How to tweak PCIE signal using IOMUXC_GPR8 register ?

[peteramond]

Hi All,

My custom hardware is based on iMX6Q processor and design most similar to nitrogen6_max and I'm using nitogen6_max uboot and dtbs.

Attached document says the parameters of PCIe_PHY can be adjusted by changing the IOMUXC_GPR8 register settings to get the test passed.

1) Where can I find above 0x20e0020 register in uboot ? Do I need to add that line to uboot ?

2) What values should I change to tweak PCIE signal ? When I go through nitrogen6_max uboot I can see following lines in two files. So what values should I change to tweak PCIE signal ?

File path >> arch/arm/include/asm/arch-mx6/iomux.h

File path >> drivers/pci/pcie_imx.c

3) Can you give me an example how to tweak PCIE signals using GPR8 register ?

Regards,

Peter.

[igorpadykov]

Hi Peter

>Where can I find above 0x20e0020 register in uboot ? Do I need to add that line to uboot ?

memtool is used in linux while in uboot one can use "mm" - memory modify comands
http://www.denx.de/wiki/publish/DULG/to-delete/UBootCmdGroupMemory.html 

>2) What values should I change to tweak PCIE signal ?

Values should be adjusted based on results measurements using
software SigTest Version 3.1.60 (sect.1.4 Analysis software AN4784) and
below documents (described in AN4784 sect.1.5 Additional information):

—  PCI Express® Architecture PHY Test Specification, rev. 2.0. (PCI-SIG: 2008, pcisig.com .
—  document #CLB_USAGE_DOC_Rev_1_4_DSA72000b, PCI Express 2.0 CEM System
Signal Quality and Reference Clock Jitter Test Methodology using Tektronix
MSO/DPO/DSA72004 (20GHz), MSO/DPO/DSA71604 (16GHz) and MSO/DPO/DSA71254
(12.5GHz) Real Time Oscilloscopes, rev. 1.4 (PCI-SIG, 2011; register at pcisig.com to
download this document).

>3) Can you give me an example how to tweak PCIE signals using GPR8 register ?

NXP can help customers with certification using Professional Services :
NXP Professional Services|NXP 

Best regards
igor
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