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Message-ID: <84ce803d-b9b6-0ae7-44fa-c793dca06421@linux.intel.com>
Date: Mon, 12 May 2025 14:50:01 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Shawn Anastasio <sanastasio@...torengineering.com>
cc: linux-pci@...r.kernel.org, Lukas Wunner <lukas@...ner.de>,
Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Krzysztof Wilczyński <kw@...ux.com>,
Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
Rob Herring <robh@...nel.o>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>,
chaitanya chundru <quic_krichai@...cinc.com>,
Bjorn Andersson <andersson@...nel.org>,
Konrad Dybcio <konradybcio@...nel.org>,
cros-qcom-dts-watchers@...omium.org, Jingoo Han <jingoohan1@...il.com>,
Bartosz Golaszewski <brgl@...ev.pl>, quic_vbadigan@...cnic.com,
amitk@...nel.org, devicetree@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>, linux-arm-msm@...r.kernel.org,
jorge.ramirez@....qualcomm.com, Dmitry Baryshkov <lumag@...nel.org>,
Timothy Pearson <tpearson@...torengineering.com>
Subject: Re: [RESEND PATCH v6] PCI: PCI: Add pcie_link_is_active() to determine
if the PCIe link is active
On Fri, 9 May 2025, Shawn Anastasio wrote:
In shortlog:
PCI: PCI: ... -> PCI: ...
> From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
>
> Date: Sat, 12 Apr 2025 07:19:56 +0530
>
> Introduce a common API to check if the PCIe link is active, replacing
> duplicate code in multiple locations.
>
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> Signed-off-by: Shawn Anastasio <sanastasio@...torengineering.com>
> ---
> (Resent since git-send-email failed to detect the Subject field from the patch
> file previously -- apologies!)
>
> This is an updated patch pulled from Krishna's v5 series:
> https://patchwork.kernel.org/project/linux-pci/list/?series=952665
>
> The following changes to Krishna's v5 were made by me:
> - Revert pcie_link_is_active return type back to int per Lukas' review
> comments
> - Handle non-zero error returns at call site of the new function in
> pci.c/pci_bridge_wait_for_secondary_bus
>
> drivers/pci/hotplug/pciehp.h | 1 -
> drivers/pci/hotplug/pciehp_ctrl.c | 2 +-
> drivers/pci/hotplug/pciehp_hpc.c | 33 +++----------------------------
> drivers/pci/pci.c | 26 +++++++++++++++++++++---
> include/linux/pci.h | 4 ++++
> 5 files changed, 31 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
> index 273dd8c66f4e..acef728530e3 100644
> --- a/drivers/pci/hotplug/pciehp.h
> +++ b/drivers/pci/hotplug/pciehp.h
> @@ -186,7 +186,6 @@ int pciehp_query_power_fault(struct controller *ctrl);
> int pciehp_card_present(struct controller *ctrl);
> int pciehp_card_present_or_link_active(struct controller *ctrl);
> int pciehp_check_link_status(struct controller *ctrl);
> -int pciehp_check_link_active(struct controller *ctrl);
> void pciehp_release_ctrl(struct controller *ctrl);
>
> int pciehp_sysfs_enable_slot(struct hotplug_slot *hotplug_slot);
> diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
> index d603a7aa7483..4bb58ba1c766 100644
> --- a/drivers/pci/hotplug/pciehp_ctrl.c
> +++ b/drivers/pci/hotplug/pciehp_ctrl.c
> @@ -260,7 +260,7 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
> /* Turn the slot on if it's occupied or link is up */
> mutex_lock(&ctrl->state_lock);
> present = pciehp_card_present(ctrl);
> - link_active = pciehp_check_link_active(ctrl);
> + link_active = pcie_link_is_active(ctrl->pcie->port);
> if (present <= 0 && link_active <= 0) {
> if (ctrl->state == BLINKINGON_STATE) {
> ctrl->state = OFF_STATE;
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 8a09fb6083e2..278bc21d531d 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -221,33 +221,6 @@ static void pcie_write_cmd_nowait(struct controller *ctrl, u16 cmd, u16 mask)
> pcie_do_write_cmd(ctrl, cmd, mask, false);
> }
>
> -/**
> - * pciehp_check_link_active() - Is the link active
> - * @ctrl: PCIe hotplug controller
> - *
> - * Check whether the downstream link is currently active. Note it is
> - * possible that the card is removed immediately after this so the
> - * caller may need to take it into account.
> - *
> - * If the hotplug controller itself is not available anymore returns
> - * %-ENODEV.
> - */
> -int pciehp_check_link_active(struct controller *ctrl)
> -{
> - struct pci_dev *pdev = ctrl_dev(ctrl);
> - u16 lnk_status;
> - int ret;
> -
> - ret = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
> - if (ret == PCIBIOS_DEVICE_NOT_FOUND || PCI_POSSIBLE_ERROR(lnk_status))
> - return -ENODEV;
> -
> - ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
> - ctrl_dbg(ctrl, "%s: lnk_status = %x\n", __func__, lnk_status);
> -
> - return ret;
> -}
> -
> static bool pci_bus_check_dev(struct pci_bus *bus, int devfn)
> {
> u32 l;
> @@ -467,7 +440,7 @@ int pciehp_card_present_or_link_active(struct controller *ctrl)
> if (ret)
> return ret;
>
> - return pciehp_check_link_active(ctrl);
> + return pcie_link_is_active(ctrl_dev(ctrl));
> }
>
> int pciehp_query_power_fault(struct controller *ctrl)
> @@ -584,7 +557,7 @@ static void pciehp_ignore_dpc_link_change(struct controller *ctrl,
> * Synthesize it to ensure that it is acted on.
> */
> down_read_nested(&ctrl->reset_lock, ctrl->depth);
> - if (!pciehp_check_link_active(ctrl))
> + if (!pcie_link_is_active(ctrl_dev(ctrl)))
> pciehp_request(ctrl, PCI_EXP_SLTSTA_DLLSC);
> up_read(&ctrl->reset_lock);
> }
> @@ -884,7 +857,7 @@ int pciehp_slot_reset(struct pcie_device *dev)
> pcie_capability_write_word(dev->port, PCI_EXP_SLTSTA,
> PCI_EXP_SLTSTA_DLLSC);
>
> - if (!pciehp_check_link_active(ctrl))
> + if (!pcie_link_is_active(ctrl_dev(ctrl)))
> pciehp_request(ctrl, PCI_EXP_SLTSTA_DLLSC);
>
> return 0;
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index e77d5b53c0ce..3bb8354b14bf 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4926,7 +4926,6 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type)
> return 0;
>
> if (pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) {
> - u16 status;
>
> pci_dbg(dev, "waiting %d ms for downstream link\n", delay);
> msleep(delay);
> @@ -4942,8 +4941,7 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type)
> if (!dev->link_active_reporting)
> return -ENOTTY;
>
> - pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &status);
> - if (!(status & PCI_EXP_LNKSTA_DLLLA))
> + if (pcie_link_is_active(dev) <= 0)
> return -ENOTTY;
>
> return pci_dev_wait(child, reset_type,
> @@ -6247,6 +6245,28 @@ void pcie_print_link_status(struct pci_dev *dev)
> }
> EXPORT_SYMBOL(pcie_print_link_status);
>
> +/**
> + * pcie_link_is_active() - Checks if the link is active or not
> + * @pdev: PCI device to query
> + *
> + * Check whether the link is active or not.
> + *
> + * Return: link state, or -ENODEV if the config read failes.
"link state" is bit vague, it would be better to document the values
returned more precisely.
> + */
> +int pcie_link_is_active(struct pci_dev *pdev)
> +{
> + u16 lnk_status;
> + int ret;
> +
> + ret = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
> + if (ret == PCIBIOS_DEVICE_NOT_FOUND || PCI_POSSIBLE_ERROR(lnk_status))
> + return -ENODEV;
> +
> + pci_dbg(pdev, "lnk_status = %x\n", lnk_status);
> + return !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
> +}
> +EXPORT_SYMBOL(pcie_link_is_active);
> +
> /**
> * pci_select_bars - Make BAR mask from the type of resource
> * @dev: the PCI device for which BAR mask is made
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 51e2bd6405cd..a79a9919320c 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1945,6 +1945,7 @@ pci_release_mem_regions(struct pci_dev *pdev)
> pci_select_bars(pdev, IORESOURCE_MEM));
> }
>
> +int pcie_link_is_active(struct pci_dev *dev);
Is this really needed in include/linux/pci.h, isn't drivers/pci/pci.h
enough (for pwrctrl in the Krishna's series)?
> #else /* CONFIG_PCI is not enabled */
>
> static inline void pci_set_flags(int flags) { }
> @@ -2093,6 +2094,9 @@ pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
> {
> return -ENOSPC;
> }
> +
> +static inline bool pcie_link_is_active(struct pci_dev *dev)
> +{ return false; }
This fits on one line just fine.
--
i.
> #endif /* CONFIG_PCI */
>
> /* Include architecture-dependent settings and functions */
> --
> 2.30.2
>
>
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