-----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;
kernel@pengutronix.de; festevam@gmail.com; linux-pci@vger.kernel.org;
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.

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().

Hope this can resolve your confusions.

Best Regards
Richard Zhu

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

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

quoted

---
 drivers/pci/controller/dwc/pcie-designware-host.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c

b/drivers/pci/controller/dwc/pcie-designware-host.c
index 20c9333bcb1c4..2b59e7d2e6179 100644

--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c

@@ -1199,6 +1199,9 @@ int dw_pcie_resume_noirq(struct dw_pcie *pci)
 	if (ret)
 		return ret;

+	if (pci->pp.ops->post_init)
+		pci->pp.ops->post_init(&pci->pp);
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(dw_pcie_resume_noirq);
--

2.37.1