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

[Soeren Moch <smoch@web.de>]

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