Re: [PATCH v3] PCI: imx6: Keep i.MX6Q Root Port MSI capability with iMSI-RX to work around hardware bug

[Soeren Moch]

On 17.07.26 05:32, hongxing.zhu@xxxxxxxxxxx wrote:
> From: Soeren Moch <smoch@xxxxxx>
>
> 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, commit 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, i.MX6QP and i.MX6SX. 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.
>
> 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>
> Signed-off-by: Richard Zhu <hongxing.zhu@xxxxxxx>
> Acked-by: Richard Zhu <hongxing.zhu@xxxxxxx>
> Reviewed-by: Frank Li <Frank.Li@xxxxxxx>
> Reviewed-by: Manivannan Sadhasivam <mani@xxxxxxxxxx>
> ---
> changes in v3:
> - Extend the fix to i.MX6QP and i.MX6SX variants as well.
> - Update the commit descriptions suggested by Bjorn.
Thanks Richard for checking 6QP and 6SX platforms and extending the fix 
for them.

Soeren
> 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)
> ---
>   drivers/pci/controller/dwc/pci-imx6.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 98e1db751132a..dba27eac6bff6 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,
> @@ -2011,7 +2012,8 @@ static const struct imx_pcie_drvdata drvdata[] = {
>   		.flags = IMX_PCIE_FLAG_IMX_PHY |
>   			 IMX_PCIE_FLAG_SPEED_CHANGE_WORKAROUND |
>   			 IMX_PCIE_FLAG_SKIP_L23_READY |
> -			 IMX_PCIE_FLAG_SUPPORTS_SUSPEND,
> +			 IMX_PCIE_FLAG_SUPPORTS_SUSPEND |
> +			 IMX_PCIE_FLAG_KEEP_MSI_CAP,
>   		.gpr = "fsl,imx6q-iomuxc-gpr",
>   		.ltssm_off = IOMUXC_GPR12,
>   		.ltssm_mask = IMX6Q_GPR12_PCIE_CTL_2,
> @@ -2026,7 +2028,8 @@ static const struct imx_pcie_drvdata drvdata[] = {
>   		.flags = IMX_PCIE_FLAG_IMX_PHY |
>   			 IMX_PCIE_FLAG_SPEED_CHANGE_WORKAROUND |
>   			 IMX_PCIE_FLAG_SKIP_L23_READY |
> -			 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,