linux-kernel - Re: [PATCH v2 1/2] PCI/portdrv: Add necessary wait for disabling hotplug events

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Message-ID: <Z7W8tlhd-Yw3snk4@U-2FWC9VHC-2323.local>
Date: Wed, 19 Feb 2025 19:12:54 +0800
From: Feng Tang <feng.tang@...ux.alibaba.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, Lukas Wunner <lukas@...ner.de>,
	Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Liguang Zhang <zhangliguang@...ux.alibaba.com>,
	Guanghui Feng <guanghuifeng@...ux.alibaba.com>, rafael@...nel.org,
	Markus Elfring <Markus.Elfring@....de>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	ilpo.jarvinen@...ux.intel.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] PCI/portdrv: Add necessary wait for disabling
 hotplug events

On Wed, Feb 19, 2025 at 10:53:44AM +0800, Feng Tang wrote:
[...] 
> > 
> > And IIUC this will add a one second delay for ports that don't need
> > command completed events.  I don't think that's fair to those ports.
> 
> Good catch! So we should add a read of PCI_EXP_SLTCAP register and
> check if PCI_EXP_SLTCAP_HPC bit is set.

Maybe something like this?

	if (slot_cap & PCI_EXP_SLTCAP_HPC &&
	    !(slot_cap & PCI_EXP_SLTCAP_NCCS) &&
	    !pdev->broken_cmd_compl)
	    do_the_wait();

Thanks,
Feng