IMX6 solo pci-express spread spectrum

[jewest]

Dear Forum members,

I am looking for the white paper how to set the pci-express spread spectrum for the IMX6solo.

For the i.MX 6Solo/6DualLite Applications Processor Reference Manual

Document Number: IMX6SDLRM
Rev. 5, I found that I need to modify the register described on 50.7.11 PCIE_PHY_SSC_OVRD_IN.

I need to modify https://github.com/boundarydevices/linux/blob/boundary-imx_3.0.35_4.1.0/arch/arm/mach-mx6/pcie.c

If I understand it correctly.

Best regards,

Jeffrey Westgeest

[art · Accepted solution]

Please refer to the Section "50.5.1.3 Spread Spectrum Clocking" of the IMX6SDLRM
Rev.5 document. It says the following.

"The PCIe2 PHY uses the PCIe reference clock which may or may not be spread. Since
the PCIe specification does not allow independently spread clocks, the ability of the PHY
to add a spread to a fixed frequency reference clock must be disabled."

So, the PCIe PHY spread spectrum clock feature is non-functional on the i.MX6Solo processor.

Best Regards,
Artur

[jewest]

In the document i.MX 6Solo/6DualLite Applications Processor Reference Manual, Rev. 5, 05/2020.

page 4464, there is a note: Must be set for PHASE writes to stick.

This is about bit 14 of the PCIE_PHY_SS_FREQ register.

With this phase does the manual mean PCIE_PHY_SS_PHASE?