* RE: [PATCH v2] PCI: imx6: Keep Root Port MSI capability also for i.MX6Q
2026-07-16 22:27 ` Bjorn Helgaas
@ 2026-07-17 2:48 ` Hongxing Zhu
2026-07-17 7:54 ` Soeren Moch
1 sibling, 0 replies; 4+ messages in thread
From: Hongxing Zhu @ 2026-07-17 2:48 UTC (permalink / raw)
To: Bjorn Helgaas, Soeren Moch
Cc: Bjorn Helgaas, stable@vger.kernel.org, Frank Li,
Manivannan Sadhasivam, Lucas Stach, Fabio Estevam,
linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
imx@lists.linux.dev, linux-kernel@vger.kernel.org
> -----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
> >
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] PCI: imx6: Keep Root Port MSI capability also for i.MX6Q
2026-07-16 22:27 ` Bjorn Helgaas
2026-07-17 2:48 ` Hongxing Zhu
@ 2026-07-17 7:54 ` Soeren Moch
1 sibling, 0 replies; 4+ messages in thread
From: Soeren Moch @ 2026-07-17 7:54 UTC (permalink / raw)
To: Bjorn Helgaas
Cc: Bjorn Helgaas, stable, Richard Zhu, Frank Li,
Manivannan Sadhasivam, Lucas Stach, Fabio Estevam, linux-pci,
linux-arm-kernel, imx, linux-kernel
On 17.07.26 00:27, Bjorn Helgaas wrote:
> 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):
Your proposed new patch subject and commit message is totally fine for me.
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@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
>>
^ permalink raw reply [flat|nested] 4+ messages in thread