From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CAB413002C8; Fri, 16 Oct 2026 22:09:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792188544; cv=none; b=EagbB9QIaHkJCQ4AXf2Y4/+kCsUcx2QcOxfCy9tassSMiUVN4XjlRDXAF4lM2GSN+z7cXShym9ZkTh0M879iV+YcnrAlkH6clVht2uYc01vnPlEcMpARqx8kB7biKojebm/p0Vnh7ScepJ1PKfOCGGH+hswM716qL6BGuCeMH+o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792188544; c=relaxed/simple; bh=qhvyOQ6SrOloWF/DiJ0gD5TqhPaHiae6yEIJDwqQ2Ew=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=W68Su+fYCdtHA9RpKyCnvAka8umw+SN9uykF7hy/edK8yyP+9sZa96WBcBGsTSBVuPAZdDf36x51hFxChjD8Bvqvj8NO53qj3E/aJ8yDYuGqeMqYmNZlFa64SFC/ZDiVdctPg0pNxaAGGKb8NqChssfl6bCF7/NwdBw3v8Vm798= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EojSRKfd; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EojSRKfd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2DCA71F000C4; Fri, 16 Oct 2026 22:09:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792188542; bh=N+IfVEDNy7weUr9N7uxvL6jLCprKtx2WdtJneeQTuEA=; h=Date:From:To:Cc:Subject:In-Reply-To; b=EojSRKfdAM9oDuZ9jF49SMiBF3zj2wdWEu49eIsy3J6zDbtd5vPg2v/7x6ZxGZLnr M19eONTst4yrehj4leYPBDh/0lSll7/t5ZLf4sN5sCARPjoFdCe22YtDn3o0ux2ImM 6wRzpjWENrr5zssGC8fwJ/t3RTxGutllXA7KxfBobVmcxIPmDtuA48p0xITxIMuV/q q5WBy1j/xLSy/sDeH16G5ErFv8zmjbftYoLSj0V9IZF2Zr9vx2clPHCDnK/qru0FQN 2YdalWq3HyVVbzfalQuO1mSwrNVrhywb0ANPS53LvRbNfQUztrTkzcrnuesvkYiXa7 /CAlgq5HndODw== Date: Fri, 16 Oct 2026 17:09:00 -0500 From: Bjorn Helgaas To: Manivannan Sadhasivam Cc: Bjorn Helgaas , Lorenzo Pieralisi , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Rob Herring , Nirmal Patel , Jonathan Derrick , Jeff Johnson , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-wireless@vger.kernel.org, ath12k@lists.infradead.org, ath11k@lists.infradead.org, ath10k@lists.infradead.org, Krishna Chaitanya Chundru , Qiang Yu , Ilpo =?utf-8?B?SsOkcnZpbmVu?= , Emmanuel Grumbach , Matthew Garrett Subject: Re: [PATCH v3 0/8] PCI/ASPM: Add pci_force_enable_link_state() API and convert Atheros drivers Message-ID: <20261016220900.GA2020355@bhelgaas> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Fri, Oct 16, 2026 at 11:28:03AM +0530, Manivannan Sadhasivam wrote: > On Wed, Oct 14, 2026 at 03:51:17PM -0500, Bjorn Helgaas wrote: > > [+cc Emmanuel, Matthew] > > > > On Wed, Jul 08, 2026 at 04:30:14PM +0200, Manivannan Sadhasivam wrote: > > > Hi, > > > > > > This series converts the atheros WLAN drivers (ath10k/ath11k/ath12k) to > > > use the PCI core ASPM APIs for enabling/disabling ASPM instead of writing > > > to the LNKCTL register directly. Touching LNKCTL behind the PCI core's > > > back leaves the ASPM service driver's view of the link state out of sync > > > with the hardware, which is not nice. > > > > > > The catch is that these drivers save the currently enabled ASPM states, > > > disable ASPM before firmware download, and restore the saved states > > > afterwards. pci_enable_link_state() cannot restore states that were > > > disabled via pci_disable_link_state() or blacklisted during init (like > > > the pre-1.1 device blacklist, which is only meant to be overridden with > > > pcie_aspm=force), and that is intentional. So the save/restore sequence > > > cannot be expressed with the existing APIs. > > > > > > In v2 I tried to fix this by making pci_enable_link_state*() symmetric > > > with the disable APIs, but as pointed out during review, that also ends > > > up overriding the init-time blacklist for every caller (including VMD), > > > which is not something we want. So instead, this version adds a separate > > > pci_force_enable_link_state() API (patch 2) that re-enables the requested > > > states unconditionally. The caller is responsible for only asking for > > > states the device actually supports, and the ath drivers do this by > > > restoring exactly what pcie_aspm_enabled() reported earlier. > > > > > > The first five patches touch the PCI core: patch 1 (from Ilpo) makes > > > pci_disable_link_state() disable ASPM unconditionally, patch 2 adds the > > > new API, patch 3 moves the D0 transition needed before enabling PCI-PM > > > L1 PM Substates (PCIe r6.0, sec 5.5.4) into the shared helper and drops > > > it from the vmd and pcie-qcom callers, patch 4 cleans up the kernel-doc, > > > and patch 5 makes pcie_aspm_enabled() return the enabled state mask so it > > > can be used for save/restore. The last three patches convert the ath > > > drivers. > > > > > > Testing > > > ======= > > > > > > I've tested this series on a Lenovo Thinkpad T14s with WCN7850 (so that's > > > just the ath12k driver). Rest of the drivers are compile tested only. > > > > > > Merging Strategy > > > ================ > > > > > > Even though there is no build dependency between the PCI core and atheros > > > patches, there is a functional dependency. So I'd recommend creating an > > > immutable branch with the PCI patches and merging that branch into both > > > the PCI and linux-wireless trees, and finally merging the atheros patches > > > into the linux-wireless tree. > > > > > > If the immutable branch seems like a hassle, then the PCI core patches > > > could get merged first and the atheros patches can wait for the next > > > cycle. > > > > > > - Mani > > > > > > Changes in v3: > > > * Dropped the change that made pci_enable_link_state*() symmetric with the > > > disable APIs. Instead added a new pci_force_enable_link_state() API used > > > only by the ath drivers, so the init-time blacklist stays overridable > > > only via pcie_aspm=force and existing callers like VMD are left > > > untouched. > > > * Fixed the locked path to use pci_set_power_state_locked() for the D0 > > > transition. The previous version called the non-locked variant, which > > > re-acquires pci_bus_sem. > > > * ath drivers now disable PCIE_LINK_STATE_ASPM_ALL instead of > > > PCIE_LINK_STATE_ALL so that CLKPM is preserved and can be restored > > > (pcie_aspm_enabled() doesn't report CLKPM). > > > * Reworked the kernel-doc patch to cover both the enable and disable APIs > > > and reference the new API. > > > * Rebased on top of v7.2-rc1. > > > > > > Changes in v2: > > > * Reworked the pcie_aspm_enabled() API to return the enabled states > > > instead of bool and used it to save/restore the ASPM states in ath > > > drivers. > > > * Added a patch from Ilpo to disable ASPM even if BIOS didn't grant > > > permission. > > > * Added the CONFIG_PCIEASPM dependency to ath{10/11/12}k drivers. > > > * Rebased on top of v6.17-rc1. > > > > > > Signed-off-by: Manivannan Sadhasivam > > > --- > > > Ilpo Järvinen (1): > > > PCI/ASPM: Always disable ASPM when driver requests it > > > > I put this first patch on pci/aspm for v7.4 because there seems to > > be a consensus that it's better to have the ASPM core disable > > things even if it doesn't technically have control of ASPM, > > because the alternative is that drivers just do it themselves, > > also ignoring ASPM ownership concerns. Having the drivers do it > > just means the PCI core ASPM support doesn't know what's > > happening. > > > > I think we should defer the rest of these because I think there's > > a little room to make the enable/disable/force-enable dance more > > intuitive for the drivers. As far as I know, the rest of the > > series is definite cleanups but doesn't fix any actual functional > > issues. > > I wouldn't just categorize the rest of the patches as mere cleanups. > They are indeed fixing an obvious race between PCI core and the > driver doing ASPM dance at the same time. But for sure, even after > these patches, one can trigger the same race between sysfs 'config' > and the driver/PCI core, but that's more of an user trying to > perform an action to trigger a race vs race happening within the > kernel without user intervention (which is too bad). You're right, using "cleanup" glosses over important fixes. It's a significant consistency problem for PCI core ASPM code as well as racing. Although I'm not sure there is actually a race between the driver and the PCI core *except* for sysfs. In what non-sysfs case might the core ASPM code touch the device at the same time as the driver? I guess maybe lane margining and bwctrl? Can those happen autonomously, without being kicked via sysfs? > I'd really like to see a way forward for these patches, even with a > new API and not let them fall through the cracks. Absolutely!