Re: [PATCH v15 3/9] PCI: Add new array for keeping track of ordering of reset methods

[Raphael Norwitz <raphael.norwitz@nutanix.com>]

On Thu, Aug 05, 2021 at 09:59:11PM +0530, Amey Narkhede wrote:
> Introduce a new array reset_methods in struct pci_dev to keep track of
> reset mechanisms supported by the device and their ordering.
> 
> Also refactor probing and reset functions to take advantage of calling
> convention of reset functions.
> 
> Co-developed-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Amey Narkhede <ameynarkhede03@gmail.com>

Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>

> ---
>  drivers/pci/pci.c   | 95 ++++++++++++++++++++++++++-------------------
>  drivers/pci/pci.h   |  8 +++-
>  drivers/pci/probe.c |  5 +--
>  include/linux/pci.h |  7 ++++
>  4 files changed, 71 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 7d1d9671160b..67eab3d29cb3 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -73,6 +73,11 @@ static void pci_dev_d3_sleep(struct pci_dev *dev)
>  		msleep(delay);
>  }
>  
> +bool pci_reset_supported(struct pci_dev *dev)
> +{
> +	return dev->reset_methods[0] != 0;
> +}
> +
>  #ifdef CONFIG_PCI_DOMAINS
>  int pci_domains_supported = 1;
>  #endif
> @@ -5117,6 +5122,16 @@ static void pci_dev_restore(struct pci_dev *dev)
>  		err_handler->reset_done(dev);
>  }
>  
> +/* dev->reset_methods[] is a 0-terminated list of indices into this array */
> +static const struct pci_reset_fn_method pci_reset_fn_methods[] = {
> +	{ },
> +	{ pci_dev_specific_reset, .name = "device_specific" },
> +	{ pcie_reset_flr, .name = "flr" },
> +	{ pci_af_flr, .name = "af_flr" },
> +	{ pci_pm_reset, .name = "pm" },
> +	{ pci_reset_bus_function, .name = "bus" },
> +};
> +
>  /**
>   * __pci_reset_function_locked - reset a PCI device function while holding
>   * the @dev mutex lock.
> @@ -5139,65 +5154,65 @@ static void pci_dev_restore(struct pci_dev *dev)
>   */
>  int __pci_reset_function_locked(struct pci_dev *dev)
>  {
> -	int rc;
> +	int i, m, rc = -ENOTTY;
>  
>  	might_sleep();
>  
>  	/*
> -	 * A reset method returns -ENOTTY if it doesn't support this device
> -	 * and we should try the next method.
> +	 * A reset method returns -ENOTTY if it doesn't support this device and
> +	 * we should try the next method.
>  	 *
> -	 * If it returns 0 (success), we're finished.  If it returns any
> -	 * other error, we're also finished: this indicates that further
> -	 * reset mechanisms might be broken on the device.
> +	 * If it returns 0 (success), we're finished.  If it returns any other
> +	 * error, we're also finished: this indicates that further reset
> +	 * mechanisms might be broken on the device.
>  	 */
> -	rc = pci_dev_specific_reset(dev, 0);
> -	if (rc != -ENOTTY)
> -		return rc;
> -	rc = pcie_reset_flr(dev, 0);
> -	if (rc != -ENOTTY)
> -		return rc;
> -	rc = pci_af_flr(dev, 0);
> -	if (rc != -ENOTTY)
> -		return rc;
> -	rc = pci_pm_reset(dev, 0);
> -	if (rc != -ENOTTY)
> -		return rc;
> -	return pci_reset_bus_function(dev, 0);
> +	for (i = 0; i <  PCI_NUM_RESET_METHODS; i++) {
> +		m = dev->reset_methods[i];
> +		if (!m)
> +			return -ENOTTY;
> +
> +		rc = pci_reset_fn_methods[m].reset_fn(dev, 0);
> +		if (!rc)
> +			return 0;
> +		if (rc != -ENOTTY)
> +			return rc;
> +	}
> +
> +	return -ENOTTY;
>  }
>  EXPORT_SYMBOL_GPL(__pci_reset_function_locked);
>  
>  /**
> - * pci_probe_reset_function - check whether the device can be safely reset
> - * @dev: PCI device to reset
> + * pci_init_reset_methods - check whether device can be safely reset
> + * and store supported reset mechanisms.
> + * @dev: PCI device to check for reset mechanisms
>   *
>   * Some devices allow an individual function to be reset without affecting
> - * other functions in the same device.  The PCI device must be responsive
> - * to PCI config space in order to use this function.
> + * other functions in the same device.  The PCI device must be in D0-D3hot
> + * state.
>   *
> - * Returns 0 if the device function can be reset or negative if the
> - * device doesn't support resetting a single function.
> + * Stores reset mechanisms supported by device in reset_methods byte array
> + * which is a member of struct pci_dev.
>   */
> -int pci_probe_reset_function(struct pci_dev *dev)
> +void pci_init_reset_methods(struct pci_dev *dev)
>  {
> -	int rc;
> +	int m, i, rc;
> +
> +	BUILD_BUG_ON(ARRAY_SIZE(pci_reset_fn_methods) != PCI_NUM_RESET_METHODS);
>  
>  	might_sleep();
>  
> -	rc = pci_dev_specific_reset(dev, 1);
> -	if (rc != -ENOTTY)
> -		return rc;
> -	rc = pcie_reset_flr(dev, 1);
> -	if (rc != -ENOTTY)
> -		return rc;
> -	rc = pci_af_flr(dev, 1);
> -	if (rc != -ENOTTY)
> -		return rc;
> -	rc = pci_pm_reset(dev, 1);
> -	if (rc != -ENOTTY)
> -		return rc;
> +	i = 0;
> +
> +	for (m = 1; m < PCI_NUM_RESET_METHODS; m++) {
> +		rc = pci_reset_fn_methods[m].reset_fn(dev, 1);
> +		if (!rc)
> +			dev->reset_methods[i++] = m;
> +		else if (rc != -ENOTTY)
> +			break;
> +	}
>  
> -	return pci_reset_bus_function(dev, 1);
> +	dev->reset_methods[i] = 0;
>  }
>  
>  /**
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 37c913bbc6e1..7438953745e0 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -33,7 +33,8 @@ enum pci_mmap_api {
>  int pci_mmap_fits(struct pci_dev *pdev, int resno, struct vm_area_struct *vmai,
>  		  enum pci_mmap_api mmap_api);
>  
> -int pci_probe_reset_function(struct pci_dev *dev);
> +bool pci_reset_supported(struct pci_dev *dev);
> +void pci_init_reset_methods(struct pci_dev *dev);
>  int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
>  int pci_bus_error_reset(struct pci_dev *dev);
>  
> @@ -606,6 +607,11 @@ struct pci_dev_reset_methods {
>  	int (*reset)(struct pci_dev *dev, int probe);
>  };
>  
> +struct pci_reset_fn_method {
> +	int (*reset_fn)(struct pci_dev *pdev, int probe);
> +	char *name;
> +};
> +
>  #ifdef CONFIG_PCI_QUIRKS
>  int pci_dev_specific_reset(struct pci_dev *dev, int probe);
>  #else
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index df3f9db6e151..5d8ad230f7d0 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2405,9 +2405,8 @@ static void pci_init_capabilities(struct pci_dev *dev)
>  	pci_rcec_init(dev);		/* Root Complex Event Collector */
>  
>  	pcie_report_downtraining(dev);
> -
> -	if (pci_probe_reset_function(dev) == 0)
> -		dev->reset_fn = 1;
> +	pci_init_reset_methods(dev);
> +	dev->reset_fn = pci_reset_supported(dev);
>  }
>  
>  /*
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index aa85e7d3147e..d1a9a232d08e 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -49,6 +49,9 @@
>  			       PCI_STATUS_SIG_TARGET_ABORT | \
>  			       PCI_STATUS_PARITY)
>  
> +/* Number of reset methods used in pci_reset_fn_methods array in pci.c */
> +#define PCI_NUM_RESET_METHODS 6
> +
>  /*
>   * The PCI interface treats multi-function devices as independent
>   * devices.  The slot/function address of each device is encoded
> @@ -506,6 +509,10 @@ struct pci_dev {
>  	char		*driver_override; /* Driver name to force a match */
>  
>  	unsigned long	priv_flags;	/* Private flags for the PCI driver */
> +	/*
> +	 * See pci_reset_fn_methods array in pci.c for ordering.
> +	 */
> +	u8 reset_methods[PCI_NUM_RESET_METHODS];	/* Reset methods ordered by priority */
>  };
>  
>  static inline struct pci_dev *pci_physfn(struct pci_dev *dev)
> -- 
> 2.32.0
> 
>