Re: [PATCH v2] PCI: imx6: Keep Root Port MSI capability also for i.MX6Q

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] The patch applies the IMX_PCIE_FLAG_KEEP_MSI_CAP workaround to IMX6Q but fails to apply it to IMX6QP and IMX6SX, leaving endpoint MSIs broken on those platforms.
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--- Patch [1]: [PATCH v2] PCI: imx6: Keep Root Port MSI capability also for i.MX6Q ---
commit c39e7347457d41f45ace38b5f670a9cded21c82b
Author: Soeren Moch <smoch@web.de>
PCI: imx6: Keep Root Port MSI capability also for i.MX6Q

This commit works around a hardware bug on the NXP i.MX6Q chipset where
endpoint MSIs are dropped if the Root Port MSI capability is disabled.
It achieves this by unconditionally applying the IMX_PCIE_FLAG_KEEP_MSI_CAP
flag to keep the Root Port MSI capability active.

> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 98e1db751132a..8130cf93c2bb4 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -1995,7 +1995,8 @@ 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,

[Severity: High]
This is a pre-existing issue, but should the IMX6QP and IMX6SX variants also
receive the IMX_PCIE_FLAG_KEEP_MSI_CAP workaround?

Looking at the drvdata definitions in this same file, the IMX6QP and IMX6SX
variants lack the IMX_PCIE_FLAG_KEEP_MSI_CAP flag:

        [IMX6SX] = {
                .variant = IMX6SX,
                .flags = IMX_PCIE_FLAG_IMX_PHY |
                         IMX_PCIE_FLAG_SPEED_CHANGE_WORKAROUND |
                         IMX_PCIE_FLAG_SKIP_L23_READY |
                         IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
                ...

        [IMX6QP] = {
                .variant = IMX6QP,
                .flags = IMX_PCIE_FLAG_IMX_PHY |
                         IMX_PCIE_FLAG_SPEED_CHANGE_WORKAROUND |
                         IMX_PCIE_FLAG_SKIP_L23_READY |
                         IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
                ...

Since they use the iMSI-RX controller and share the same DesignWare PCIe
integration as IMX6Q, dw_pcie_setup_rc() strips their Root Port MSI capability
unless the keep_rp_msi_en flag is set.

Does leaving this flag off cause IRQ timeouts and complete functional failure
of MSI-reliant PCIe devices on IMX6QP and IMX6SX platforms due to the same
hardware bug?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260716214054.47372-1-smoch@web.de?part=1