[RESEND] drm/i2c: tda998x: Reset the I2S_FORMAT (Page0, Reg 0xfc) to it's default

[Peter Ujfalusi]

Hi Russell,

On 22/02/2019 16.35, Russell King - ARM Linux admin wrote:
> On Fri, Feb 22, 2019 at 03:47:14PM +0200, Peter Ujfalusi wrote:
>> Hi,
>>
>> the original version was sent 14.04.2018:
>> https://patchwork.kernel.org/patch/10344403/
>>
>> Changes since then:
>> - rebased on currentl drm/next
>>
>> The reset value of the register is 0, the soft reset does not reset this
>> register and if other kernel changed this the audio is going to be
>> distorted.
>>
>> It was observed when - accidentally - booted the kernel from eMMC on BBB
>> which is 3.8.13-bone79 and it sets this register to 0x0a. After reboot and
>> tda998x_reset() it remains 0x0a.
> 
> Have you checked whether the input I2S stream is Philips or Left
> Justified?  This is controlled by the LSB two bits.

The am335x-boneblack-common.dtsi configures the link to i2s, which
corresponds to Philips format (the default

> 
> It appears that 3.8.13-bone79 configures the TDA998x for left-
> justified, whereas re-setting these two bits to zero will configure
> it for Philips.

The chip reset value for the register is 0 and software reset will not
reset it if it was modified.

> Bits 3:2 control the data size, but I have no information what their
> values correspond to.

I can not find the register descriptions, can not tell what are the bits
in there.

> Can we nail down what is required for BBB and what it doesn't care
> about.

atm the REG_I2S_FORMAT register needs to be reset to 0.

> and I think we should implement at least setting the I2S
> register format from the hdmi_codec_daifmt data.

Yes, that needs to be done for sure, but without data sheet with
register descriptions I would not attempt to do that.

> It would also be good to know what Fs value(s) BBB uses, and what
> sample sizes you have tested.

On BBB McASP is the clock master and as I recall I have tested 44.1, 48
KHz at least with 16 and 24 bits.

>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi at ti.com>
>> ---
>>  drivers/gpu/drm/i2c/tda998x_drv.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
>> index 7f34601bb515..72f93802d209 100644
>> --- a/drivers/gpu/drm/i2c/tda998x_drv.c
>> +++ b/drivers/gpu/drm/i2c/tda998x_drv.c
>> @@ -722,6 +722,9 @@ tda998x_reset(struct tda998x_priv *priv)
>>  
>>  	/* Write the default value MUX register */
>>  	reg_write(priv, REG_MUX_VP_VIP_OUT, 0x24);
>> +
>> +	/* Write the default to I2S_FORMAT register */
>> +	reg_write(priv, REG_I2S_FORMAT,   0x00);
>>  }
>>  
>>  /*
>> -- 
>> Peter
>>
>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>>
>>
> 

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki