From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailbackend.panix.com (mailbackend.panix.com [166.84.1.89]) (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 9F2F028D8ED; Thu, 4 Sep 2025 21:12:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=166.84.1.89 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757020352; cv=none; b=rtcND+PbzORq8NjKF0zKEvybMg62Q1F1rrnPW/YsnoWthKM/tyrrAsy2JBHnDscwcHqN4VoHG87KTDyOsju9efxPZ2PHmt+lAl2w6Yn3nFpfcYKKfgBDAA3UBvjn+qnwoc1oHD3R50RuiuqxWFmankcK9y65eC5yM8AH1tvbUCs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757020352; c=relaxed/simple; bh=bVpTdvqZQwctg8yn5l2gjB3RXA0ZvRDSr4BwQH5FB5E=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UVL6/sEtUkg6taj9tV0aTBn1SIiRea4wHRH88dvcVOZgauDhnyaTvaG8FAVRnCGw1bj1WeMuVtlztX0vEH0M9fmDFC6KDN1y3L00zXv+GOWELn/j1D6hijEPRfoRJ2gVZH5v5IeZ1o7LFW/F87Bo7+1JriS/tJ10adZzv+7yMmU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=panix.com; spf=pass smtp.mailfrom=panix.com; dkim=pass (1024-bit key) header.d=panix.com header.i=@panix.com header.b=GOLXty3e; arc=none smtp.client-ip=166.84.1.89 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=panix.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=panix.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=panix.com header.i=@panix.com header.b="GOLXty3e" Received: from [192.168.8.212] (kenny-tx.gotdns.com [162.196.229.233]) by mailbackend.panix.com (Postfix) with ESMTPSA id 4cHscr5Hz7z1CFP; Thu, 4 Sep 2025 17:12:28 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=panix.com; s=panix; t=1757020349; bh=bVpTdvqZQwctg8yn5l2gjB3RXA0ZvRDSr4BwQH5FB5E=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=GOLXty3eTWhG1W11NvdnOztq1grcyUiovXv1N9gz0Y6BDajpNX9G0MoZSlknbGIPH O1x/lQX5d7Ihd39CT7Y093K6tStW9xvl3aiHdi9TV4ZgA3afINZmnTPJnZLF2doKZ7 rQlN/ghaqifZG9RztbaB6/RL7M6akVEuz82JbYjs= Message-ID: <7242c456-ca01-4212-96d4-73e63ad0d5d3@panix.com> Date: Thu, 4 Sep 2025 14:12:27 -0700 Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V3 1/2] PCI/ASPM: Add host-bridge API to override default ASPM/CLKPM link state To: "David E. Box" , rafael@kernel.org, bhelgaas@google.com, vicamo.yang@canonical.com, ilpo.jarvinen@linux.intel.com, nirmal.patel@linux.intel.com, mani@kernel.org Cc: linux-pm@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250825203542.3502368-1-david.e.box@linux.intel.com> Content-Language: en-US From: Kenneth Crudup In-Reply-To: <20250825203542.3502368-1-david.e.box@linux.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Tested-by: Kenneth R. Crudup On 8/25/25 13:35, David E. Box wrote: > Synthetic PCIe hierarchies, such as those created by Intel VMD, are not > enumerated by firmware and do not receive BIOS-provided ASPM or CLKPM > defaults. Devices in such domains may therefore run without the intended > power management. > > Add a host-bridge mechanism that lets controller drivers supply their own > defaults. A new aspm_default_link_state field in struct pci_host_bridge is > set via pci_host_set_default_pcie_link_state(). During link initialization, > if this field is non-zero, ASPM and CLKPM defaults come from it instead of > BIOS. > > This enables drivers like VMD to align link power management with platform > expectations and avoids embedding controller-specific quirks in ASPM core > logic. > > Link: https://patchwork.ozlabs.org/project/linux-pci/patch/20250720190140.2639200-1-david.e.box%40linux.intel.com/ > Signed-off-by: David E. Box > Tested-by: Manivannan Sadhasivam > Reviewed-by: Rafael J. Wysocki (Intel) > --- > Changes in V3: > -- Changed pci_host_get_default_pcie_link_state() argument name from > parent to dev. > -- Applied changelog tags > > Changes in V2: > > -- Host field name changed to aspm_default_link_state. > -- Added get/set functions for aspm_default_link_state. Only the > setter is exported. Added a kernel-doc describing usage and > particulars around meaning of 0. > > Changes in V1 from RFC: > > -- Rename field to aspm_dflt_link_state since it stores > PCIE_LINK_STATE_XXX flags, not a policy enum. > -- Move the field to struct pci_host_bridge since it's being applied to > the entire host bridge per Mani's suggestion. > -- During testing noticed that clkpm remained disabled and this was > also handled by the formerly used pci_enable_link_state(). Add a > check in pcie_clkpm_cap_init() as well to enable clkpm during init. > > drivers/pci/pcie/aspm.c | 42 +++++++++++++++++++++++++++++++++++++++-- > include/linux/pci.h | 9 +++++++++ > 2 files changed, 49 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c > index 919a05b97647..851ca3d68e55 100644 > --- a/drivers/pci/pcie/aspm.c > +++ b/drivers/pci/pcie/aspm.c > @@ -373,6 +373,39 @@ static void pcie_set_clkpm(struct pcie_link_state *link, int enable) > pcie_set_clkpm_nocheck(link, enable); > } > > +/** > + * pci_host_set_default_pcie_link_state - set controller-provided default ASPM/CLKPM mask > + * @host: host bridge on which to apply the defaults > + * @state: PCIE_LINK_STATE_XXX flags > + * > + * Allows a PCIe controller driver to specify the default ASPM and/or > + * Clock Power Management (CLKPM) link state mask that will be used > + * for links under this host bridge during ASPM/CLKPM capability init. > + * > + * The value is consumed in pcie_aspm_cap_init() and pcie_clkpm_cap_init() > + * to override the firmware-discovered defaults. > + * > + * Interpretation of aspm_default_link_state: > + * - Nonzero: bitmask of PCIE_LINK_STATE_* values to be used as defaults > + * - Zero: no override provided; ASPM/CLKPM defaults fall back to > + * values discovered in hardware/firmware > + * > + * Note: zero is always treated as "unset", not as "force ASPM/CLKPM off". > + */ > +void pci_host_set_default_pcie_link_state(struct pci_host_bridge *host, > + unsigned int state) > +{ > + host->aspm_default_link_state = state; > +} > +EXPORT_SYMBOL_GPL(pci_host_set_default_pcie_link_state); > + > +static u32 pci_host_get_default_pcie_link_state(struct pci_dev *dev) > +{ > + struct pci_host_bridge *host = pci_find_host_bridge(dev->bus); > + > + return host ? host->aspm_default_link_state : 0; > +} > + > static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist) > { > int capable = 1, enabled = 1; > @@ -394,7 +427,10 @@ static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist) > enabled = 0; > } > link->clkpm_enabled = enabled; > - link->clkpm_default = enabled; > + if (pci_host_get_default_pcie_link_state(link->pdev) & PCIE_LINK_STATE_CLKPM) > + link->clkpm_default = 1; > + else > + link->clkpm_default = enabled; > link->clkpm_capable = capable; > link->clkpm_disable = blacklist ? 1 : 0; > } > @@ -866,7 +902,9 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist) > } > > /* Save default state */ > - link->aspm_default = link->aspm_enabled; > + link->aspm_default = pci_host_get_default_pcie_link_state(parent); > + if (!link->aspm_default) > + link->aspm_default = link->aspm_enabled; > > /* Setup initial capable state. Will be updated later */ > link->aspm_capable = link->aspm_support; > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 59876de13860..8947cbaf9fa6 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -620,6 +620,10 @@ struct pci_host_bridge { > unsigned int size_windows:1; /* Enable root bus sizing */ > unsigned int msi_domain:1; /* Bridge wants MSI domain */ > > +#ifdef CONFIG_PCIEASPM > + unsigned int aspm_default_link_state; /* Controller-provided default */ > +#endif > + > /* Resource alignment requirements */ > resource_size_t (*align_resource)(struct pci_dev *dev, > const struct resource *res, > @@ -1849,6 +1853,8 @@ int pci_disable_link_state(struct pci_dev *pdev, int state); > int pci_disable_link_state_locked(struct pci_dev *pdev, int state); > int pci_enable_link_state(struct pci_dev *pdev, int state); > int pci_enable_link_state_locked(struct pci_dev *pdev, int state); > +void pci_host_set_default_pcie_link_state(struct pci_host_bridge *host, > + unsigned int state); > void pcie_no_aspm(void); > bool pcie_aspm_support_enabled(void); > bool pcie_aspm_enabled(struct pci_dev *pdev); > @@ -1861,6 +1867,9 @@ static inline int pci_enable_link_state(struct pci_dev *pdev, int state) > { return 0; } > static inline int pci_enable_link_state_locked(struct pci_dev *pdev, int state) > { return 0; } > +static inline void > +pci_host_set_default_pcie_link_state(struct pci_host_bridge *host, > + unsigned int state) { } > static inline void pcie_no_aspm(void) { } > static inline bool pcie_aspm_support_enabled(void) { return false; } > static inline bool pcie_aspm_enabled(struct pci_dev *pdev) { return false; } > > base-commit: c17b750b3ad9f45f2b6f7e6f7f4679844244f0b9 -- Kenneth R. Crudup / Sr. SW Engineer, Scott County Consulting, Orange County CA