On Fri, Mar 27, 2026 at 08:12:29AM +0000, Hongxing Zhu wrote:

quoted

-----Original Message-----
From: Frank Li <frank.li@nxp.com>
Sent: 2026年3月19日 22:17
To: Hongxing Zhu <hongxing.zhu@nxp.com>
Cc: 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; stable@vger.kernel.org
Subject: Re: [PATCH v2] PCI: imx6: Don't remove MSI capability For
i.MX7D/i.MX8M

On Thu, Mar 19, 2026 at 05:18:23PM +0800, Richard Zhu wrote:

quoted

The MSI trigger mechanism for endpoint devices connected to i.MX7D,
i.MX8MM, and i.MX8MQ PCIe root complex ports depends on the MSI
capability register settings in the root complex. Removing the MSI
capability breaks MSI functionality for these endpoints.

Preserve the MSI capability for i.MX7D/i.MX8M PCIe root complex to
maintain MSI functionality.

Cc: stable@vger.kernel.org
Fixes: f5cd8a929c825 ("PCI: dwc: Remove MSI/MSIX capability for Root
Port if iMSI-RX is used as MSI controller")

I think it'd better add another varible to check in f5cd8a929c825 if
(pp->has_msi_ctrl && !pp->xxx_broken) or direct use IP version, which
already auto detected.

Previous patch have not consider this old version controller.

Hi Frank:
From what I've observed, this behavior seems tied to the specific controller
design. For example, neither the i.MX6Q nor the i.MX6SX exhibit this issue.

Yes, should rename has_msi_ctrl -> disable_msi_ctrl. Set it according to
difference condition, such as has_msi_ctrl or skip it for problem platform
such as i.MX8MM and i.MX8MQ.

Disable it and overwrite later will cause confuse.

The intention of commit f5cd8a929c825 is to remove the MSI capability from the
Root Complex (RC). From the author's perspective, this change should not
affect the  Endpoint's (EP) MSI functionality.

Yes, your patch fix  RC  mode?

Frank

I'm not sure do this check (pp->has_msi_ctrl && !pp->msi_broken) is proper or not.
Best Regards
Richard Zhu

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