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

[Soeren Moch]

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 at vger.kernel.org> # 7.0.x
Signed-off-by: Soeren Moch <smoch at web.de>
---
Cc: Manivannan Sadhasivam <mani at kernel.org>
Cc: Richard Zhu <hongxing.zhu at nxp.com>
Cc: Lucas Stach <l.stach at pengutronix.de>
Cc: Bjorn Helgaas <bhelgaas at google.com>
Cc: Frank Li <Frank.Li at nxp.com>
Cc: Fabio Estevam <festevam at gmail.com>
Cc: linux-pci at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: imx at lists.linux.dev
Cc: linux-kernel at 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