From: Sinan Kaya <okaya@codeaurora.org>
To: Lukas Wunner <lukas@wunner.de>
Cc: linux-pci@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Bjorn Helgaas <bhelgaas@google.com>,
Oza Pawandeep <poza@codeaurora.org>,
Keith Busch <keith.busch@intel.com>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH V5 3/3] PCI: Mask and unmask hotplug interrupts during reset
Date: Tue, 3 Jul 2018 11:43:26 -0400 [thread overview]
Message-ID: <12fc8de5-ff03-cb00-52cb-25a43c71d03a@codeaurora.org> (raw)
In-Reply-To: <20180703143434.GA4086@wunner.de>
On 7/3/2018 10:34 AM, Lukas Wunner wrote:
> On Mon, Jul 02, 2018 at 06:52:47PM -0400, Sinan Kaya wrote:
>> @@ -308,8 +310,17 @@ void pcie_do_fatal_recovery(struct pci_dev *dev, u32 service)
>> pci_dev_put(pdev);
>> }
>>
>> + hpsvc = pcie_port_find_service(udev, PCIE_PORT_SERVICE_HP);
>> + hpdev = pcie_port_find_device(udev, PCIE_PORT_SERVICE_HP);
>> +
>> + if (hpdev && hpsvc)
>> + hpsvc->mask_irq(to_pcie_device(hpdev));
>> +
>> result = reset_link(udev, service);
>>
>> + if (hpdev && hpsvc)
>> + hpsvc->unmask_irq(to_pcie_device(hpdev));
>> +
>
> We've already got the ->reset_slot callback in struct hotplug_slot_ops,
> I'm wondering if we really need additional ones for this use case.
>
> If you just do...
>
> if (!pci_probe_reset_slot(dev->slot))
> pci_reset_slot(dev->slot)
> else {
> /* regular code path */
> }
>
> would that not be equivalent?
As I have informed you before on my previous reply, the pdev->slot is
only valid for children objects such as endpoints not for a bridge when
using pciehp.
The pointer is NULL for the host bridge itself.
I reached out to reset_slot() callback in v4 of this implementation.
https://patchwork.kernel.org/patch/10494971/
However, as Oza explained FATAL error handling gets called from two different
paths as AER and DPC.
If the link goes down due to DPC, calling pci_reset_slot() would be a mistake
as DPC has its own recovery mechanism by programming the DPC capabilities.
pci_reset_slot() performs a secondary bus reset following hotplug interrupt
mask.
Issuing a secondary bus reset to a DPC event would be a mistake for recovery.
That's why, I extracted the hotplug mask and unmask IRQ calls into service
layer so that I can mask hotplug interrupts regardless of the source of the
FATAL error whether it is DPC or AER.
If error source is DPC, it still goes to DPC driver's reset_link() callback
for DPC specific clean up.
If error source is AER, it still goes to AER driver's reset_link() callback
for secondary bus reset.
Remember that AER driver completely bypasses pci_reset_slot() today. The lock
mechanism you are putting will not be useful for FATAL error case where
pci_secondary_bus_reset() is called directly.
pci_reset_slot() only gets called from external drivers such as VFIO to initiate
a reset to the slot if hotplug is supported.
>
> (It's worth noting though that pciehp is the only hotplug driver
> implementing the ->reset_slot callback. If hotplug is handled by
> a different driver or by the platform firmware, devices may still
> be removed and re-enumerated twice.)
>
> Thanks,
>
> Lukas
>
--
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
next prev parent reply other threads:[~2018-07-03 15:43 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1530571967-19099-1-git-send-email-okaya@codeaurora.org>
2018-07-02 22:52 ` [PATCH V5 1/3] PCI: pciehp: implement mask and unmask interrupt functions Sinan Kaya
2018-07-02 22:52 ` [PATCH V5 2/3] PCI: pciehp: reuse pciehp_mask/unmask_irq() in reset_slot() Sinan Kaya
2018-07-02 22:52 ` [PATCH V5 3/3] PCI: Mask and unmask hotplug interrupts during reset Sinan Kaya
2018-07-03 8:34 ` Lukas Wunner
2018-07-03 10:52 ` poza
2018-07-03 12:04 ` okaya
2018-07-03 11:30 ` okaya
2018-07-03 13:11 ` poza
2018-07-03 13:25 ` Sinan Kaya
2018-07-03 13:31 ` Sinan Kaya
2018-07-03 13:59 ` Lukas Wunner
2018-07-03 14:10 ` poza
2018-07-03 14:17 ` Lukas Wunner
2018-07-03 15:34 ` Sinan Kaya
2018-07-29 12:32 ` Lukas Wunner
2018-07-03 14:12 ` Lukas Wunner
2018-07-03 14:29 ` poza
2018-07-29 12:19 ` Lukas Wunner
2018-07-03 14:34 ` Lukas Wunner
2018-07-03 15:12 ` poza
2018-07-03 15:49 ` Sinan Kaya
2018-07-03 15:43 ` Sinan Kaya [this message]
2018-07-08 17:14 ` Lukas Wunner
2018-07-09 14:48 ` Sinan Kaya
2018-07-09 16:00 ` Lukas Wunner
2018-07-10 18:30 ` Sinan Kaya
2018-07-20 20:01 ` Bjorn Helgaas
2018-07-21 2:58 ` Sinan Kaya
2018-07-21 6:07 ` Sinan Kaya
2018-07-25 8:29 ` poza
2018-07-29 18:02 ` Lukas Wunner
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