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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VitDl0P2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VitDl0P2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 812F3C4CEEB; Fri, 18 Jul 2025 16:26:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752855963; bh=aXCC6a0BRcLONBCEG+qLtT+Rm3FPzL7V91riur1H9Xg=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=VitDl0P293UBhnBWTfwW9kVJK0g1L/RqqX2mGlwmW2JmETRPxtereKE2Vuq0LK+EG bf8x/QDXwtgdesGEGkf9l3+tOv/u5eMPMLfDd5Jm8tmNgi/l9dkuuL+h79ov7lthlp UFI2NSU7GD4fAKI/DAVKgV5+ZvEGjKu37s3kDh3BO2tZWRiDjhL2lKGk1Q0vG+z9uf wI7zXsu3ola9AnO/2kZYI7KblB/WNrwX/y89x0GMfAWLCxdr3YZUcYLqkv2y4YdPhH a+Wk/8evsszEwS9hOiOwuRm74mqj4lvhO6udfWVIb4fa6/y07B1q7rkveAwQJ6a9dO Qcy/kMyM8zjbQ== Date: Fri, 18 Jul 2025 11:26:00 -0500 From: Bjorn Helgaas To: Manivannan Sadhasivam Cc: Baochen Qiang , manivannan.sadhasivam@oss.qualcomm.com, Jeff Johnson , Lorenzo Pieralisi , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Rob Herring , Bjorn Helgaas , Nirmal Patel , Jonathan Derrick , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, ath12k@lists.infradead.org, ath11k@lists.infradead.org, ath10k@lists.infradead.org, ilpo.jarvinen@linux.intel.com, linux-arm-msm@vger.kernel.org, linux-pci@vger.kernel.org, Krishna Chaitanya Chundru , Qiang Yu Subject: Re: [PATCH 4/6] wifi: ath12k: Use pci_{enable/disable}_link_state() APIs to enable/disable ASPM states Message-ID: <20250718162600.GA2700538@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jul 18, 2025 at 05:19:28PM +0530, Manivannan Sadhasivam wrote: > On Fri, Jul 18, 2025 at 07:05:03PM GMT, Baochen Qiang wrote: > > On 7/18/2025 6:20 PM, Manivannan Sadhasivam wrote: > > > On Fri, Jul 18, 2025 at 01:27:27PM GMT, 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. > > >> > > >> I do not want to ignore your scenario, but would like to > > >> reproduce and get to the bottom of it. > > > > > > I synced with Baochen internally and able to repro the issue. > > > Ths issue is due to hand modifying the LNKCTL register from > > > userspace. The PCI core maintains the ASPM state internally and > > > uses it to change the state when the > > > pci_{enable/disable}_link_state*() APIs are called. > > > > > > So if the userspace or a client driver modifies the LNKCTL > > > register manually, it makes the PCI cached ASPM states invalid. > > > So while this series fixes the driver from doing that, nothing > > > prevents userspace from doing so using 'setpci' and other tools. > > > Userspace should only use sysfs attributes to change the state > > > and avoid modifying the PCI registers when the PCI core is > > > controlling the device. So this is the reason behind the > > > errantic behavior of the API and it is not due to the issue with > > > the API or the PCI core. > > > > IMO we can not rely on userspace doing what or not doing what, or > > on how it is doing, right? So can we fix PCI core to avoid this? > > I'm not sure it is possible to *fix* the PCI core here. Since the > PCI core gives userspace access to the entire config space of the > device, the userspace reads/writes to any of the registers it want. > So unless the config space access if forbidden if a driver is bound > to the device, it is inevitable. And then there is also /dev/mem... > > Interestingly, there is an API available for this purpose: > pci_request_config_region_exclusive(), but it is used only by the > AMD arch driver to prevent userspace from writing to the entire > config space of the device. > > Maybe it makes sense to use something like this to prevent the > userspace access to the entire config space if the driver is bind to > the device. I'm not really a fan of pci_request_config_region_exclusive() because it's such a singleton thing. I don't like to be one of only a few users of an interface. Linux has a long tradition of allowing root users to shoot themselves in the foot, and setpci is very useful as a debugging tool. Maybe tainting the kernel for config writes from userspace, and possibly even a WARN_ONCE() at the time, would be a compromise. Bjorn