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Message-ID: <7deae6e0-44ad-4b2c-9657-e83ffc77b4f7@oss.qualcomm.com>
Date: Mon, 25 Aug 2025 09:56:41 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: manivannan.sadhasivam@....qualcomm.com,
Manivannan Sadhasivam <mani@...nel.org>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Krzysztof Wilczyński <kwilczynski@...nel.org>,
Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>
Cc: linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org,
"David E. Box" <david.e.box@...ux.intel.com>,
Johan Hovold <johan@...nel.org>, stable+noautosel@...nel.org
Subject: Re: [PATCH v2] PCI: qcom: Use pci_host_set_default_pcie_link_state()
API to enable ASPM for all platforms
On 8/23/2025 11:14 PM, Manivannan Sadhasivam via B4 Relay wrote:
> From: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
>
> Commit 9f4f3dfad8cf ("PCI: qcom: Enable ASPM for platforms supporting 1.9.0
> ops") allowed the Qcom controller driver to enable ASPM for all PCI devices
> enumerated at the time of the controller driver probe. It proved to be
> useful for devices already powered on by the bootloader, as it allowed
> devices to enter ASPM without user intervention.
>
> However, it could not enable ASPM for the hotplug capable devices i.e.,
> devices enumerated *after* the controller driver probe. This limitation
> mostly went unnoticed as the Qcom PCI controllers are not hotplug capable
> and also the bootloader has been enabling the PCI devices before Linux
> Kernel boots (mostly on the Qcom compute platforms which users use on a
> daily basis).
>
> But with the advent of the commit b458ff7e8176 ("PCI/pwrctl: Ensure that
> pwrctl drivers are probed before PCI client drivers"), the pwrctrl driver
> started to block the PCI device enumeration until it had been probed.
> Though, the intention of the commit was to avoid race between the pwrctrl
> driver and PCI client driver, it also meant that the pwrctrl controlled PCI
> devices may get probed after the controller driver and will no longer have
> ASPM enabled. So users started noticing high runtime power consumption with
> WLAN chipsets on Qcom compute platforms like Thinkpad X13s, and Thinkpad
> T14s, etc...
>
> Obviously, it is the pwrctrl change that caused regression, but it
> ultimately uncovered a flaw in the ASPM enablement logic of the controller
> driver. So to address the actual issue, use the newly introduced
> pci_host_set_default_pcie_link_state() API, which allows the controller
> drivers to set the default ASPM state for *all* devices. This default state
> will be honored by the ASPM driver while enabling ASPM for all the devices.
>
> So with this change, we can get rid of the controller driver specific
> 'qcom_pcie_ops::host_post_init' callback.
>
> Also with this change, ASPM is now enabled by default on all Qcom
> platforms as I haven't heard of any reported issues (apart from the
> unsupported L0s on some platorms, which is still handled separately).
>
> Cc: stable+noautosel@...nel.org # API dependency
> Fixes: 9f4f3dfad8cf ("PCI: qcom: Enable ASPM for platforms supporting 1.9.0 ops")
> Reported-by: Johan Hovold <johan@...nel.org>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> ---
> Changes in v2:
>
> * Used the new API introduced in this patch instead of bus notifier:
> https://lore.kernel.org/linux-pci/20250822031159.4005529-1-david.e.box@linux.intel.com/
>
> * Enabled ASPM on all platforms as there is no specific reason to limit it to a
> few.
> ---
> drivers/pci/controller/dwc/pcie-qcom.c | 34 ++--------------------------------
> 1 file changed, 2 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 294babe1816e4d0c2b2343fe22d89af72afcd6cd..71f14bc3a06ade1da1374e88b0ebef8c4e266064 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -247,7 +247,6 @@ struct qcom_pcie_ops {
> int (*get_resources)(struct qcom_pcie *pcie);
> int (*init)(struct qcom_pcie *pcie);
> int (*post_init)(struct qcom_pcie *pcie);
> - void (*host_post_init)(struct qcom_pcie *pcie);
> void (*deinit)(struct qcom_pcie *pcie);
> void (*ltssm_enable)(struct qcom_pcie *pcie);
> int (*config_sid)(struct qcom_pcie *pcie);
> @@ -1040,25 +1039,6 @@ static int qcom_pcie_post_init_2_7_0(struct qcom_pcie *pcie)
> return 0;
> }
>
> -static int qcom_pcie_enable_aspm(struct pci_dev *pdev, void *userdata)
> -{
> - /*
> - * Downstream devices need to be in D0 state before enabling PCI PM
> - * substates.
> - */
> - pci_set_power_state_locked(pdev, PCI_D0);
> - pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
> -
> - return 0;
> -}
> -
> -static void qcom_pcie_host_post_init_2_7_0(struct qcom_pcie *pcie)
> -{
> - struct dw_pcie_rp *pp = &pcie->pci->pp;
> -
> - pci_walk_bus(pp->bridge->bus, qcom_pcie_enable_aspm, NULL);
> -}
> -
> static void qcom_pcie_deinit_2_7_0(struct qcom_pcie *pcie)
> {
> struct qcom_pcie_resources_2_7_0 *res = &pcie->res.v2_7_0;
> @@ -1358,19 +1338,9 @@ static void qcom_pcie_host_deinit(struct dw_pcie_rp *pp)
> pcie->cfg->ops->deinit(pcie);
> }
>
> -static void qcom_pcie_host_post_init(struct dw_pcie_rp *pp)
> -{
> - struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> - struct qcom_pcie *pcie = to_qcom_pcie(pci);
> -
> - if (pcie->cfg->ops->host_post_init)
> - pcie->cfg->ops->host_post_init(pcie);
> -}
> -
> static const struct dw_pcie_host_ops qcom_pcie_dw_ops = {
> .init = qcom_pcie_host_init,
> .deinit = qcom_pcie_host_deinit,
> - .post_init = qcom_pcie_host_post_init,
> };
>
> /* Qcom IP rev.: 2.1.0 Synopsys IP rev.: 4.01a */
> @@ -1432,7 +1402,6 @@ static const struct qcom_pcie_ops ops_1_9_0 = {
> .get_resources = qcom_pcie_get_resources_2_7_0,
> .init = qcom_pcie_init_2_7_0,
> .post_init = qcom_pcie_post_init_2_7_0,
> - .host_post_init = qcom_pcie_host_post_init_2_7_0,
> .deinit = qcom_pcie_deinit_2_7_0,
> .ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
> .config_sid = qcom_pcie_config_sid_1_9_0,
> @@ -1443,7 +1412,6 @@ static const struct qcom_pcie_ops ops_1_21_0 = {
> .get_resources = qcom_pcie_get_resources_2_7_0,
> .init = qcom_pcie_init_2_7_0,
> .post_init = qcom_pcie_post_init_2_7_0,
> - .host_post_init = qcom_pcie_host_post_init_2_7_0,
> .deinit = qcom_pcie_deinit_2_7_0,
> .ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
> };
> @@ -1979,6 +1947,8 @@ static int qcom_pcie_probe(struct platform_device *pdev)
> if (pcie->mhi)
> qcom_pcie_init_debugfs(pcie);
>
> + pci_host_set_default_pcie_link_state(pp->bridge, PCIE_LINK_STATE_ALL);
> +
It is better to call this before starting link training, if the endpoint
is already powered on by the time execution comes here link enumeration
and ASPM init might be already done. This might not have any impact.
- Krishna Chaitanya.
> return 0;
>
> err_host_deinit:
>
> ---
> base-commit: 681accdad91923ef4938b96ff3eea62e29af74c3
> change-id: 20250823-qcom_aspm_fix-3264926b5b14
>
> Best regards,
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