Re: [PATCH v2] PCI: imx6: Keep Root Port MSI capability also for i.MX6Q
From: Soeren Moch
Date: Fri Jul 17 2026 - 03:54:51 EST
On 17.07.26 00:27, Bjorn Helgaas wrote:
On Thu, Jul 16, 2026 at 11:40:54PM +0200, Soeren Moch wrote:Your proposed new patch subject and commit message is totally fine for me.
On the NXP i.MX6Q chipset MSIs from the endpoints won't be received byI'd like to align the subject a little more with 3a4e8302e72f and
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.
avoid repeating the ".. from reaching when the Root Port MSI ..." part
of the commit log, which seems to be missing a word. So I propose the
following (if you think it's accurate):
Thanks,
Soeren
PCI: imx6: Keep i.MX6Q Root Port MSI capability 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, 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, 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.
Also, we need to resolve the Sashiko question about whether IMX6QP and
IMX6SX also need this. NXP folks, can you verify?
Fixes: f5cd8a929c825 ("PCI: dwc: Remove MSI/MSIX capability for Root Port if iMSI-RX is used as MSI controller")
Cc: <stable@xxxxxxxxxxxxxxx> # 7.0+
Signed-off-by: Soeren Moch <smoch@xxxxxx>
Acked-by: Richard Zhu <hongxing.zhu@xxxxxxx>
Reviewed-by: Frank Li <Frank.Li@xxxxxxx>
Reviewed-by: Manivannan Sadhasivam <mani@xxxxxxxxxx>
---
Cc: Manivannan Sadhasivam <mani@xxxxxxxxxx>
Cc: Richard Zhu <hongxing.zhu@xxxxxxx>
Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Frank Li <Frank.Li@xxxxxxx>
Cc: Fabio Estevam <festevam@xxxxxxxxx>
Cc: linux-pci@xxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: imx@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
This patch is similar to
3a4e8302e72f ("PCI: imx6: Keep Root Port MSI capability with iMSI-RX to work around hardware bug")
Tested on a tbs2910 board [1]
[1] arch/arm/boot/dts/nxp/imx/imx6q-tbs2910.dts
changes in v2:
- collect a-b and r-b tags
- use correct fixes tag (Manivannan)
(reference commit that introduced the bug, not the incomplete fix)
Since this is a fix for a regression in linux-7.0+, can this still be merged for 7.2-rcS ?
---
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 98e1db751132..8130cf93c2bb 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,
--
2.43.0