From: Bjorn Helgaas <helgaas@kernel.org>
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: Austin.Bolen@dell.com, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org, ashok.raj@intel.com
Subject: Re: [PATCH v17 09/12] PCI/AER: Allow clearing Error Status Register in FF mode
Date: Thu, 12 Mar 2020 17:32:22 -0500 [thread overview]
Message-ID: <20200312223222.GA200236@google.com> (raw)
In-Reply-To: <951fc29a-1462-ef46-d9a2-5e1cd50bf90a@linux.intel.com>
On Thu, Mar 12, 2020 at 02:59:15PM -0700, Kuppuswamy Sathyanarayanan wrote:
> Hi Bjorn,
>
> On 3/12/20 12:53 PM, Bjorn Helgaas wrote:
> > On Wed, Mar 11, 2020 at 04:07:59PM -0700, Kuppuswamy Sathyanarayanan wrote:
> > > On 3/11/20 3:23 PM, Bjorn Helgaas wrote:
> > > > Is any synchronization needed here between the EDR path and the
> > > > hotplug/enumeration path?
> > > If we want to follow the implementation note step by step (in
> > > sequence) then we need some synchronization between EDR path and
> > > enumeration path. But if it's OK to achieve the same end result by
> > > following steps out of sequence then we don't need to create any
> > > dependency between EDR and enumeration paths. Currently we follow
> > > the latter approach.
> > What would the synchronization look like?
> we might need some way to disable the enumeration path till
> we get response from firmware.
>
> In native hot plug case, I think we can do it in two ways.
>
> 1. Disable hotplug notification in slot ctl registers.
> (pcie_disable_notification())
> 2. Some how block hotplug driver from processing the new
> events (not sure how feasible its).
>
> Following method 1 would be easy, But I am not sure whether
> its alright to disable them randomly. I think, unless we
> clear the status as well, we might get some issues due to stale
> notification history.
>
> For ACPI event case, I am not sure whether we have some
> communication protocol in place to disable receiving ACPI
> events temporarily.
>
> For polling model, we need to disable to the polling
> timer thread till we receive _OST response from firmware.
> >
> > Ideally I think it would be better to follow the order in the
> > flowchart if it's not too onerous.
> None of the above changes will be pretty and I think it will
> not be simple as well.
> > That will make the code easier to
> > understand. The current situation with this dependency on pciehp and
> > what it will do leaves a lot of things implicit.
> >
> > What happens if CONFIG_PCIE_EDR=y but CONFIG_HOTPLUG_PCI_PCIE=n?
> >
> > IIUC, when DPC triggers, pciehp is what fields the DLLSC interrupt and
> > unbinds the drivers and removes the devices.
>
> > If that doesn't happen, and Linux clears the DPC trigger to bring
> > the link back up, will those drivers try to operate uninitialized
> > devices?
>
> I don't think this will happen. In DPC reset_link before we bring up
> the device we wait for link to go down first using
> pcie_wait_for_link(pdev, false) function.
I understand that, but these child devices were reset when DPC
disabled the link. When the link comes back up, their BARs contain
zeros.
If CONFIG_HOTPLUG_PCI_PCIE=y, the DLLSC interrupt will cause pciehp to
unbind the driver. It seems like the unbind races with the EDR notify
handler. If pciehp unbinds the driver before edr_handle_event() calls
pcie_do_recovery(), this seems fine -- we'll call dpc_reset_link(),
which brings up the link, we won't call any driver callbacks because
there's no driver, and another DLLSC interrupt will cause pciehp to
re-enumerate, which will re-initialize the device, then rebind the
driver.
If the EDR notify handler runs before pciehp unbinds the driver,
couldn't EDR bring up the link and call driver .mmio_enabled() before
the device has been initialized?
If CONFIG_HOTPLUG_PCI_PCIE=n and CONFIG_HOTPLUG_PCI_ACPI=y, I could
believe that the situations are similar to the above.
What if CONFIG_HOTPLUG_PCI_PCIE=n and CONFIG_HOTPLUG_PCI_ACPI=n? Then
I assume there's nothing to unbind the driver, so pcie_do_recovery()
will call the driver .mmio_enabled() and other recovery callbacks on a
device that hasn't been initialized?
next prev parent reply other threads:[~2020-03-12 22:32 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-04 2:36 [PATCH v17 00/12] Add Error Disconnect Recover (EDR) support sathyanarayanan.kuppuswamy
2020-03-04 2:36 ` [PATCH v17 01/12] PCI/ERR: Update error status after reset_link() sathyanarayanan.kuppuswamy
2020-03-04 2:36 ` [PATCH v17 02/12] PCI/AER: Move pci_cleanup_aer_error_status_regs() declaration to pci.h sathyanarayanan.kuppuswamy
2020-03-04 2:36 ` [PATCH v17 03/12] PCI/ERR: Remove service dependency in pcie_do_recovery() sathyanarayanan.kuppuswamy
2020-03-17 14:40 ` Christoph Hellwig
2020-03-04 2:36 ` [PATCH v17 04/12] PCI: portdrv: remove unnecessary pcie_port_find_service() sathyanarayanan.kuppuswamy
2020-03-04 2:36 ` [PATCH v17 05/12] PCI: portdrv: remove reset_link member from pcie_port_service_driver sathyanarayanan.kuppuswamy
2020-03-17 14:41 ` Christoph Hellwig
2020-03-17 14:55 ` Kuppuswamy, Sathyanarayanan
2020-03-04 2:36 ` [PATCH v17 06/12] Documentation: PCI: Remove reset_link references sathyanarayanan.kuppuswamy
2020-03-17 14:42 ` Christoph Hellwig
2020-03-17 15:05 ` Kuppuswamy, Sathyanarayanan
2020-03-17 15:07 ` Christoph Hellwig
2020-03-17 16:03 ` Bjorn Helgaas
2020-03-17 17:06 ` Christoph Hellwig
2020-03-19 22:52 ` Bjorn Helgaas
2020-03-04 2:36 ` [PATCH v17 07/12] PCI/ERR: Return status of pcie_do_recovery() sathyanarayanan.kuppuswamy
2020-03-04 2:36 ` [PATCH v17 08/12] PCI/DPC: Cache DPC capabilities in pci_init_capabilities() sathyanarayanan.kuppuswamy
2020-03-04 2:36 ` [PATCH v17 09/12] PCI/AER: Allow clearing Error Status Register in FF mode sathyanarayanan.kuppuswamy
2020-03-06 5:45 ` Kuppuswamy, Sathyanarayanan
2020-03-06 16:04 ` Bjorn Helgaas
2020-03-06 16:11 ` Kuppuswamy, Sathyanarayanan
2020-03-06 16:41 ` Bjorn Helgaas
2020-03-10 2:40 ` Bjorn Helgaas
2020-03-10 4:28 ` Kuppuswamy, Sathyanarayanan
2020-03-10 18:14 ` Austin.Bolen
2020-03-10 19:32 ` Bjorn Helgaas
2020-03-10 20:06 ` Austin.Bolen
2020-03-10 20:41 ` Kuppuswamy Sathyanarayanan
2020-03-10 20:49 ` Austin.Bolen
2020-03-11 14:45 ` Bjorn Helgaas
2020-03-11 15:19 ` Austin.Bolen
2020-03-11 17:12 ` Bjorn Helgaas
2020-03-11 17:27 ` Austin.Bolen
2020-03-11 20:33 ` Bjorn Helgaas
2020-03-11 21:25 ` Kuppuswamy Sathyanarayanan
2020-03-11 21:53 ` Austin.Bolen
2020-03-11 22:11 ` Kuppuswamy Sathyanarayanan
2020-03-11 22:23 ` Bjorn Helgaas
2020-03-11 23:07 ` Kuppuswamy Sathyanarayanan
2020-03-12 19:53 ` Bjorn Helgaas
2020-03-12 21:02 ` Austin.Bolen
2020-03-12 21:29 ` Kuppuswamy Sathyanarayanan
2020-03-12 21:52 ` Bjorn Helgaas
2020-03-12 22:02 ` Kuppuswamy Sathyanarayanan
2020-03-12 22:36 ` Bjorn Helgaas
2020-03-12 21:59 ` Kuppuswamy Sathyanarayanan
2020-03-12 22:32 ` Bjorn Helgaas [this message]
2020-03-13 6:22 ` Kuppuswamy, Sathyanarayanan
2020-03-13 19:28 ` Bjorn Helgaas
2020-03-13 20:26 ` Kuppuswamy Sathyanarayanan
2020-03-19 23:03 ` Bjorn Helgaas
2020-03-19 23:20 ` Kuppuswamy, Sathyanarayanan
2020-03-11 22:13 ` Bjorn Helgaas
2020-03-11 22:41 ` Kuppuswamy Sathyanarayanan
2020-03-11 18:12 ` Kuppuswamy Sathyanarayanan
2020-03-11 22:05 ` Bjorn Helgaas
2020-03-04 2:36 ` [PATCH v17 10/12] PCI/DPC: Export DPC error recovery functions sathyanarayanan.kuppuswamy
2020-03-17 14:43 ` Christoph Hellwig
2020-03-04 2:36 ` [PATCH v17 11/12] PCI/DPC: Add Error Disconnect Recover (EDR) support sathyanarayanan.kuppuswamy
2020-03-06 3:47 ` Bjorn Helgaas
2020-03-06 6:32 ` Kuppuswamy, Sathyanarayanan
2020-03-06 21:00 ` Bjorn Helgaas
2020-03-06 22:42 ` Kuppuswamy Sathyanarayanan
2020-03-06 23:23 ` Bjorn Helgaas
2020-03-07 0:19 ` Kuppuswamy Sathyanarayanan
2020-03-04 2:36 ` [PATCH v17 12/12] PCI/ACPI: Enable EDR support sathyanarayanan.kuppuswamy
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