linux-kernel - Re: [PATCH v5 7/9] PCI: PCI: Add pcie_link_is_active() to determine if the PCIe link is active

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Message-ID: <1f998456-2d4e-0208-9018-a934aed84b8f@oss.qualcomm.com>
Date: Mon, 14 Apr 2025 09:53:50 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: Lukas Wunner <lukas@...ner.de>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczy??ski <kw@...ux.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        chaitanya chundru <quic_krichai@...cinc.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        cros-qcom-dts-watchers@...omium.org, Jingoo Han <jingoohan1@...il.com>,
        Bartosz Golaszewski <brgl@...ev.pl>, quic_vbadigan@...cnic.com,
        amitk@...nel.org, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, jorge.ramirez@....qualcomm.com,
        Dmitry Baryshkov <lumag@...nel.org>
Subject: Re: [PATCH v5 7/9] PCI: PCI: Add pcie_link_is_active() to determine
 if the PCIe link is active



On 4/12/2025 9:22 AM, Lukas Wunner wrote:
> On Sat, Apr 12, 2025 at 07:19:56AM +0530, Krishna Chaitanya Chundru wrote:
>> Introduce a common API to check if the PCIe link is active, replacing
>> duplicate code in multiple locations.
>>
>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> 
> Reviewed-by: Lukas Wunner <lukas@...ner.de>
> 
> One heads-up and one nit:
> 
>> --- a/drivers/pci/hotplug/pciehp_hpc.c
>> +++ b/drivers/pci/hotplug/pciehp_hpc.c
>> @@ -584,7 +557,7 @@ static void pciehp_ignore_dpc_link_change(struct controller *ctrl,
>>   	 * Synthesize it to ensure that it is acted on.
>>   	 */
>>   	down_read_nested(&ctrl->reset_lock, ctrl->depth);
>> -	if (!pciehp_check_link_active(ctrl))
>> +	if (!pcie_link_is_active(ctrl_dev(ctrl)))
>>   		pciehp_request(ctrl, PCI_EXP_SLTSTA_DLLSC);
>>   	up_read(&ctrl->reset_lock);
>>   }
> 
> Heads-up:  There's a trivial merge conflict here with what's queued on
> pci.git/hotplug.  No need for you to respin because I expect this will be
> merged through a different topic branch anyway, but Bjorn and the other
> maintainers will see the merge conflict when generating the next branch.
> 
> 
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -1945,6 +1945,7 @@ pci_release_mem_regions(struct pci_dev *pdev)
>>   			    pci_select_bars(pdev, IORESOURCE_MEM));
>>   }
>>   
>> +bool pcie_link_is_active(struct pci_dev *dev);
>>   #else /* CONFIG_PCI is not enabled */
>>   
>>   static inline void pci_set_flags(int flags) { }
>> @@ -2093,6 +2094,9 @@ pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
>>   {
>>   	return -ENOSPC;
>>   }
>> +
>> +static inline bool pcie_link_is_active(struct pci_dev *dev)
>> +{ return false; }
>>   #endif /* CONFIG_PCI */
> 
> Nit:  Seems like this would still fit within 80 chars:
> 
> static inline bool pcie_link_is_active(struct pci_dev *dev) { return false; }
> 
> That said, all existing callers of this function as well as the new one
> introduced by this series are only compiled in the CONFIG_PCI=y case,
> so I'm not sure the inline stub is necessary at all?
> 
If any other driver other than these two drivers in future wants to use
this API, it can be useful in that case.

- Krishna Chaitanya.
> Thanks,
> 
> Lukas