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

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Date: Mon, 17 Jun 2024 11:31:06 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Songyang Li <leesongyang@...look.com>
Cc: bhelgaas@...gle.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, Jun 17, 2024 at 09:35:20PM +0800, Songyang Li 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!

Thanks,
  Bjorn