On Fri, Jan 09, 2026 at 02:10:07AM +0000, Hongxing Zhu wrote:

quoted

-----Original Message-----
From: Bjorn Helgaas <helgaas@kernel.org>
Sent: 2026年1月9日 5:50
To: Hongxing Zhu <hongxing.zhu@nxp.com>
Cc: Frank Li <frank.li@nxp.com>; l.stach@pengutronix.de;
lpieralisi@kernel.org; kwilczynski@kernel.org; mani@kernel.org;
robh@kernel.org; krzk+dt@kernel.org; conor+dt@kernel.org;
bhelgaas@google.com; shawnguo@kernel.org; s.hauer@pengutronix.de;
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linux-arm-kernel@lists.infradead.org; devicetree@vger.kernel.org;
imx@lists.linux.dev; linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 08/11] PCI: dwc: Invoke post_init in
dw_pcie_resume_noirq()

On Wed, Oct 15, 2025 at 11:04:25AM +0800, Richard Zhu wrote:

quoted

If the ops has post_init callback, invoke it in dw_pcie_resume_noirq().

I'm trying to write the merge commit log for this branch, and I don't quite
understand this.

The effect is to apply the GEN3_ZRXDC_NONCOMPL workaround for the
ERR051586 erratum, and Mani added the hint that this enables REFCLK
during resume.  But it seems weird that we apply a REFCLK workaround
after the link is already up.

During probe, .post_init() is run after pci_host_probe(), so we apply the
workaround after enumerating all the devices, which means REFCLK must
already be valid and the link is already up.

Is "enabling REFCLK" actually what imx_pcie_host_post_init() does?

The codes are used to clean up the CLKREQ# override active low
configurations after link is up and the CLKREQ# is drove to low by
remote endpoint device at this point(support-clkreq is TRUE).

It paves the way to support the CLKREQ# toggling mandatory required
by L1SS.

quoted

Could the workaround be done in imx_pcie_host_init() before the
link is brought up?  If it could, it looks like we wouldn't need
imx_pcie_host_post_init() at all.

Two actions are done in imx_pcie_post_init().

One is to apply the workaround of ERR051586 by commit 744a1c20ce93
("PCI: imx6: Add workaround for errata ERR051586"). It should be
applied after link is up.

The other one is to clean up the CLKREQ# override active low
configurations previous set in imx_pcie_host_init().

Right.  I'm not asking about the CLKREQ# part.  I'm asking about the
IMX_PCIE_FLAG_8GT_ECN_ERR051586 part.

The current commit log for this patch is this:

  Some SoCs like i.MX95 require enabling REFCLK after resuming from suspend
  in their post_init callback. So invoke the callback at the end of
  dw_pcie_resume_noirq() if available.

When .post_init() is called, the link is already up and PCIe devices
have already been enumerated.  I think REFCLK is required for the link
to come up, so it doesn't sound right to me that .post_init() would be
*enabling* REFCLK.

quoted

For now, I put this in the merge commit log:

  - Apply i.MX95 ERR051586 erratum workaround for REFCLK issue during
    resume (Richard Zhu)