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: <gx5gruyhrhwhvwkiqlkp2bggqd4oqe4quvqiiphfzolhjtzun6@okogvabkqah3>
Date: Fri, 18 Jul 2025 13:27:14 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: 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, Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>, 
	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 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.

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

- Mani

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