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

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Date:   Fri, 08 Jun 2018 06:41:48 -0400
From:   okaya@...eaurora.org
To:     poza@...eaurora.org
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        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>,
        Timur Tabi <timur@...eaurora.org>,
        linux-pci-owner@...r.kernel.org
Subject: Re: [PATCH NEXT 6/6] PCI/PORTDRV: Remove ERR_FATAL handling from
 pcie_portdrv_slot_reset()

On 2018-06-08 00:57, poza@...eaurora.org wrote:
> On 2018-06-08 03:04, Bjorn Helgaas wrote:
>> On Thu, Jun 07, 2018 at 07:18:03PM +0530, poza@...eaurora.org wrote:
>>> On 2018-06-07 11:30, 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, as a result of that, no more calling
>>> > pcie_portdrv_slot_reset in ERR_FATAL case.
>>> >
>>> > 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..92f5d330 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)
>>> >  {
>>> > @@ -162,14 +151,6 @@ 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;
>>> >  }
>>> 
>>> 
>>> Hi Bjorn,
>>> 
>>> the above patch removes ERR_FATAL handling from 
>>> pcie_portdrv_slot_reset()
>>> because now we are handling ERR_FATAL differently than before.
>>> 
>>> I tried to dig into pcie_portdrv_slot_reset() handling for ERR_FATAL 
>>> case
>>> where it
>>> restores the config space, enable device, set master and enable error
>>> reporting....
>>> and as far as I understand this is being done for upstream link 
>>> (bridges
>>> etc..)
>>> 
>>> why was it done at the first point (I checked the commit description, 
>>> but
>>> could not really get it)
>>> and do we need to handle the same thing in ERR_FATAL now ?
>> 
>> You mean 4bf3392e0bf5 ("PCI-Express AER implemetation: pcie_portdrv
>> error handler"), which added pcie_portdrv_slot_reset()?  I agree, that
>> commit log has no useful information.  I don't know any of the history
>> behind it.
> 
> 
> Yes Bjorn thats right.
> I am trying to understand it but no clue.
> since it is restoring the stuffs in ERR_FATAL case, why would PCIe
> bridge loose all the settings ?  [config space, aer bits, master,
> device enable etc..)
> Max we do is link_reset in ERR_FATAL case, and Secondary bus reset
> should affect downstream components (not upstream)

Our first generation controller had this problem. There could be others 
too.