linux-kernel - Re: [PATCH v6 3/8] dt-bindings: PCI: qcom,pcie-x1e80100: Add 'global' interrupt

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Message-ID: <75b22700-e4de-43fd-8e16-1961703bb708@quicinc.com>
Date: Mon, 14 Oct 2024 21:09:18 +0800
From: Qiang Yu <quic_qianyu@...cinc.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        "Krzysztof
 Kozlowski" <krzk@...nel.org>
CC: <vkoul@...nel.org>, <kishon@...nel.org>, <robh@...nel.org>,
        <andersson@...nel.org>, <konradybcio@...nel.org>, <krzk+dt@...nel.org>,
        <conor+dt@...nel.org>, <mturquette@...libre.com>, <sboyd@...nel.org>,
        <abel.vesa@...aro.org>, <quic_msarkar@...cinc.com>,
        <quic_devipriy@...cinc.com>, <dmitry.baryshkov@...aro.org>,
        <kw@...ux.com>, <lpieralisi@...nel.org>, <neil.armstrong@...aro.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-phy@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v6 3/8] dt-bindings: PCI: qcom,pcie-x1e80100: Add 'global'
 interrupt


On 10/14/2024 5:41 PM, Manivannan Sadhasivam wrote:
>
> On October 14, 2024 2:56:58 PM GMT+05:30, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>> On 14/10/2024 11:02, Manivannan Sadhasivam wrote:
>>> On Fri, Oct 11, 2024 at 06:06:02PM +0200, Krzysztof Kozlowski wrote:
>>>> On 11/10/2024 17:51, Manivannan Sadhasivam wrote:
>>>>>
>>>>> On October 11, 2024 9:14:31 PM GMT+05:30, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>>>>>> On 11/10/2024 17:42, Manivannan Sadhasivam wrote:
>>>>>>>
>>>>>>> On October 11, 2024 8:03:58 PM GMT+05:30, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>>>>>>>> On Fri, Oct 11, 2024 at 03:41:37AM -0700, Qiang Yu wrote:
>>>>>>>>> Document 'global' SPI interrupt along with the existing MSI interrupts so
>>>>>>>>> that QCOM PCIe RC driver can make use of it to get events such as PCIe
>>>>>>>>> link specific events, safety events, etc.
>>>>>>>> Describe the hardware, not what the driver will do.
>>>>>>>>
>>>>>>>>> Though adding a new interrupt will break the ABI, it is required to
>>>>>>>>> accurately describe the hardware.
>>>>>>>> That's poor reason. Hardware was described and missing optional piece
>>>>>>>> (because according to your description above everything was working
>>>>>>>> fine) is not needed to break ABI.
>>>>>>>>
>>>>>>> Hardware was described but not completely. 'global' IRQ let's the controller driver to handle PCIe link specific events like Link up, Link down etc... They improve user experience like the driver can use those interrupts to start bus enumeration on its own. So breaking the ABI for good in this case.
>>>>>>>
>>>>>>>> Sorry, if your driver changes the ABI for this poor reason.
>>>>>>>>
>>>>>>> Is the above reasoning sufficient?
>>>>>> I tried to look for corresponding driver change, but could not, so maybe
>>>>>> there is no ABI break in the first place.
>>>>> Here it is:
>>>>>
>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4581403f67929d02c197cb187c4e1e811c9e762a
>>>>>
>>>>>   Above explanation is good, but
>>>>>> still feels like improvement and device could work without global clock.
>>>> So there is no ABI break in the first place... Commit is misleading.
>>>>
>>> It increases the 'minItems' to 9 from 8, how come it is not an ABI break?
>> Interface changed but all known users are still working, right? "Break"
>> means something does not work, something is affected.
> Hmm. I thought you were referring to the DTS warnings (for old DTS) that come out of these changes. But for kernel ABI, yes there is no breakage.
I really see dts warning after dtbs checking and since global irq is to
improve user experience and device could still work without it, will
keep the 'minItems' as 8 and set 'maxItems' as 9.

Thanks
Qiang
>
> Sorry for the confusion.
>
> - Mani
>
>> I might be missing
>> here something, of course, but I simply do not see any affected user here.
>>
>> Best regards,
>> Krzysztof
>>
>>
> மணிவண்ணன் சதாசிவம்