linux-kernel - Re: [PATCH v2 2/3] PCI/DPC: Remove CONFIG_PCIE

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Message-ID: <35cafc72-89d2-48d3-ab73-0af4ed2bcac1@linux.intel.com>
Date: Sun, 25 Feb 2024 12:05:12 -0800
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
To: Bjorn Helgaas <helgaas@...nel.org>, linux-pci@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Matthew W Carlis <mattc@...estorage.com>,
 Keith Busch <kbusch@...nel.org>, Lukas Wunner <lukas@...ner.de>,
 Mika Westerberg <mika.westerberg@...ux.intel.com>,
 Jesse Brandeburg <jesse.brandeburg@...el.com>,
 Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH v2 2/3] PCI/DPC: Remove CONFIG_PCIE_EDR

Hi Bjorn,

On 2/22/24 2:15 PM, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@...gle.com>
>
> Previous Kconfig allowed the possibility of enabling CONFIG_PCIE_DPC
> without CONFIG_PCIE_EDR.  The PCI Firmware Spec, r3.3, sec 4.5.1,
> table 4-5, says an ACPI OS that requests control of DPC must also
> advertise support for EDR.
>
> Remove CONFIG_PCIE_EDR and enable the EDR code with CONFIG_PCIE_DPC so that
> enabling DPC also enables EDR for ACPI systems.  Since EDR is an ACPI
> feature, build edr.o only when CONFIG_ACPI is enabled.  Stubs cover the
> case when DPC is enabled without ACPI.
>
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> ---
>  drivers/acpi/pci_root.c   |  2 +-
>  drivers/pci/pcie/Kconfig  | 14 ++++----------
>  drivers/pci/pcie/Makefile |  5 ++++-
>  drivers/pci/pcie/dpc.c    | 10 ----------
>  include/linux/pci-acpi.h  |  4 ++--
>  5 files changed, 11 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index efc292b6214e..bcaf3d3a5e05 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -448,7 +448,7 @@ static u32 calculate_support(void)
>  		support |= OSC_PCI_ASPM_SUPPORT | OSC_PCI_CLOCK_PM_SUPPORT;
>  	if (pci_msi_enabled())
>  		support |= OSC_PCI_MSI_SUPPORT;
> -	if (IS_ENABLED(CONFIG_PCIE_EDR))
> +	if (IS_ENABLED(CONFIG_PCIE_DPC))	/* DPC => EDR support */
>  		support |= OSC_PCI_EDR_SUPPORT;

Since EDR internally touches AER registers, I still think we should make sure
OS enables AER support before advertising the EDR support.

>  
>  	return support;
> diff --git a/drivers/pci/pcie/Kconfig b/drivers/pci/pcie/Kconfig
> index 8999fcebde6a..21e98289fbe9 100644
> --- a/drivers/pci/pcie/Kconfig
> +++ b/drivers/pci/pcie/Kconfig
> @@ -137,6 +137,10 @@ config PCIE_DPC
>  	  have this capability or you do not want to use this feature,
>  	  it is safe to answer N.
>  
> +	  On ACPI systems, this includes Error Disconnect Recover support,
> +	  the hybrid model that uses both firmware and OS to implement DPC,
> +	  as specified in the PCI Firmware Specification r3.3.

Nit: Include some section reference?

> +
>  config PCIE_PTM
>  	bool "PCI Express Precision Time Measurement support"
>  	help
> @@ -145,13 +149,3 @@ config PCIE_PTM
>  
>  	  This is only useful if you have devices that support PTM, but it
>  	  is safe to enable even if you don't.
> -
> -config PCIE_EDR
> -	bool "PCI Express Error Disconnect Recover support"
> -	depends on PCIE_DPC && ACPI
> -	help
> -	  This option adds Error Disconnect Recover support as specified
> -	  in the Downstream Port Containment Related Enhancements ECN to
> -	  the PCI Firmware Specification r3.2.  Enable this if you want to
> -	  support hybrid DPC model which uses both firmware and OS to
> -	  implement DPC.
> diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
> index 8de4ed5f98f1..72657f780c33 100644
> --- a/drivers/pci/pcie/Makefile
> +++ b/drivers/pci/pcie/Makefile
> @@ -12,4 +12,7 @@ obj-$(CONFIG_PCIEAER_INJECT)	+= aer_inject.o
>  obj-$(CONFIG_PCIE_PME)		+= pme.o
>  obj-$(CONFIG_PCIE_DPC)		+= dpc.o
>  obj-$(CONFIG_PCIE_PTM)		+= ptm.o
> -obj-$(CONFIG_PCIE_EDR)		+= edr.o
> +
> +ifdef CONFIG_ACPI
> +obj-$(CONFIG_PCIE_DPC)		+= edr.o
> +endif
> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> index 94111e438241..0aa79581250b 100644
> --- a/drivers/pci/pcie/dpc.c
> +++ b/drivers/pci/pcie/dpc.c
> @@ -102,19 +102,9 @@ static bool dpc_completed(struct pci_dev *pdev)
>   */
>  bool pci_dpc_recovered(struct pci_dev *pdev)
>  {
> -	struct pci_host_bridge *host;
> -
>  	if (!pdev->dpc_cap)
>  		return false;
>  
> -	/*
> -	 * Synchronization between hotplug and DPC is not supported
> -	 * if DPC is owned by firmware and EDR is not enabled.
> -	 */
> -	host = pci_find_host_bridge(pdev->bus);
> -	if (!host->native_dpc && !IS_ENABLED(CONFIG_PCIE_EDR))
> -		return false;
> -
>  	/*
>  	 * Need a timeout in case DPC never completes due to failure of
>  	 * dpc_wait_rp_inactive().  The spec doesn't mandate a time limit,
> diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
> index 078225b514d4..92e196ba0249 100644
> --- a/include/linux/pci-acpi.h
> +++ b/include/linux/pci-acpi.h
> @@ -122,13 +122,13 @@ extern const guid_t pci_acpi_dsm_guid;
>  #define DSM_PCI_POWER_ON_RESET_DELAY		0x08
>  #define DSM_PCI_DEVICE_READINESS_DURATIONS	0x09
>  
> -#ifdef CONFIG_PCIE_EDR
> +#ifdef CONFIG_PCIE_DPC
>  void pci_acpi_add_edr_notifier(struct pci_dev *pdev);
>  void pci_acpi_remove_edr_notifier(struct pci_dev *pdev);
>  #else
>  static inline void pci_acpi_add_edr_notifier(struct pci_dev *pdev) { }
>  static inline void pci_acpi_remove_edr_notifier(struct pci_dev *pdev) { }
> -#endif /* CONFIG_PCIE_EDR */
> +#endif /* CONFIG_PCIE_DPC */
>  
>  int pci_acpi_set_companion_lookup_hook(struct acpi_device *(*func)(struct pci_dev *));
>  void pci_acpi_clear_companion_lookup_hook(void);

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer