linux-kernel - Re: [PATCH] PCI: Cancel compilation restrictions on function pcie_clear_device

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Date: Sun, 23 Jun 2024 11:28:27 +0800
From: Songyang Li <leesongyang@...look.com>
To: helgaas@...nel.org
Cc: bhelgaas@...gle.com,
	leesongyang@...look.com,
	linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] PCI: Cancel compilation restrictions on function pcie_clear_device_status

On Mon, 17 Jun 2024 11:31:06 -0500, Bjorn Helgaas wrote:
>> On Sat, 15 Jun 2024 16:26:03 -0500, Bjorn Helgaas wrote:
>> > > On Wed, 12 Jun 2024 15:14:32 -0500, Bjorn Helgaas wrote:
>> > > > I think all current any callers of pcie_clear_device_status() are also
>> > > > under CONFIG_PCIEAER, so I don't think this fixes a current problem.
>> > > > 
>> > > > As you point out, it might make sense to use
>> > > > pcie_clear_device_status() even without AER, but I think we should
>> > > > include this change at the time when we add such a use.
>> > > > 
>> > > > If I'm missing a use with the current kernel, let me know.
>> > > 
>> > > As far as I know, some PCIe device drivers, for example,
>> > > [net/ethernet/broadcom/tg3.c],[net/ethernet/atheros/atl1c/atl1c_main.c],
>> > > which use the following code to clear the device status register,
>> > > pcie_capability_write_word(tp->pdev, PCI_EXP_DEVSTA,
>> > >                 PCI_EXP_DEVSTA_CED |
>> > >                 PCI_EXP_DEVSTA_NFED |
>> > >                 PCI_EXP_DEVSTA_FED |
>> > >                 PCI_EXP_DEVSTA_URD);
>> > > I think it may be more suitable to export the pcie_clear_device_status()
>> > > for use in the driver code.
>> > 
>> > If we want to use this from drivers, it would make sense to do
>> > something like this patch, and this patch could be part of a series to
>> > call it from the drivers.
>> > 
>> > But at the same time, we should ask whether drivers should be clearing
>> > this status themselves, or whether it should be done by the PCI core.
>> 
>> After careful consideration, I agree with your point of view.
>> I hold a viewpoint that it should be done by the PCI core,
>> rather than pcie drivers. I give up this patch, and then I have
>> gained a profound understanding of PCIe Core from this communication.
>
>I tend to think this should be done by the PCI core, but I haven't
>looked at it enough to know how or where.  If you pursue it, I'd love
>to see your ideas!

I have used the device status regs of PCIe as the basis for error detection,
which is used for PCIe devices without AER capability. But the current
solution is not universal and I look forward to submitting to the
community in the future.

Songyang Li