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Message-ID: <ab1f7c51-bc41-4774-a0dc-850e53c412eb@mailbox.org>
Date: Wed, 22 Oct 2025 08:59:19 +0200
From: Stefan Roese <stefan.roese@...lbox.org>
To: Bjorn Helgaas <helgaas@...nel.org>, "Bandi, Ravi Kumar" <ravib@...zon.com>
Cc: "mani@...nel.org" <mani@...nel.org>,
"thippeswamy.havalige@....com" <thippeswamy.havalige@....com>,
"lpieralisi@...nel.org" <lpieralisi@...nel.org>,
"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"kwilczynski@...nel.org" <kwilczynski@...nel.org>,
"robh@...nel.org" <robh@...nel.org>,
"michal.simek@....com" <michal.simek@....com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"stable@...r.kernel.org" <stable@...r.kernel.org>,
Sean Anderson <sean.anderson@...ux.dev>
Subject: Re: [PATCH v2] PCI: xilinx-xdma: Enable INTx interrupts
Hi Bjorn,
Hi Ravi,
On 10/21/25 23:28, Bjorn Helgaas wrote:
> On Tue, Oct 21, 2025 at 08:55:41PM +0000, Bandi, Ravi Kumar wrote:
>>> On Tue, Oct 21, 2025 at 05:46:17PM +0000, Bandi, Ravi Kumar wrote:
>>>>> On Oct 21, 2025, at 10:23 AM, Bjorn Helgaas <helgaas@...nel.org> wrote:
>>>>> On Sat, Sep 20, 2025 at 10:52:32PM +0000, Ravi Kumar Bandi wrote:
>>>>>> The pcie-xilinx-dma-pl driver does not enable INTx interrupts
>>>>>> after initializing the port, preventing INTx interrupts from
>>>>>> PCIe endpoints from flowing through the Xilinx XDMA root port
>>>>>> bridge. This issue affects kernel 6.6.0 and later versions.
>>>>>>
>>>>>> This patch allows INTx interrupts generated by PCIe endpoints
>>>>>> to flow through the root port. Tested the fix on a board with
>>>>>> two endpoints generating INTx interrupts. Interrupts are
>>>>>> properly detected and serviced. The /proc/interrupts output
>>>>>> shows:
>>>>>>
>>>>>> [...]
>>>>>> 32: 320 0 pl_dma:RC-Event 16 Level 400000000.axi-pcie, azdrv
>>>>>> 52: 470 0 pl_dma:RC-Event 16 Level 500000000.axi-pcie, azdrv
>>>>>> [...]
First a comment on this IRQ logging:
These lines do NOT refer to the INTx IRQ(s) but the controller internal
"events" (errors etc). Please see this log for INTx on my Versal
platform with pci_irqd_intx_xlate added:
24: 0 0 pl_dma:RC-Event 0 Level LINK_DOWN
25: 0 0 pl_dma:RC-Event 3 Level HOT_RESET
26: 0 0 pl_dma:RC-Event 8 Level CFG_TIMEOUT
27: 0 0 pl_dma:RC-Event 9 Level CORRECTABLE
28: 0 0 pl_dma:RC-Event 10 Level NONFATAL
29: 0 0 pl_dma:RC-Event 11 Level FATAL
30: 0 0 pl_dma:RC-Event 20 Level SLV_UNSUPP
31: 0 0 pl_dma:RC-Event 21 Level SLV_UNEXP
32: 0 0 pl_dma:RC-Event 22 Level SLV_COMPL
33: 0 0 pl_dma:RC-Event 23 Level SLV_ERRP
34: 0 0 pl_dma:RC-Event 24 Level SLV_CMPABT
35: 0 0 pl_dma:RC-Event 25 Level SLV_ILLBUR
36: 0 0 pl_dma:RC-Event 26 Level MST_DECERR
37: 0 0 pl_dma:RC-Event 27 Level MST_SLVERR
38: 94 0 pl_dma:RC-Event 16 Level 84000000.axi-pcie
39: 94 0 pl_dma:INTx 0 Level nvme0q0, nvme0q1
The last line shows the INTx IRQs here ('pl_dma:INTx' vs 'pl_dma:RC-
Event').
More below...
>>>>>>
>>>>>> Changes since v1::
>>>>>> - Fixed commit message per reviewer's comments
>>>>>>
>>>>>> Fixes: 8d786149d78c ("PCI: xilinx-xdma: Add Xilinx XDMA Root Port driver")
>>>>>> Cc: stable@...r.kernel.org
>>>>>> Signed-off-by: Ravi Kumar Bandi <ravib@...zon.com>
>>>>>
>>>>> Hi Ravi, obviously you tested this, but I don't know how to reconcile
>>>>> this with Stefan's INTx fix at
>>>>> https://lore.kernel.org/r/20251021154322.973640-1-stefan.roese@mailbox.org
>>>>>
>>>>> Does Stefan's fix need to be squashed into this patch?
>>>>
>>>> Sure, we can squash Stefan’s fix into this.
>>>
>>> I know we *can* squash them.
>>>
>>> I want to know why things worked for you and Stefan when they
>>> *weren't* squashed:
>>>
>>> - Why did INTx work for you even without Stefan's patch. Did you
>>> get INTx interrupts but not the right ones, e.g., did the device
>>> signal INTA but it was received as INTB?
>>
>> I saw that interrupts were being generated by the endpoint device,
>> but I didn’t specifically check if they were correctly translated in
>> the controller. I noticed that the new driver wasn't explicitly
>> enabling the interrupts, so my first approach was to enable them,
>> which helped the interrupts flow through.
>
> OK, I'll assume the interrupts happened but the driver might not have
> been able to handle them correctly, e.g., it was prepared for INTA but
> got INTB or similar.
>
>>> - Why did Stefan's patch work for him even without your patch. How
>>> could Stefan's INTx work without the CSR writes to enable
>>> interrupts?
>>
>> I'm not entirely sure if there are any other dependencies in the
>> FPGA bitstream. I'll investigate further and get back to you.
>
> Stefan clarified in a private message that he had applied your patch
> first, so this mystery is solved.
Yes. I applied Ravi's patch first and still got no INTx delivered
to the nvme driver. That's what me triggered to dig deeper here and
resulted in this v2 patch with pci_irqd_intx_xlate added.
BTW:
I re-tested just now w/o Ravi's patch and the INTx worked. Still I think
Ravi's patch is valid and should be applied...
>>> - Why you mentioned "kernel 6.6.0 and later versions."
>>> 8d786149d78c appeared in v6.7, so why would v6.6.0 would be
>>> affected?
>>
>> Apologies for not clearly mentioning the version earlier. This is
>> from the linux-xlnx tree on the xlnx_rebase_v6.6 branch, which
>> includes the new Xilinx root port driver with QDMA support:
>> https://github.com/Xilinx/linux-xlnx/blob/xlnx_rebase_v6.6_LTS/drivers/pci/controller/pcie-xilinx-dma-pl.c
>>
>> In earlier versions, the driver was:
>> https://github.com/Xilinx/linux-xlnx/blob/xlnx_rebase_v6.1_LTS_2023.1_update/drivers/pci/controller/pcie-xdma-pl.c
>> This older driver had no issues with interrupts.
>>
>> The new driver introduced in v6.7 and later is a rewrite of the old
>> one, now with QDMA support, which has issues with INTx interrupts.
>
> OK, this sounds like out-of-tree history that is not relevant in the
> mainline kernel, so Mani did the right thing in omitting it.
>
> I think the best thing to do is to squash Stefan's patch into this one
> so we end up with a single patch that makes INTx work correctly.
>
> Ravi and Stefan, does that seem OK to you?
Yes, please either apply both separately or squash them. Whatever you
prefer.
Many thanks,
Stefan
>>>>>> +++ b/drivers/pci/controller/pcie-xilinx-dma-pl.c
>>>>>> @@ -659,6 +659,12 @@ static int xilinx_pl_dma_pcie_setup_irq(struct pl_dma_pcie *port)
>>>>>> return err;
>>>>>> }
>>>>>>
>>>>>> + /* Enable interrupts */
>>>>>> + pcie_write(port, XILINX_PCIE_DMA_IMR_ALL_MASK,
>>>>>> + XILINX_PCIE_DMA_REG_IMR);
>>>>>> + pcie_write(port, XILINX_PCIE_DMA_IDRN_MASK,
>>>>>> + XILINX_PCIE_DMA_REG_IDRN_MASK);
>>>>>> +
>>>>>> return 0;
>>>>>> }
>>
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