linux-kernel - Re: [PATCH v2 6/6] PCI/PORTDRV: Remove ERR_FATAL handling from pcie_portdrv_slot

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Message-ID: <20180718191024.GE128988@bhelgaas-glaptop.roam.corp.google.com>
Date:   Wed, 18 Jul 2018 14:10:24 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Oza Pawandeep <poza@...eaurora.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dongdong Liu <liudongdong3@...wei.com>,
        Keith Busch <keith.busch@...el.com>, Wei Zhang <wzhang@...com>,
        Sinan Kaya <okaya@...eaurora.org>,
        Timur Tabi <timur@...eaurora.org>
Subject: Re: [PATCH v2 6/6] PCI/PORTDRV: Remove ERR_FATAL handling from
 pcie_portdrv_slot_reset()

On Fri, Jun 22, 2018 at 05:58:14AM -0400, Oza Pawandeep wrote:
> We are handling ERR_FATAL by resetting the Link in software,skipping the
> driver pci_error_handlers callbacks, removing the devices from the PCI
> subsystem, and re-enumerating, because of, no need to handle
> pci_channel_io_frozen case anymore.
> 
> Besides the walk on the bus is happening on subordinates, inside
> broadcast_error_message(), which means that pcie_portdrv_slot_reset()
> is never called for RP, and now since the all the devices are removed under
> this downstream link, we can safely get rid of ERR_FATAL handling code
> in pcie_portdrv_slot_reset().

portdrv only binds to bridges, and it looks like
broadcast_error_message() only calls the pci_error_handlers callbacks
for subordinate devices, never for the bridge itself:

  broadcast_error_message
    if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE)
      pci_walk_bus(dev->subordinate, ...)

If that's the case, why do we need pcie_portdrv_err_handler at all?
We should remove it completely if we don't need it.

ISTR some arcane call path for pcie_portdrv_err_resume(), but I don't
remember the details.

> Signed-off-by: Oza Pawandeep <poza@...eaurora.org>
> 
> diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
> index 973f1b8..b970a6d 100644
> --- a/drivers/pci/pcie/portdrv_pci.c
> +++ b/drivers/pci/pcie/portdrv_pci.c
> @@ -42,17 +42,6 @@ __setup("pcie_ports=", pcie_port_setup);
>  
>  /* global data */
>  
> -static int pcie_portdrv_restore_config(struct pci_dev *dev)
> -{
> -	int retval;
> -
> -	retval = pci_enable_device(dev);
> -	if (retval)
> -		return retval;
> -	pci_set_master(dev);
> -	return 0;
> -}
> -
>  #ifdef CONFIG_PM
>  static int pcie_port_runtime_suspend(struct device *dev)
>  {
> @@ -163,13 +152,6 @@ static pci_ers_result_t pcie_portdrv_mmio_enabled(struct pci_dev *dev)
>  static pci_ers_result_t pcie_portdrv_slot_reset(struct pci_dev *dev)
>  {
>  	/* If fatal, restore cfg space for possible link reset at upstream */
> -	if (dev->error_state == pci_channel_io_frozen) {
> -		dev->state_saved = true;
> -		pci_restore_state(dev);
> -		pcie_portdrv_restore_config(dev);
> -		pci_enable_pcie_error_reporting(dev);
> -	}
> -
>  	return PCI_ERS_RESULT_RECOVERED;
>  }
>  
> -- 
> 2.7.4
>