000
> 10: 0000105b

Bits 6-5 (I2S_MODE) of register SCR are 10 of register SCR, which
means I2S slave mode.

The MX6 Reference Manual states:

"In I2S slave mode(SSI_SCR[6:5]=10), the following settings are
internally overridden by
the hardware:

Normal mode is selected (SSI_SCR[3]=0)
Tx frame sync length set to one-bit-long-frame (SSI_STCR[1]=1)
Rx frame sync length set to one-bit-long-frame (SSI_SRCR[1]=1)"

so I tried not to use the the one-bit-long-frame (since ENGcm06222 is
about bit length frame sync) override and changed it to I2S normal
mode instead:

--- a/sound/soc/fsl/fsl_ssi.c
+++ b/sound/soc/fsl/fsl_ssi.c
@@ -973,7 +973,7 @@ static int _fsl_ssi_set_dai_fmt(struct device *dev,
                        ssi_private->i2s_mode |= CCSR_SSI_SCR_I2S_MODE_MASTER;
                        break;
                case SND_SOC_DAIFMT_CBM_CFM:
-                       ssi_private->i2s_mode |= CCSR_SSI_SCR_I2S_MODE_SLAVE;
+                       ssi_private->i2s_mode |= CCSR_SSI_SCR_I2S_MODE_NORMAL;
                        break;
                default:
                        return -EINVAL;

and I do not get the channel swap anymore.

In what cases could we safely switch to I2S normal mode?

Thanks