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TPS65217C USB Power path current limit question (software)

Alexander Zakharov
Intellectual 295 points

Other Parts Discussed in Thread: TPS65217

Hello,

We have a problem setting PPATH current limit for USB to 1.8A. While we do set desirable value (1.8A - 0x3F)  in u-boot, kernel boot overrides it to 1.3A (0x3E). I carefully scouted all associated sources in TI 3.14y kernel, but do not see anywhere place where this change takes place. Of course we can set it up in user land by simply issuing i2cset command, but desirable behavior is to keep 1.8A all a way without any changes, the same as been set by uboot.


Can anybody point me out to the place in sources where kernel sets this register?

Thanks in advance,

Alex

  • 0
    TI__Guru**** 161600 points
    Hi Alex,

    Kernel driver, where pmic registers are set is located in drivers/mfd/tps65217.c.
    Also you should have a look at tps65xxx.dtsi files (where xx is replaced with the exact pmic part name ending, in your case 217).

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    Intellectual 295 points

    Hello Yordan,

    Thnaks a lot for the prompt reply. I already checked both multiple times - there are no settings for PPATH register anywhere in driver or dtb files. I scouted all sources very carefully - it is not there. The only last place to look at would be AM335X firmware, but where do I find sources?

    Looking at your 3.14y repository (which was used to build the kernel), there is no place where PPATH register is addressed.

    If you see one (in case I missed something), can you point to exact file and procedure where these settings take place?

    Cheers,

    Alex

  • 0 in reply to Alexander Zakharov
    TI__Guru**** 161600 points

    Hi Alex,

    You're correct, PPATH is not set in these kernel sources.

    Alexander Zakharov said:
    he only last place to look at would be AM335X firmware, but where do I find sources?

     

    You need to confirm this with the guys from PMU (e2e.ti.com/.../200) forum, but I am not sure that TPS firmware sources are publicly available. 

    Best Regards, 

    Yordan

  • 0 in reply to Yordan Kovachev
    Intellectual 295 points

    Thanks a lot Yordan for confirming my suspicion. The firmware that I did refer to is AM335X firmware, not PMIC. When we do build Linux kernel for AM335X, we use "ready to go" am335x-pm-firmware.bin or am335x-pm-firmware.elf files in kernel firmware directory, and refer to it in kernel configuration file. PPATH setting is definitely takes place here, but why? This binary supposed to set very basic stuff, such as memory etc., why on earth someone would decide to set PPATH for USB? It does not make any sense to me. Where I can find sources of these firmware files? (it's AM335X firmware, not TPS).


    Cheers,

    Alex

  • 0 in reply to Alexander Zakharov
    Intellectual 295 points

    So, having all the information gathered so far, can anybody answer the question? Where PPATH register of TPS PMIC is modified in Linux TI kernel? To refresh things: TPS65217C PPATH register (offset 0x1) values that we set in u-boot are altered by kernel, but TI Linux sources that were used to build the kernel (3.14y) do not have any reference to such a functionality anywhere.

    Any suggestions where to look?