linux-kernel - Re: [PATCH v8 1/3] PCI: Add helper to check if any of ancestor device support D3cold

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Date: Wed, 17 Apr 2024 18:15:51 -0700
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
To: Kai-Heng Feng <kai.heng.feng@...onical.com>, bhelgaas@...gle.com
Cc: mahesh@...ux.ibm.com, oohall@...il.com, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
 bagasdotme@...il.com, regressions@...ts.linux.dev,
 linux-nvme@...ts.infradead.org, kch@...dia.com, hch@....de,
 gloriouseggroll@...il.com, kbusch@...nel.org, sagi@...mberg.me, hare@...e.de
Subject: Re: [PATCH v8 1/3] PCI: Add helper to check if any of ancestor device
 support D3cold


On 4/15/24 9:32 PM, Kai-Heng Feng wrote:
> In addition to nearest upstream bridge, driver may want to know if the
> entire hierarchy can be powered off to perform different action.
>
> So walk higher up the hierarchy to find out if any device has valid
> _PR3.
>
> The user will be introduced in next patch.
>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---

Since it has been a while, I was not sure what this series is about.

IMO, it is better to include a cover letter with the summary of your
changes.


> v8:
>  - No change.
>
>  drivers/pci/pci.c   | 16 ++++++++++++++++
>  include/linux/pci.h |  2 ++
>  2 files changed, 18 insertions(+)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index e5f243dd4288..7a5662f116b8 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -6225,6 +6225,22 @@ bool pci_pr3_present(struct pci_dev *pdev)
>  		acpi_has_method(adev->handle, "_PR3");
>  }
>  EXPORT_SYMBOL_GPL(pci_pr3_present);
> +
> +bool pci_ancestor_pr3_present(struct pci_dev *pdev)
> +{
> +	struct pci_dev *parent = pdev;
> +
> +	if (acpi_disabled)
> +		return false;
> +
> +	while ((parent = pci_upstream_bridge(parent))) {
> +		if (pci_pr3_present(pdev))

I think it should be "parent" here?

> +			return true;
> +	}
> +
> +	return false;
> +}
> +EXPORT_SYMBOL_GPL(pci_ancestor_pr3_present);
>  #endif
>  
>  /**
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 16493426a04f..cd71ebfd0f89 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -2620,10 +2620,12 @@ struct irq_domain *pci_host_bridge_acpi_msi_domain(struct pci_bus *bus);
>  void
>  pci_msi_register_fwnode_provider(struct fwnode_handle *(*fn)(struct device *));
>  bool pci_pr3_present(struct pci_dev *pdev);
> +bool pci_ancestor_pr3_present(struct pci_dev *pdev);
>  #else
>  static inline struct irq_domain *
>  pci_host_bridge_acpi_msi_domain(struct pci_bus *bus) { return NULL; }
>  static inline bool pci_pr3_present(struct pci_dev *pdev) { return false; }
> +static inline bool pci_ancestor_pr3_present(struct pci_dev *pdev) { return false; }
>  #endif
>  
>  #ifdef CONFIG_EEH

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer