linux-kernel - Re: [PATCH v10 7/8] PCI: Add support for ACPI

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Date:   Mon, 12 Jul 2021 17:09:20 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Shanker Donthineni <sdonthineni@...dia.com>
Cc:     Amey Narkhede <ameynarkhede03@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Raphael Norwitz <raphael.norwitz@...anix.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        kw@...ux.com, Sinan Kaya <okaya@...nel.org>,
        Len Brown <lenb@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v10 7/8] PCI: Add support for ACPI _RST reset method

On Fri,  9 Jul 2021 18:08:12 +0530
Amey Narkhede <ameynarkhede03@...il.com> wrote:

> From: Shanker Donthineni <sdonthineni@...dia.com>
> 
> The _RST is a standard method specified in the ACPI specification. It
> provides a function level reset when it is described in the acpi_device
> context associated with PCI-device. Implement a new reset function
> pci_dev_acpi_reset() for probing RST method and execute if it is defined
> in the firmware.
> 
> The default priority of the ACPI reset is set to below device-specific
> and above hardware resets.
> 
> Signed-off-by: Shanker Donthineni <sdonthineni@...dia.com>
> Suggested-by: Alex Williamson <alex.williamson@...hat.com>
> Reviewed-by: Sinan Kaya <okaya@...nel.org>
> ---
>  drivers/pci/pci-acpi.c | 23 +++++++++++++++++++++++
>  drivers/pci/pci.c      |  1 +
>  drivers/pci/pci.h      |  6 ++++++
>  include/linux/pci.h    |  2 +-
>  4 files changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index dae021322..b6de71d15 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -941,6 +941,29 @@ void pci_set_acpi_fwnode(struct pci_dev *dev)
>  				   acpi_pci_find_companion(&dev->dev));
>  }
>  
> +/**
> + * pci_dev_acpi_reset - do a function level reset using _RST method
> + * @dev: device to reset
> + * @probe: check if _RST method is included in the acpi_device context.
> + */
> +int pci_dev_acpi_reset(struct pci_dev *dev, int probe)
> +{
> +	acpi_handle handle = ACPI_HANDLE(&dev->dev);
> +
> +	if (!handle || !acpi_has_method(handle, "_RST"))
> +		return -ENOTTY;
> +
> +	if (probe)
> +		return 0;
> +
> +	if (ACPI_FAILURE(acpi_evaluate_object(handle, "_RST", NULL, NULL))) {
> +		pci_warn(dev, "ACPI _RST failed\n");
> +		return -EINVAL;


Should we return -ENOTTY here instead to give a possible secondary
reset method a chance?  Thanks,

Alex


> +	}
> +
> +	return 0;
> +}
> +
>  static bool acpi_pci_bridge_d3(struct pci_dev *dev)
>  {
>  	const struct fwnode_handle *fwnode;
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index d5c16492c..1e64dbd3e 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5115,6 +5115,7 @@ static void pci_dev_restore(struct pci_dev *dev)
>  const struct pci_reset_fn_method pci_reset_fn_methods[] = {
>  	{ },
>  	{ &pci_dev_specific_reset, .name = "device_specific" },
> +	{ &pci_dev_acpi_reset, .name = "acpi" },
>  	{ &pcie_reset_flr, .name = "flr" },
>  	{ &pci_af_flr, .name = "af_flr" },
>  	{ &pci_pm_reset, .name = "pm" },
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 990b73e90..2c12017ed 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -705,7 +705,13 @@ static inline int pci_aer_raw_clear_status(struct pci_dev *dev) { return -EINVAL
>  int pci_acpi_program_hp_params(struct pci_dev *dev);
>  extern const struct attribute_group pci_dev_acpi_attr_group;
>  void pci_set_acpi_fwnode(struct pci_dev *dev);
> +int pci_dev_acpi_reset(struct pci_dev *dev, int probe);
>  #else
> +static inline int pci_dev_acpi_reset(struct pci_dev *dev, int probe)
> +{
> +	return -ENOTTY;
> +}
> +
>  static inline void pci_set_acpi_fwnode(struct pci_dev *dev) {}
>  static inline int pci_acpi_program_hp_params(struct pci_dev *dev)
>  {
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index f34563831..c3b0d771c 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -50,7 +50,7 @@
>  			       PCI_STATUS_PARITY)
>  
>  /* Number of reset methods used in pci_reset_fn_methods array in pci.c */
> -#define PCI_NUM_RESET_METHODS 6
> +#define PCI_NUM_RESET_METHODS 7
>  
>  /*
>   * The PCI interface treats multi-function devices as independent