How to enable SAI MCLK on iMX8MP?

[ensc]

What is required to output a clock e.g. on the `SAI2_MCLK` pin?

With iMX8MM, the clock started immediately after iomux have been configured.  E.g. in barebox bootloader I see the signal after

mw 0x303301c8 0

But on iMX8MP the signal stays static

mw 0x303a00d8 32    ## power up audio block
mw 0x303301b4 0     ## ALT0_AUDIOMIX_SAI2_MCLK

and can be toggled by changing pull up/down settings

mw 0x30330414 0x140     ## signal becomes high
mw 0x30330414 0x100     ## signal becomes low

Clocks are enabled, audio_blk_ctrl controller is having power-on settings and I enabled MOE in SAI MCTL:

 md 0x30384650  
30384650: 00000003 00000003 00000003 00000003                ................

:/ md 0x30e20000+8  
30e20000: ff777777 0000003f                                  www.?...

:/ md 0x30e20300+0x20
30e20300: 00000000 00000000 00000000 00000000                ................
30e20310: 00000000 00000000 00000000 00000000                ................

:/ md 0x30c20100          
30c20100: 80000000 00000000 xxxxxxxx xxxxxxxx                ................

What has to be configured else to output the MCLK signal?  I require it for using an SGTL5000 which needs MCLK for its i2c communication.

[Dhruvit]

Hi @ensc,

I have sent the additional details over email.

Thank you.

Best Regards,
Dhruvit.

[VoVan]

Can you see a solution to this problem? I have the same situation, the sgtl5000 works fine on the imx8mm board, since a normal clock is generated (MCLK - SAI3), but on the imx8mp board the clock does not work, as a result, there is no i2c device.

[ensc]

`FSL_SAI_MCTL_MCLK_EN` + `FSL_SAI_CSR_TERE` must be enabled to generate the clock.

I solved it by making SAI a clock provider and enable MCLK in sgtl5000 when needed.

- https://git.data-modul.com/i.mx8mm-std-mirror/components/kernel/-/commit/6dc48366bd8ce5778183ac0d5ed...

- https://git.data-modul.com/i.mx8mm-std-mirror/components/kernel/-/commit/9521345a094391fcab628aedcf7...

- https://git.data-modul.com/i.mx8mm-std-mirror/components/kernel/-/commit/dae9f931fb1472a410383cd2570...

- https://git.data-modul.com/i.mx8mm-std-mirror/components/kernel/-/commit/49e16c26682b54bff23ffce4ec4...

- https://git.data-modul.com/i.mx8mm-std-mirror/meta-dmo-imx8/-/blob/ac485fc6d075520aa0f27c6a54865a2b0...

It is racy like hell but works for now.  Future hardware will probably replace the SGTL5000

[Eddy1]

Hi:

Can your sgtl5000 work properly? Can you provide your device tree configuration? Currently, I followed your patch, but there is still no mclk output.

[VoVan]

Thanks, i'll try add this patches

[Dhruvit]

Hi @ensc,

I think there is no dependency of MCLK on I2C to work.

Could you please confirm at your end if there is something that you are missing related to any pins/GPIOs or SGTL5000?

Best Regards,
Dhruvit.

[ensc]

I think there is no dependency of MCLK on I2C to work.

MCLK is required; see Table 7 "Dynamic Electrical Characteristics", note 1

The SGTL5000 has an internal reset that is deasserted 8 SYS_MCLK cycles after all power rails have been brought up. After this time, communication can start.

and figure 4 "Power Up Timing"

But this question is about the iMX8MP;  I want to know how to generate SAI MCLK there.

[Dhruvit]

Hi @ensc,

Could you please try playing/recording something first to make SAI work?

For example, with default i.MX8MP evk, when I use the wm8960 for playback, SAI3 will be used, then I can read the register like,

ot@imx8mpevk:~# /unit_tests/memtool 30e20000 1
E
Reading 0x1 count starting at address 0x30E20000

0x30E20000:  04000300

Best Regards,
Dhruvit.

[ensc]

Could you please try playing/recording something first to make SAI work?

The problem is, that I can not play or record anything because I can not initialize the SGTL5000 due to the missing SAI_MCLK.

With iMX8MM on a similar hardware, this clock was easy to generate just by setting iomux.  This does not work anymore with iMX8MP.

What have I to do for generating SAI_MCLK?

For example, with default i.MX8MP evk, when I use the wm8960 for playback

I do not know the wm8960; perhaps its I2C works without the global mclk.

[edwardtyrrell]

Hi @ensc 

Have you resolved your issues?