linux-kernel - Re: [PATCH 4/6] wifi: ath12k: Use pci_{enable/disable}_link_state() APIs to enable/disable ASPM states

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Message-ID: <aa2f6350-3235-422b-be04-a03bd3a1010d@oss.qualcomm.com>
Date: Fri, 18 Jul 2025 13:33:46 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: Manivannan Sadhasivam <mani@...nel.org>,
        Baochen Qiang <baochen.qiang@....qualcomm.com>
Cc: manivannan.sadhasivam@....qualcomm.com,
        Jeff Johnson
 <jjohnson@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kwilczynski@...nel.org>,
        Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
        Nirmal Patel <nirmal.patel@...ux.intel.com>,
        Jonathan Derrick <jonathan.derrick@...ux.dev>,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        ath12k@...ts.infradead.org, ath11k@...ts.infradead.org,
        ath10k@...ts.infradead.org, Bjorn Helgaas <helgaas@...nel.org>,
        ilpo.jarvinen@...ux.intel.com, linux-arm-msm@...r.kernel.org,
        linux-pci@...r.kernel.org, Qiang Yu <qiang.yu@....qualcomm.com>
Subject: Re: [PATCH 4/6] wifi: ath12k: Use pci_{enable/disable}_link_state()
 APIs to enable/disable ASPM states



On 7/18/2025 1:27 PM, Manivannan Sadhasivam wrote:
> On Fri, Jul 18, 2025 at 10:05:02AM GMT, Baochen Qiang wrote:
>>
>>
>> On 7/17/2025 7:29 PM, Manivannan Sadhasivam wrote:
>>> On Thu, Jul 17, 2025 at 06:46:12PM GMT, Baochen Qiang wrote:
>>>>
>>>>
>>>> On 7/17/2025 6:31 PM, Manivannan Sadhasivam wrote:
>>>>> On Thu, Jul 17, 2025 at 05:24:13PM GMT, Baochen Qiang wrote:
>>>>>
>>>>> [...]
>>>>>
>>>>>>> @@ -16,6 +16,8 @@
>>>>>>>   #include "mhi.h"
>>>>>>>   #include "debug.h"
>>>>>>>   
>>>>>>> +#include "../ath.h"
>>>>>>> +
>>>>>>>   #define ATH12K_PCI_BAR_NUM		0
>>>>>>>   #define ATH12K_PCI_DMA_MASK		36
>>>>>>>   
>>>>>>> @@ -928,8 +930,7 @@ static void ath12k_pci_aspm_disable(struct ath12k_pci *ab_pci)
>>>>>>>   		   u16_get_bits(ab_pci->link_ctl, PCI_EXP_LNKCTL_ASPM_L1));
>>>>>>>   
>>>>>>>   	/* disable L0s and L1 */
>>>>>>> -	pcie_capability_clear_word(ab_pci->pdev, PCI_EXP_LNKCTL,
>>>>>>> -				   PCI_EXP_LNKCTL_ASPMC);
>>>>>>> +	pci_disable_link_state(ab_pci->pdev, PCIE_LINK_STATE_L0S | PCIE_LINK_STATE_L1);
>>>>>>
>>>>>> Not always, but sometimes seems the 'disable' does not work:
>>>>>>
>>>>>> [  279.920507] ath12k_pci_power_up 1475: link_ctl 0x43 //before disable
>>>>>> [  279.920539] ath12k_pci_power_up 1482: link_ctl 0x43 //after disable
>>>>>>
>>>>>>
>>>>>>>   
>>>>>>>   	set_bit(ATH12K_PCI_ASPM_RESTORE, &ab_pci->flags);
>>>>>>>   }
>>>>>>> @@ -958,10 +959,7 @@ static void ath12k_pci_aspm_restore(struct ath12k_pci *ab_pci)
>>>>>>>   {
>>>>>>>   	if (ab_pci->ab->hw_params->supports_aspm &&
>>>>>>>   	    test_and_clear_bit(ATH12K_PCI_ASPM_RESTORE, &ab_pci->flags))
>>>>>>> -		pcie_capability_clear_and_set_word(ab_pci->pdev, PCI_EXP_LNKCTL,
>>>>>>> -						   PCI_EXP_LNKCTL_ASPMC,
>>>>>>> -						   ab_pci->link_ctl &
>>>>>>> -						   PCI_EXP_LNKCTL_ASPMC);
>>>>>>> +		pci_enable_link_state(ab_pci->pdev, ath_pci_aspm_state(ab_pci->link_ctl));
>>>>>>
>>>>>> always, the 'enable' is not working:
>>>>>>
>>>>>> [  280.561762] ath12k_pci_start 1180: link_ctl 0x43 //before restore
>>>>>> [  280.561809] ath12k_pci_start 1185: link_ctl 0x42 //after restore
>>>>>>
>>>>>
>>>>> Interesting! I applied your diff and I never see this issue so far (across 10+
>>>>> reboots):
>>>>
>>>> I was not testing reboot. Here is what I am doing:
>>>>
>>>> step1: rmmod ath12k
>>>> step2: force LinkCtrl using setpci (make sure it is 0x43, which seems more likely to see
>>>> the issue)
>>>>
>>>> 	sudo setpci -s 02:00.0 0x80.B=0x43
>>>>
>>>> step3: insmod ath12k and check linkctrl
>>>>
>>>
>>> So I did the same and got:
>>>
>>> [ 3283.363569] ath12k_pci_power_up 1475: link_ctl 0x43
>>> [ 3283.363769] ath12k_pci_power_up 1480: link_ctl 0x40
>>> [ 3284.007661] ath12k_pci_start 1180: link_ctl 0x40
>>> [ 3284.007826] ath12k_pci_start 1185: link_ctl 0x42
>>>
>>> My host machine is Qcom based Thinkpad T14s and it doesn't support L0s. So
>>> that's why the lnkctl value once enabled becomes 0x42. This is exactly the
>>> reason why the drivers should not muck around LNKCTL register manually.
>>
>> Thanks, then the 0x43 -> 0x40 -> 0x40 -> 0x42 sequence should not be a concern. But still
>> the random 0x43 -> 0x43 -> 0x43 -> 0x42 sequence seems problematic.
>>
>> How many iterations have you done with above steps? From my side it seems random so better
>> to do some stress test.
>>
> 
> So I ran the modprobe for about 50 times on the Intel NUC that has QCA6390, but
> didn't spot the disparity. This is the script I used:
> 
> for i in {1..50} ;do echo "Loop $i"; sudo setpci -s 01:00.0 0x80.B=0x43;\
> sudo modprobe -r ath11k_pci; sleep 1; sudo modprobe ath11k_pci; sleep 1;done
> 
> And I always got:
> 
> [ 5862.388083] ath11k_pci_aspm_disable: 609 lnkctrl: 0x43
> [ 5862.388124] ath11k_pci_aspm_disable: 614 lnkctrl: 0x40
> [ 5862.876291] ath11k_pci_start: 880 lnkctrl: 0x40
> [ 5862.876346] ath11k_pci_start: 886 lnkctrl: 0x42
> 
> Also no AER messages. TBH, I'm not sure how you were able to see the random
> issues with these APIs. That looks like a race, which is scary.
> 
How about using locked variants pci_disable_link_state_locked &
pci_enable_link_state_locked give it a try?

- Krishna Chaitanya
> I do not want to ignore your scenario, but would like to reproduce and get to
> the bottom of it.
> 
> - Mani
>