PCI: imx6: Keep i.MX6 Root Port MSI/MSI-X Capabilities with iMSI-RX to work around...

PCI: imx6: Keep i.MX6 Root Port MSI/MSI-X Capabilities with iMSI-RX to work around hardware bug

On some NXP chipsets, disabling Root Port MSI/MSI-X Capabilities blocks
MSIs originating from Endpoints from reaching the iMSI-RX controller.

To address this hardware bug, commit 3a4e8302e72f ("PCI: imx6: Keep Root
Port MSI capability with iMSI-RX to work around hardware bug") preserves
Root Port MSI and MSI-X Capabilities on i.MX7D, i.MX8MM, and i.MX8MQ
when iMSI-RX is in use.

The same applies to i.MX6Q, i.MX6QP, and i.MX6SX, so preserve Root Port
MSI/MSI-X Capabilities there as well.

Note that preserving these Capabilities means Root Port-originated MSIs
such as AER and PME won't be received due to separate hardware limitations.
Users may need to use workarounds such as passing the 'pcie_pme=nomsi'
command-line parameter.

Fixes: f5cd8a929c825 ("PCI: dwc: Remove MSI/MSIX capability for Root Port if iMSI-RX is used as MSI controller")
Signed-off-by: Soeren Moch <smoch@web.de>
Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
Acked-by: Richard Zhu <hongxing.zhu@nxp.com>
Cc: stable@vger.kernel.org # 7.0+
Link: https://patch.msgid.link/20260717033203.2965045-1-hongxing.zhu@oss.nxp.com