Re: [PATCH 3/5] PCI: dwc: Remove MSI/MSIX capability if iMSI-RX is used as MSI controller

[Shawn Lin <shawn.lin@rock-chips.com>]

在 2025/11/28 星期五 17:57, Qiang Yu 写道:
> On Fri, Nov 21, 2025 at 12:04:09PM +0800, Shawn Lin wrote:
>> 在 2025/11/21 星期五 1:00, Manivannan Sadhasivam 写道:
>>> On Thu, Nov 20, 2025 at 10:06:03PM +0800, Shawn Lin wrote:
>>>> 在 2025/11/10 星期一 14:59, Qiang Yu 写道:
>>>>> Some platforms may not support ITS (Interrupt Translation Service) and
>>>>> MBI (Message Based Interrupt), or there are not enough available empty SPI
>>>>> lines for MBI, in which case the msi-map and msi-parent property will not
>>>>> be provided in device tree node. For those cases, the DWC PCIe driver
>>>>> defaults to using the iMSI-RX module as MSI controller. However, due to
>>>>> DWC IP design, iMSI-RX cannot generate MSI interrupts for Root Ports even
>>>>> when MSI is properly configured and supported as iMSI-RX will only monitor
>>>>> and intercept incoming MSI TLPs from PCIe link, but the memory write
>>>>> generated by Root Port are internal system bus transactions instead of
>>>>> PCIe TLPs, so they are ignored.
>>>>>
>>>>> This leads to interrupts such as PME, AER from the Root Port not received
>>>>
>>>> This's true which also stops Rockchip's dwc IP from working with AER
>>>> service. But my platform can't work with AER service even with ITS support.
>>>>
>>>>> on the host and the users have to resort to workarounds such as passing
>>>>> "pcie_pme=nomsi" cmdline parameter.
>>>>
>>>> ack.
>>>>
>>>>>
>>>>> To ensure reliable interrupt handling, remove MSI and MSI-X capabilities
>>>>> from Root Ports when using iMSI-RX as MSI controller, which is indicated
>>>>> by has_msi_ctrl == true. This forces a fallback to INTx interrupts,
>>>>> eliminating the need for manual kernel command line workarounds.
>>>>>
>>>>> With this behavior:
>>>>> - Platforms with ITS/MBI support use ITS/MBI MSI for interrupts from all
>>>>>      components.
>>>>> - Platforms without ITS/MBI support fall back to INTx for Root Ports and
>>>>>      use iMSI-RX for other PCI devices.
>>>>>
>>>>> Signed-off-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
>>>>> ---
>>>>>     drivers/pci/controller/dwc/pcie-designware-host.c | 10 ++++++++++
>>>>>     1 file changed, 10 insertions(+)
>>>>>
>>>>> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
>>>>> index 20c9333bcb1c4812e2fd96047a49944574df1e6f..3724aa7f9b356bfba33a6515e2c62a3170aef1e9 100644
>>>>> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
>>>>> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
>>>>> @@ -1083,6 +1083,16 @@ int dw_pcie_setup_rc(struct dw_pcie_rp *pp)
>>>>>     	dw_pcie_dbi_ro_wr_dis(pci);
>>>>> +	/*
>>>>> +	 * If iMSI-RX module is used as the MSI controller, remove MSI and
>>>>> +	 * MSI-X capabilities from PCIe Root Ports to ensure fallback to INTx
>>>>> +	 * interrupt handling.
>>>>> +	 */
>>>>> +	if (pp->has_msi_ctrl) {
>>>>
>>>> Isn't has_msi_ctrl means you have something like GIC-ITS
>>>> support instead of iMSI module? Am I missing anything?
>>>>
>>>
>>> It is the other way around. Presence of this flag means, iMSI-RX is used. But I
>>> think the driver should clear the CAPs irrespective of this flag.
>>
>> Thanks for correcting me. Yeap, how can I make such a mistake. :(
>>
>> Anyway, this patch works for me:
>>
>> root@debian:/userdata# ./aer-inject aer.txt
>> [   17.764272] pcieport 0000:00:00.0: aer_inject: Injecting errors
>> 00000040/00000000 into device 0000:01:00.0
>> [   17.765178] aer_isr ! #log I added in aer_isr
>> [   17.765394] pcieport 0000:00:00.0: AER: Correctable error message
>> received from 0000:01:00.0
>> [   17.766211] nvme 0000:01:00.0: PCIe Bus Error: severity=Correctable,
>> type=Data Link Layer, (Receiver ID)
>> root@debian:/userdata# [   17.767045] nvme 0000:01:00.0:   device
>> [144d:a80a] error status/mask=00000040/0000e000
>> [   17.767980] nvme 0000:01:00.0:    [ 6] BadTLP
>>
>> root@debian:/userdata# cat /proc/interrupts | grep aerdrv
>>   60:      0      0      0      0      0      0     0     0     INTx   0 Edge
>> PCIe PME, aerdrv, PCIe bwctrl
>>   63:      0      0      0      1      0      0     0     0     INTx   0 Edge
>> PCIe PME, aerdrv
>> 110:      0      0      0      0      0      0     0     0     INTx   0 Edge
>> PCIe PME, aerdrv
>>
>>>
>>>>> +		dw_pcie_remove_capability(pci, PCI_CAP_ID_MSI);
>>>>> +		dw_pcie_remove_capability(pci, PCI_CAP_ID_MSIX);
>>>>
>>>> Will it make all devices connected to use INTx only?
>>>>
>>>
>>> Nah, it is just for the Root Port. The MSI/MSI-X from endpoint devices will
>>> continue to work as usual.
>>
>> Qiang Yu,
>>
>> Could you please help your IP version with below patch?
>> It's in hex format, you could convert each pair of hex
>> characters to ASCII, i.g, 0x3437302a is 4.70a. The reason
>> is we asked Synopsys to help check this issue before, then
>> we were informed that they have supported it at least since
>> IP version 6.0x. So we may have to limit the version first.
>>
> 
> Hi Shawn,
> 
> I checked the IP version of PCIe core on glymur, it is 6.00a (0x3630302A)
> and iMSI-RX still can't generate MSI for rootport.
> 

Thanks for let me know. I have no doubt about this patch, it works
for me as well.

> - Qiang Yu
>> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
>> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
>> @@ -1057,6 +1057,10 @@ int dw_pcie_setup_rc(struct dw_pcie_rp *pp)
>>
>>          dw_pcie_msi_init(pp);
>>
>> +#define PORT_LOGIC_PCIE_VERSION_NUMBER_OFF 0x8f8
>> +       val = dw_pcie_readl_dbi(pci, PORT_LOGIC_PCIE_VERSION_NUMBER_OFF);
>> +       printk("version = 0x%x\n", val);
>> +
>>
>>
>>
> 
>