linux-kernel - Re: [PATCH 3/4] PCI: Remove reset_fn field from pci

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Date:   Mon, 15 Mar 2021 00:52:48 +0100
From:   Pali Rohár <pali@...nel.org>
To:     ameynarkhede03@...il.com
Cc:     bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, alex.williamson@...hat.com,
        raphael.norwitz@...anix.com
Subject: Re: [PATCH 3/4] PCI: Remove reset_fn field from pci_dev

On Friday 12 March 2021 23:04:51 ameynarkhede03@...il.com wrote:
> From: Amey Narkhede <ameynarkhede03@...il.com>
> 
> reset_fn field is used to indicate whether the
> device supports any reset mechanism or not.
> Deprecate use of reset_fn in favor of new
> reset_methods bitmap which can be used to keep
> track of all supported reset mechanisms of a device.

Hello Amey!

You cannot trigger PCIe Hot Reset (PCI secondary bus reset) in this
simple way from sysfs via new reset methods.

I proposed very similar functionality just few days ago:
https://lore.kernel.org/linux-pci/20210301171221.3d42a55i7h5ubqsb@pali/T/#u

And I realized that it needs more steps to be done.

At least some remove-reset-rescan procedure done atomically is required.

> Signed-off-by: Amey Narkhede <ameynarkhede03@...il.com>
> ---
> Reviewed-by: Alex Williamson <alex.williamson@...hat.com>
> Reviewed-by: Raphael Norwitz <raphael.norwitz@...anix.com>
> 
>  drivers/net/ethernet/cavium/liquidio/lio_vf_main.c | 2 +-
>  drivers/pci/pci-sysfs.c                            | 6 ++----
>  drivers/pci/pci.c                                  | 6 +++---
>  drivers/pci/probe.c                                | 1 -
>  drivers/pci/quirks.c                               | 2 +-
>  include/linux/pci.h                                | 1 -
>  6 files changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cavium/liquidio/lio_vf_main.c b/drivers/net/ethernet/cavium/liquidio/lio_vf_main.c
> index 9b9d305c6..3e2c49e08 100644
> --- a/drivers/net/ethernet/cavium/liquidio/lio_vf_main.c
> +++ b/drivers/net/ethernet/cavium/liquidio/lio_vf_main.c
> @@ -526,7 +526,7 @@ static void octeon_destroy_resources(struct octeon_device *oct)
>  			oct->irq_name_storage = NULL;
>  		}
>  		/* Soft reset the octeon device before exiting */
> -		if (oct->pci_dev->reset_fn)
> +		if (oct->pci_dev->reset_methods)
>  			octeon_pci_flr(oct);
>  		else
>  			cn23xx_vf_ask_pf_to_do_flr(oct);
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index f8afd54ca..78d2c130c 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1334,7 +1334,7 @@ static int pci_create_capabilities_sysfs(struct pci_dev *dev)
> 
>  	pcie_vpd_create_sysfs_dev_files(dev);
> 
> -	if (dev->reset_fn) {
> +	if (dev->reset_methods) {
>  		retval = device_create_file(&dev->dev, &dev_attr_reset);
>  		if (retval)
>  			goto error;
> @@ -1417,10 +1417,8 @@ int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev)
>  static void pci_remove_capabilities_sysfs(struct pci_dev *dev)
>  {
>  	pcie_vpd_remove_sysfs_dev_files(dev);
> -	if (dev->reset_fn) {
> +	if (dev->reset_methods)
>  		device_remove_file(&dev->dev, &dev_attr_reset);
> -		dev->reset_fn = 0;
> -	}
>  }
> 
>  /**
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 407b44e85..b7f6c6588 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -5175,7 +5175,7 @@ int pci_reset_function(struct pci_dev *dev)
>  {
>  	int rc;
> 
> -	if (!dev->reset_fn)
> +	if (!dev->reset_methods)
>  		return -ENOTTY;
> 
>  	pci_dev_lock(dev);
> @@ -5211,7 +5211,7 @@ int pci_reset_function_locked(struct pci_dev *dev)
>  {
>  	int rc;
> 
> -	if (!dev->reset_fn)
> +	if (!dev->reset_methods)
>  		return -ENOTTY;
> 
>  	pci_dev_save_and_disable(dev);
> @@ -5234,7 +5234,7 @@ int pci_try_reset_function(struct pci_dev *dev)
>  {
>  	int rc;
> 
> -	if (!dev->reset_fn)
> +	if (!dev->reset_methods)
>  		return -ENOTTY;
> 
>  	if (!pci_dev_trylock(dev))
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 01dd037bd..4764e031a 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2404,7 +2404,6 @@ static void pci_init_capabilities(struct pci_dev *dev)
> 
>  	pcie_report_downtraining(dev);
>  	pci_init_reset_methods(dev);
> -	dev->reset_fn = !!dev->reset_methods;
>  }
> 
>  /*
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 0a3df84c9..20a81b1bc 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -5535,7 +5535,7 @@ static void quirk_reset_lenovo_thinkpad_p50_nvgpu(struct pci_dev *pdev)
> 
>  	if (pdev->subsystem_vendor != PCI_VENDOR_ID_LENOVO ||
>  	    pdev->subsystem_device != 0x222e ||
> -	    !pdev->reset_fn)
> +	    !pdev->reset_methods)
>  		return;
> 
>  	if (pci_enable_device_mem(pdev))
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 56d6e4750..a2f003f4e 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -437,7 +437,6 @@ struct pci_dev {
>  	unsigned int	state_saved:1;
>  	unsigned int	is_physfn:1;
>  	unsigned int	is_virtfn:1;
> -	unsigned int	reset_fn:1;
>  	unsigned int	is_hotplug_bridge:1;
>  	unsigned int	shpc_managed:1;		/* SHPC owned by shpchp */
>  	unsigned int	is_thunderbolt:1;	/* Thunderbolt controller */
> --
> 2.30.2