linux-kernel - Re: [PATCH 1/4] PCI: pciehp: Clean up debug logging

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Message-ID: <1650350.VG8hpWuxzd@vostro.rjw.lan>
Date:	Thu, 18 Jun 2015 23:52:49 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Rajat Jain <rajatja@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] PCI: pciehp: Clean up debug logging

On Thursday, June 18, 2015 04:22:53 PM Bjorn Helgaas wrote:
> [+cc Rafael]
> 
> On Thu, Jun 18, 2015 at 1:08 PM, Rajat Jain <rajatja@...gle.com> wrote:
> > On Thu, Jun 18, 2015 at 11:01 AM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> >> On Thu, Jun 18, 2015 at 12:27 PM, Rajat Jain <rajatja@...gle.com> wrote:
> >>> Hi,
> >>>
> >>> On Thu, Jun 18, 2015 at 9:12 AM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> >>>> The pciehp debug logging is overly verbose and often redundant.  Almost all
> >>>> of the information printed by dbg_ctrl() is also printed by the normal PCI
> >>>> core enumeration code and by pcie_init().
> >>>>
> >>>> Remove the redundant debug info.
> >>>>
> >>>> When claiming a pciehp bridge, we print the slot characteristics, e.g.,
> >>>>
> >>>>   Slot #6 AttnBtn- AttnInd- PwrInd- PwrCtrl- MRL- Interlock- NoCompl+ LLActRep+
> >>>>
> >>>> Add the Hot-Plug Capable and Hot-Plug Surprise bits to this information,
> >>>
> >>> If the slot is not hotplug capable. then pciehp wouldn't claim it in
> >>> the first place.
> >>>
> >>> So printing of "hotplug capable" may really not be needed..
> >>
> >> Yes, I did think about that, and you're right that it probably isn't
> >> needed.  But the criteria for claiming a slot and deciding whether
> >> acpiphp or pciehp should manage it are not 100% clear yet, so I
> >> figured it wouldn't hurt to be a bit more transparent.
> >
> > Sounds right.
> >
> > Reviewed-by : Rajat Jain <rajatja@...gle.com>
> >
> > Side note: To clarify when and why the slot was claimed by pciehp or
> > acpihp, do you think we need some mumbling / logging in
> > acpi_pci_detect_ejectable() or pciehp_acpi_slot_detection_check()?
> 
> Maybe so (but I haven't added anything).
> 
> My intuition is that acpiphp and pciehp are not really symmetric.  I
> think pciehp should claim PCIe downstream ports (Root Ports and
> Downstream Ports) when _OSC has granted us control.
> 
> But it doesn't seem like acpiphp should decide whether to claim
> certain devices based on whether they have _ADR, _EJ0, _RMV, etc.

But it doesn't do that, does it?

> Shouldn't it just be integrated with the ACPI core so  it can field
> notifications from the platform, no matter what methods are present,
> and even if pciehp has claimed a bridge in that scope?

That's how it is implemented today AFAICS.

Thanks,
Rafael

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