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

[Russell King - ARM Linux admin]

On Fri, Feb 22, 2019 at 05:20:15PM +0200, Peter Ujfalusi wrote:
> 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.

So I wonder why 3.8.13-bone79 configures it for left-justified.

> > 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.

Sorry, I wasn't clear enough... is the bus clocked at 32Fs for 16bit
samples and 64Fs for 24bit samples, or is it 64Fs for both?

> >> 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
> 

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