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From: Bjorn Helgaas <helgaas@kernel.org>
To: hongxing.zhu@oss.nxp.com
Cc: frank.li@nxp.com, l.stach@pengutronix.de, lpieralisi@kernel.org,
	kwilczynski@kernel.org, mani@kernel.org, robh@kernel.org,
	bhelgaas@google.com, s.hauer@pengutronix.de,
	kernel@pengutronix.de, festevam@gmail.com,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	imx@lists.linux.dev, linux-kernel@vger.kernel.org,
	Richard Zhu <hongxing.zhu@nxp.com>
Subject: Re: [PATCH v4] PCI: imx6: Update MPLLB bandwidth to improve i.MX95 Gen3 PCIe stability
Date: Fri, 31 Jul 2026 11:02:58 -0500	[thread overview]
Message-ID: <20260731160258.GA1571469@bhelgaas> (raw)
In-Reply-To: <20260731030546.850457-1-hongxing.zhu@oss.nxp.com>

On Fri, Jul 31, 2026 at 11:05:46AM +0800, hongxing.zhu@oss.nxp.com wrote:
> From: Richard Zhu <hongxing.zhu@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 ...

  parent reply	other threads:[~2026-07-31 16:02 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-31  3:05 [PATCH v4] PCI: imx6: Update MPLLB bandwidth to improve i.MX95 Gen3 PCIe stability hongxing.zhu
2026-07-31  3:21 ` sashiko-bot
2026-07-31 16:02 ` Bjorn Helgaas [this message]
2026-08-03  2:54   ` Hongxing Zhu (OSS)

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