• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 101 subscribers
  • Views 633 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

AM6548: CPU frequency

AM6548: OPP support

Daisuke Maeda
Guru 20375 points

Part Number: AM6548

Nick Saulnier said:

In a later SDK, we will add support to select the operating point (OPP) at boot time through the device tree (800 MHz, 1GHz and 1.1 GHz). I cannot promise a timeline right now, but it seems likely to be in the October SDK release or the December SDK release.

The latest PSDK v06.02.00.81 does not seem to support the OPP changes.

Is the plan for a later PSDK to support the OPP changes at boot or runtime? If so, when is it?

Best regards,

Daisuke

  • 0
    TI__Guru** 108950 points

    Hello Daisuke,

    let me dig into this. If I have not replied by next week, feel free to send me a ping.

    Regards,

    Nick

  • 0 in reply to Nick Saulnier
    TI__Guru** 108950 points

    Hello Daisuke,

    There is not currently a plan to implement OPP changes during runtime on AM65x. However, you should be able to set the OPP at boot time in uboot.

    Note: As of Linux Processor SDK 6.2, the OPP voltage values in uboot should be manually updated to match the latest AM65x datasheet. Please see the post OPP Voltage vs Frequency for more information.

    I am still looking into how to set the OPP at boot time.

    Regards,

    Nick

  • 0 in reply to Nick Saulnier
    Guru 20375 points

    Hi Nick-san,

    Thank you for your reply.

    Nick Saulnier said:

    There is not currently a plan to implement OPP changes during runtime on AM65x. However, you should be able to set the OPP at boot time in uboot.

    The data sheet describes that a fixed OPP should be selected.

    AM654x, AM652x Sitara? Processors Silicon Revision 1.0 datasheet (Rev. I)
    http://www.ti.com/lit/ds/symlink/am6548.pdf
    5.5.1 Voltage and Core Clock Specifications (Page 125)
    "NOTE
     This device, when used in a production system, only supports one static OPP over the
     lifetime of the device. When designing a production system, a fixed OPP should be selected
     based on the maximum frequency required by the system. The corresponding OPP voltage
     must then be exclusively used by the device.
    "

    Is the above restriction only for the current silicon revision?

    Is there a plan that the above restriction is removed for a later silicon revision?

    Best regards,

    Daisuke

  • 0 in reply to Daisuke Maeda
    TI__Guru** 108950 points

    Hello Daisuke,

    I apologize for the delayed response.

    1) setting the OPP in uboot: I have attached some sample code to change the OPP frequency in uboot (e.g., from 800MHz to 1GHz or 1.1GHz). Note that as of SDK 6.2, the software team has only run tests at 800MHz. I do not expect to see software errors at higher core frequencies, but we have not tested to make sure. 

    4278.am654-Bump-up-MPU-speed-to-1GHz.zip

    2) To clarify the meaning of the note: The note says that the silicon can run at any of the three OPPs. However, once an OPP has been selected for a production part, the part should ONLY be run at that OPP for the lifetime of the part.

    I am checking on whether this note will apply to future silicon revisions of AM65x devices.

    Regards,

    Nick

  • 0 in reply to Nick Saulnier
    Guru 20375 points

    Hi Nick-san,

    Thank you for your cooperation.

    Best regards,

    Daisuke

  • 0 in reply to Daisuke Maeda
    TI__Guru** 108950 points

    Hello Daisuke,

    To clarify: The note specifically applies to OPP voltage. So silicon can run at any of the three OPPs. However, once an OPP has been selected for a production part, the part should ONLY be run at that OPP voltage for the lifetime of the part. If/when dynamic frequency scaling (DFS) is introduced, it will be ok to scale the frequency as long as the voltage is statically set.

    This applies to both silicon revisions of AM65x.

    Regards,

    Nick

  • 0 in reply to Nick Saulnier
    Guru 20375 points

    Hi Nick-san,

    Thank you for your information.

    Best regards,

    Daisuke