[PATCH v4] PCI: imx6: Update MPLLB bandwidth to improve i.MX95 Gen3 PCIe stability

[Bjorn Helgaas]

On Fri, Jul 31, 2026 at 11:05:46AM +0800, hongxing.zhu at oss.nxp.com wrote:
> From: Richard Zhu <hongxing.zhu at nxp.com>
> 
> Bandwidth marginality was observed during i.MX95 Gen3 PCIe tests with
> the default MPLLB_BANDWIDTH value (120). This margin degradation worsens
> across voltage and temperature (VT) variations and different test
> matrices, potentially causing link stability issues.
> 
> Testing with MPLLB_BANDWIDTH value of 140 (0x8c) shows significant
> improvement in bandwidth margins across all VT conditions and test
> scenarios.
> 
> Implement PHY register write helper function and configure:
> - MPLLB_BW_OVRD_IN = 140 (0x8c) for improved bandwidth margin
> - MPLLB_BW_OVRD_EN to enable the override
> 
> This ensures robust PCIe Gen3 performance across all operating
> conditions.

Thanks for including the previous and new MPLLB_BANDWIDTH values.

I'm fine with the patch, but I think "bandwidth marginality" is
awkward wording because "marginality" doesn't seem to be commonly
used in this context.  Maybe something like:

  We observed poor bandwidth margins during ...  The margins worsened
  across ...