Messages in this thread | | | Date | Thu, 3 Feb 2022 14:38:33 -0600 | From | Bjorn Helgaas <> | Subject | Re: [PATCH] PCI: pciehp: clear cmd_busy bit when Command Completed in polling mode |
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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@linux.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@linux.alibaba.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Lukas Wunner <lukas@wunner.de> Cc: stable@vger.kernel.org # v4.19+
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