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

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

[Soeren Moch]

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

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

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

[sashiko-bot]

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.
--

--- 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

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

[Soeren Moch]

Resend as plain text.

On 17.07.26 00:01, Soeren Moch wrote:
On 16.07.26 23:51, sashiko-bot@kernel.org wrote:
> 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.
> --
>
> --- 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?
>
Unfortunately I have no access to IMX6QP and IMX6SX platforms. So I 
cannot judge if the same fix should be used for these platforms as well. 
If this fix is required for all platforms that are supported in this 
driver, why is this added as a special quirk? -- Soeren

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

[Bjorn Helgaas]

On Thu, Jul 16, 2026 at 11:40:54PM +0200, Soeren Moch wrote:
> 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.

I'd like to align the subject a little more with 3a4e8302e72f and
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):

  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@vger.kernel.org> # 7.0+
> Signed-off-by: Soeren Moch <smoch@web.de>
> Acked-by: Richard Zhu <hongxing.zhu@nxp.com>
> Reviewed-by: Frank Li <Frank.Li@nxp.com>
> Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
> ---
> 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
> 
> 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
> 

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

[Hongxing Zhu]

> -----Original Message-----
> From: Bjorn Helgaas <helgaas@kernel.org>
> Sent: Friday, July 17, 2026 6:27 AM
> To: Soeren Moch <smoch@web.de>
> Cc: Bjorn Helgaas <bhelgaas@google.com>; stable@vger.kernel.org; Hongxing
> Zhu <hongxing.zhu@nxp.com>; Frank Li <frank.li@nxp.com>; Manivannan
> Sadhasivam <mani@kernel.org>; Lucas Stach <l.stach@pengutronix.de>; Fabio
> Estevam <festevam@gmail.com>; linux-pci@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; imx@lists.linux.dev; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v2] PCI: imx6: Keep Root Port MSI capability also for i.MX6Q
> 
> On Thu, Jul 16, 2026 at 11:40:54PM +0200, Soeren Moch wrote:
> > 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.
> 
> I'd like to align the subject a little more with 3a4e8302e72f and 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):
> 
>   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?
Hi Bjorn:
Thank you for the reminder.

You are correct. I apologize for not covering these legacy platforms
initially. I have now verified that i.MX6QP and i.MX6SX PCIe controllers have
the same issue, so the fix should be applied to these platforms as well.

Should I send a separate patch for i.MX6QP and i.MX6SX, or would you prefer
that I extend this commit to cover all three variants in v3?

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