Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII;
 format=flowed
Content-Transfer-Encoding: 7bit
Date:   Mon, 11 Jun 2018 18:20:29 +0530
From:   poza@codeaurora.org
To:     Bjorn Helgaas <helgaas@kernel.org>
Cc:     Bjorn Helgaas <bhelgaas@google.com>,
        Philippe Ombredanne <pombredanne@nexb.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        Dongdong Liu <liudongdong3@huawei.com>,
        Keith Busch <keith.busch@intel.com>, Wei Zhang <wzhang@fb.com>,
        Sinan Kaya <okaya@codeaurora.org>,
        Timur Tabi <timur@codeaurora.org>,
        linux-pci-owner@vger.kernel.org
Subject: Re: [PATCH NEXT 6/6] PCI/PORTDRV: Remove ERR_FATAL handling from
 pcie_portdrv_slot_reset()
In-Reply-To: <50f38cb058b29f84ca60a19825efd28a@codeaurora.org>
References: <1528351234-26914-1-git-send-email-poza@codeaurora.org>
 <1528351234-26914-6-git-send-email-poza@codeaurora.org>
 <94661add3e71e3694aa22c2a9cabf503@codeaurora.org>
 <20180607213448.GB37077@bhelgaas-glaptop.roam.corp.google.com>
 <50f38cb058b29f84ca60a19825efd28a@codeaurora.org>
Message-ID: <c079ffe5ac8e0504eea3efb71a056b94@codeaurora.org>
User-Agent: Roundcube Webmail/1.2.5
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2018-06-11 15:31, poza@codeaurora.org wrote:
> On 2018-06-08 03:04, Bjorn Helgaas wrote:
>> On Thu, Jun 07, 2018 at 07:18:03PM +0530, poza@codeaurora.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@codeaurora.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.
> 
> Hi Bjorn and Keith,
> 
> broadcast_error_message()
> if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
>         .....
>         pci_walk_bus(dev->subordinate, cb, &result_data);
> 
> 
> so in case of ERR_FATAL, the walk bus is happening on subordinates,
> and if I understand the walk right
> then, pcie_portdrv_slot_reset() is called only on BRIDGES/Switches
> 
> If is never called on Root-Ports
> 
> having said that, now since we are removing the devices (compare to
> previous error callback handling in ERR_FATAL)
> I dont see the need of the above code anymore.
> 

when I say above code, I meant this patch itself which removes ERR_FATAL 
handling out of pcie_portdrv_slot_reset

> because there is nothing to restore to any more. as we are initiating
> re-enumeration.
> 
> Regards,
> Oza.