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Message-ID: <20220203203833.GA113163@bhelgaas>
Date: Thu, 3 Feb 2022 14:38:33 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Lukas Wunner <lukas@...ner.de>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
Liguang Zhang <zhangliguang@...ux.alibaba.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
Amey Narkhede <ameynarkhede03@...il.com>,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: pciehp: clear cmd_busy bit when Command Completed
in polling mode
On Thu, Feb 03, 2022 at 08:07:31PM +0100, Lukas Wunner wrote:
> Hi Bjorn,
>
> the below patch is marked "Changes Requested" in patchwork:
>
> https://patchwork.kernel.org/project/linux-pci/patch/20211111054258.7309-1-zhangliguang@linux.alibaba.com/
>
> I think that might be erroneous because the patch is correct,
> I've provided a Reviewed-by and no change requests are recorded
> in patchwork or the mailing list archive.
>
> If you've got a few minutes to spare, could you double-check the
> state in patchwork and provide Liguang Zhang with the changes you'd
> want (if any)?
Thanks for reminding me about this. I don't remember why I marked it
"changes requested" but I often do that if there's been significant
discussion. In this case you also provided additional information
(Fixes tag, bugzilla link, commit log elaboration) that should be
included. Given that, I would typically wait for the author to repost
it and incorporate the additional information.
But I applied it to pci/hotplug with the commit log below.
commit 92912b175178 ("PCI: pciehp: Clear cmd_busy bit in polling mode")
Author: Liguang Zhang <zhangliguang@...ux.alibaba.com>
Date: Thu Nov 11 13:42:58 2021 +0800
PCI: pciehp: Clear cmd_busy bit in polling mode
Writes to a Downstream Port's Slot Control register are PCIe hotplug
"commands." If the Port supports Command Completed events, software must
wait for a command to complete before writing to Slot Control again.
pcie_do_write_cmd() sets ctrl->cmd_busy when it writes to Slot Control. If
software notification is enabled, i.e., PCI_EXP_SLTCTL_HPIE and
PCI_EXP_SLTCTL_CCIE are set, ctrl->cmd_busy is cleared by pciehp_isr().
But when software notification is disabled, as it is when pcie_init()
powers off an empty slot, pcie_wait_cmd() uses pcie_poll_cmd() to poll for
command completion, and it neglects to clear ctrl->cmd_busy, which leads to
spurious timeouts:
pcieport 0000:00:03.0: pciehp: Timeout on hotplug command 0x01c0 (issued 2264 msec ago)
pcieport 0000:00:03.0: pciehp: Timeout on hotplug command 0x05c0 (issued 2288 msec ago)
Clear ctrl->cmd_busy in pcie_poll_cmd() when it detects a Command Completed
event (PCI_EXP_SLTSTA_CC).
[bhelgaas: commit log]
Fixes: a5dd4b4b0570 ("PCI: pciehp: Wait for hotplug command completion where necessary")
Link: https://lore.kernel.org/r/20211111054258.7309-1-zhangliguang@linux.alibaba.com
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215143
Link: https://lore.kernel.org/r/20211126173309.GA12255@wunner.de
Signed-off-by: Liguang Zhang <zhangliguang@...ux.alibaba.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Reviewed-by: Lukas Wunner <lukas@...ner.de>
Cc: stable@...r.kernel.org # v4.19+
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