AM6442: MCU i2c peripheral access from Main domain

Abin Raj

Part Number: AM6442
Other Parts Discussed in Thread: SYSCONFIG

Hi, I am trying to access the MCU i2c peripherals from the Main domain on my TMDS64GPEVM. I am using the Linux processor sdk 7.3 and the updated device tree files from https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/tree/arch/arm64/boot/dts/ti?h=ti-linux-5.10.y .

I have generated the pinmux for these peripherals (mcu_i2c0 & mcu_i2c1) from the Sysconfig tool, but since the wakeup pinmuxing is not defined in the dts, I am not able to test it out. Additionally the AM65 dts example show wkup_pmx, wkup_i2c as well as mcu_i2c. I am not sure how to proceed with this.

After setting the status of mcu_i2c0 & mcu_i2c1 to "okay" in the dts, these peripherals are shown in the Linux with i2cdetect command, but I am not able to detect the slaves that i connect to the safety connector.

Could you share steps on how I can get the mcu_i2c to work in main domain ?

Any help is greatly appreciated

over 4 years ago

+1 Dominic Rath over 4 years ago

Mastermind 7540 points

You need to define the mcu pinmux (e.g. in k3-am64-mcu.dtsi), pretty much the same as the main pinmux but of course with a different address and length, and then add the MCU peripheral pins to your board level dts file under a reference to that new mcu pinmux.

You also need to make sure U-Boot leaves the MCU padconfig registers unlocked. By default they are all locked, but U-Boot contains code to unlock most of the MMR regions, including main padconfig, but not the MCU padconfig. Either here: https://git.ti.com/cgit/ti-u-boot/ti-u-boot/tree/arch/arm/mach-k3/am642_init.c?h=ti-u-boot-2020.01#n28 or by simply writing the unlock pattern to the kick register somewhere in your U-Boot boot script.

Regards,

Dominic

0 Abin Raj over 4 years ago in reply to Dominic Rath

Prodigy 160 points

Thanks for the replay Dominic Rath. I have added the pinmux for MCU domain.

Could you share an example or point me in the direction as to how to do it via the u-boot script ?

0 Dominic Rath over 4 years ago in reply to Abin Raj

Mastermind 7540 points

You could try this on the U-Boot cmdline:

mw.l 0x4085008 0x68ef3490; mw.l 0x408500c 0xd172bc5a;

Then boot your target without resetting. If that works together with your DTS changes, just put the mw.l commands in your boot script. U-Boot starts executing the bootcmd, from there it depends on the default scripts (which I don't know well enough) and your changes.

Regards,

Dominic

0 Abin Raj over 4 years ago in reply to Dominic Rath

Prodigy 160 points

Thanks Dominic Rath. With these changes in uboot, I was able to get both the mcu i2c's working from Linux. There are some occasional failures, which I am not sure why.

From the TRM, I could see that the its the address of the kick registers. Could you tell me how you have arrived at the write values ?

0 Dominic Rath over 4 years ago in reply to Abin Raj

Mastermind 7540 points

Glad to hear you've got your MCU I2C working. I wont be able to help you with your occasional failures - maybe someone from TI can help, or you can figure it out on your own.

The write values for the kick/lock registers are in the TRM, too, have a look at TRM Rev. B, 5.1.2.3.1.2 Kick Protection Registers.

Regards,

Dominic

0 Abin Raj over 4 years ago in reply to Dominic Rath

Prodigy 160 points

Thanks again Dominic. Hopefully I will be able to figure it out or someone from TI might look into it and point me the in the direction.

I really appreciate the support provided even though you are not from TI

0 Nick Saulnier over 4 years ago in reply to Abin Raj

TI__Guru** 102350 points

Hello Abin,

FYI, we will add the MCU domain peripherals to the Linux device tree file in Linux Processor SDK 8.0, which should be available in a week or so. Those peripherals will be disabled by default since Linux assumes they are owned by the R5 cores, but you will be able to enable them by modifying the device tree.

Let me check whether you will still need to manually unlock the MCU padconfig registers in uboot for Linux SDK 8.0. Please ping the thread if I have not replied in a day or so.

Regards,

Nick

0 Thinh Nguyen over 4 years ago in reply to Nick Saulnier

Intellectual 825 points

Hello Nick,

In AM64x, MCU domain is defined to be isolated M4 core not R5F cores. The A53 and R5 are the main domain.

You said "Those peripherals will be disabled by default since Linux assumes they are owned by the R5 cores". I mean that the Linux SDK 8.0 will be add the k3-am64x-mcu.dtsi which will contain the R5F peripherals.

Regards,

Thinh

0 Abin Raj over 4 years ago in reply to Nick Saulnier

Prodigy 160 points

Any updates Nick Saulnier ?

0 Thinh Nguyen over 4 years ago in reply to Thinh Nguyen

Intellectual 825 points

Hello Nick,

When do you release PROCESSOR-SDK-LINUX-AM64X 8.0?

I am looking forward to it.

0 Abin Raj over 4 years ago in reply to Abin Raj

Prodigy 160 points

I have tested it in SDK 8.0. We still need to add the MCU pinmux, MCU peripheral pin mux and unlock the MCU padconfig registers in uboot to get it working in Linux

0 Thinh Nguyen over 4 years ago in reply to Abin Raj

Intellectual 825 points

Hello Abin Raj,

Please confirm me, MCU-I2C on Linux of SDK8.0 works well?

That is good reference for me.

Thank you so much

0 Abin Raj over 4 years ago in reply to Thinh Nguyen

Prodigy 160 points

Hi Thinh Nguyen, I was able to get the MCU I2Cs working with the above mentioned changes

0 Thinh Nguyen over 4 years ago in reply to Abin Raj

Intellectual 825 points

Thank you for your confirmation

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AM6442: MCU i2c peripheral access from Main domain