From: "Zhao, Haifeng" <email@example.com> To: "Kuppuswamy, Sathyanarayanan" <firstname.lastname@example.org>, Lukas Wunner <email@example.com>, Bjorn Helgaas <firstname.lastname@example.org>, "Williams, Dan J" <email@example.com> Cc: Sinan Kaya <firstname.lastname@example.org>, "Raj, Ashok" <email@example.com>, "Keith Busch" <firstname.lastname@example.org>, "email@example.com" <firstname.lastname@example.org>, Russell Currey <email@example.com>, "Oliver O'Halloran" <firstname.lastname@example.org>, Stuart Hayes <email@example.com>, Mika Westerberg <firstname.lastname@example.org> Subject: RE: [PATCH] PCI: pciehp: Ignore Link Down/Up caused by DPC Date: Wed, 28 Apr 2021 01:42:12 +0000 [thread overview] Message-ID: <MWHPR11MB1982F7F0B3C1FAB941284C4597409@MWHPR11MB1982.namprd11.prod.outlook.com> (raw) In-Reply-To: <email@example.com> I thought it would be merged into 5.12 release. A little disappointed :< , What can I do to help ? Thanks, Etan -----Original Message----- From: Kuppuswamy, Sathyanarayanan <firstname.lastname@example.org> Sent: Wednesday, April 28, 2021 8:40 AM To: Lukas Wunner <email@example.com>; Bjorn Helgaas <firstname.lastname@example.org>; Williams, Dan J <email@example.com> Cc: Zhao, Haifeng <firstname.lastname@example.org>; Sinan Kaya <email@example.com>; Raj, Ashok <firstname.lastname@example.org>; Keith Busch <email@example.com>; firstname.lastname@example.org; Russell Currey <email@example.com>; Oliver O'Halloran <firstname.lastname@example.org>; Stuart Hayes <email@example.com>; Mika Westerberg <firstname.lastname@example.org> Subject: Re: [PATCH] PCI: pciehp: Ignore Link Down/Up caused by DPC Hi Bjorn, On 3/30/21 1:53 PM, Kuppuswamy, Sathyanarayanan wrote: >> Downstream Port Containment (PCIe Base Spec, sec. 6.2.10) disables >> the link upon an error and attempts to re-enable it when instructed >> by the DPC driver. >> >> A slot which is both DPC- and hotplug-capable is currently brought >> down by pciehp once DPC is triggered (due to the link change) and >> brought up on successful recovery. That's undesirable, the slot >> should remain up so that the hotplugged device remains bound to its >> driver. DPC notifies the driver of the error and of successful >> recovery in pcie_do_recovery() and the driver may then restore the device to working state. >> >> Moreover, Sinan points out that turning off slot power by pciehp may >> foil recovery by DPC: Power off/on is a cold reset concurrently to >> DPC's warm reset. Sathyanarayanan reports extended delays or failure >> in link retraining by DPC if pciehp brings down the slot. >> >> Fix by detecting whether a Link Down event is caused by DPC and >> awaiting recovery if so. On successful recovery, ignore both the >> Link Down and the subsequent Link Up event. >> >> Afterwards, check whether the link is down to detect surprise-removal >> or another DPC event immediately after DPC recovery. Ensure that the >> corresponding DLLSC event is not ignored by synthesizing it and >> invoking irq_wake_thread() to trigger a re-run of pciehp_ist(). >> >> The IRQ threads of the hotplug and DPC drivers, pciehp_ist() and >> dpc_handler(), race against each other. If pciehp is faster than >> DPC, it will wait until DPC recovery completes. >> >> Recovery consists of two steps: The first step (waiting for link >> disablement) is recognizable by pciehp through a set DPC Trigger >> Status bit. The second step (waiting for link retraining) is >> recognizable through a newly introduced PCI_DPC_RECOVERING flag. >> >> If DPC is faster than pciehp, neither of the two flags will be set >> and pciehp may glean the recovery status from the new PCI_DPC_RECOVERED flag. >> The flag is zero if DPC didn't occur at all, hence DLLSC events are >> not ignored by default. >> >> This commit draws inspiration from previous attempts to synchronize >> DPC with pciehp: >> >> By Sinan Kaya, August 2018: >> https://lore.kernel.org/linux-pci/20180818065126.77912-1-okaya@kernel >> .org/ >> >> By Ethan Zhao, October 2020: >> https://lore.kernel.org/linux-pci/20201007113158.48933-1-haifeng.zhao >> @intel.com/ >> >> By Sathyanarayanan Kuppuswamy, March 2021: >> https://lore.kernel.org/linux-pci/59cb30f5e5ac6d65427ceaadf1012b2ba8d >> email@example.com/ >> > Looks good to me. This patch fixes the reported issue in our environment. > > Reviewed-by: Kuppuswamy Sathyanarayanan > <firstname.lastname@example.org> > Tested-by: Kuppuswamy Sathyanarayanan > <email@example.com> Any update on this patch? is this queued for merge? One of our customers is looking for this fix. So wondering about the status. -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
next prev parent reply other threads:[~2021-04-28 1:42 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-28 8:52 Lukas Wunner 2021-03-30 20:53 ` Kuppuswamy, Sathyanarayanan 2021-04-28 0:39 ` Kuppuswamy, Sathyanarayanan 2021-04-28 1:42 ` Zhao, Haifeng [this message] 2021-04-28 10:08 ` Yicong Yang 2021-04-28 14:40 ` Lukas Wunner 2021-04-29 11:29 ` Yicong Yang 2021-04-29 12:40 ` Zhao, Haifeng 2021-04-29 19:42 ` Lukas Wunner 2021-04-30 8:47 ` Yicong Yang 2021-04-30 12:15 ` Lukas Wunner 2021-04-29 19:36 ` Keith Busch 2021-04-29 20:16 ` Lukas Wunner 2021-04-29 21:16 ` Keith Busch
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