Re: [PATCH] PCI: imx6: Keep Root Port MSI capability also for i.MX6Q

[Frank Li <Frank.li@nxp.com>]

On Mon, Apr 27, 2026 at 01:58:04PM +0200, Soeren Moch wrote:
> Also on the NXP i.MX6Q chipset MSIs from the endpoints won't be received by
> the iMSI-RX MSI controller if the Root Port MSI capability is disabled.
>
> Even though the Root Port MSIs won't be received by the iMSI-RX controller
> due to design, this chipset has some weird hardware bug that prevents
> the endpoint MSIs from reaching when the Root Port MSI capability is
> disabled.
>
> Hence, always keep the Root Port MSI capability for this chipset.
>
> Note that by keeping Root Port MSI capability, Root Port MSIs such as AER,
> PME and others won't be received by default. So users need to use
> workarounds such as passing 'pcie_pme=nomsi' cmdline param.
>
> Fixes: 3a4e8302e72f ("PCI: imx6: Keep Root Port MSI capability with iMSI-RX to work around hardware bug")
> Cc: <stable@vger.kernel.org> # 7.0.x
> Signed-off-by: Soeren Moch <smoch@web.de>

Reviewed-by: Frank Li <Frank.Li@nxp.com>

> ---
> Cc: Manivannan Sadhasivam <mani@kernel.org>
> Cc: Richard Zhu <hongxing.zhu@nxp.com>
> Cc: Lucas Stach <l.stach@pengutronix.de>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Frank Li <Frank.Li@nxp.com>
> Cc: Fabio Estevam <festevam@gmail.com>
> Cc: linux-pci@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: imx@lists.linux.dev
> Cc: linux-kernel@vger.kernel.org
>
> Tested on a tbs2910 board [1]
> [1] arch/arm/boot/dts/nxp/imx/imx6q-tbs2910.dts
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 6d6a1688e7eb..3d461bdef967 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -1865,7 +1865,8 @@ static const struct imx_pcie_drvdata drvdata[] = {
>  		.flags = IMX_PCIE_FLAG_IMX_PHY |
>  			 IMX_PCIE_FLAG_SPEED_CHANGE_WORKAROUND |
>  			 IMX_PCIE_FLAG_BROKEN_SUSPEND |
> -			 IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
> +			 IMX_PCIE_FLAG_SUPPORTS_SUSPEND |
> +			 IMX_PCIE_FLAG_KEEP_MSI_CAP,
>  		.dbi_length = 0x200,
>  		.gpr = "fsl,imx6q-iomuxc-gpr",
>  		.ltssm_off = IOMUXC_GPR12,
> --
> 2.43.0
>