[Fwd: Re: [PATCH 4/5]PCI: x86 MMCONFIG: introduce pcibios_fix_bus_scan()]

[Tony Camuso <tcamuso@redhat.com>]

-------- Original Message --------
Subject: Re: [PATCH 4/5]PCI: x86 MMCONFIG: introduce pcibios_fix_bus_scan()
Date: Wed, 19 Dec 2007 19:17:42 -0500
From: Tony Camuso <tcamuso@redhat.com>
Reply-To: tcamuso@redhat.com
To: Greg KH <gregkh@suse.de>
References: 
<20071219221746.20362.39243.sendpatchset@dhcp83-188.boston.redhat.com> 
<20071219221806.20362.25964.sendpatchset@dhcp83-188.boston.redhat.com> 
<20071219231032.GC24219@suse.de>

Greg,

First, let me thank you for your prompt replies!

Greg KH wrote:
> On Wed, Dec 19, 2007 at 05:18:06PM -0500, tcamuso@redhat.com wrote:
> > commit ab28e1157e970f711c8451b66b3f940ec092db9d
> > Author: Tony Camuso <tony.camuso@hp.com>
> > Date:   Wed Dec 19 15:51:48 2007 -0500
> >
> >     Introduces the x86 arch-specific routine that will determine whether
> >     a device responds correctly to MMCONFIG accesses. This routine is
> >     given the generic name pcibios_fix_bus_scan_quirk()
> >     
> >     The comment at the top of the routine explains its logic.
> >     
> >     Signed-off-by: Tony Camuso tony.camuso@hp.com
> >
> > diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
> > index 8627463..9b1742d 100644
> > --- a/arch/x86/pci/common.c
> > +++ b/arch/x86/pci/common.c
> > @@ -525,3 +525,64 @@ struct pci_bus *pci_scan_bus_with_sysdata(int busno)
> >  
> >  	return bus;
> >  }
> > +
> > +/**
> > + * This routine traps devices not correctly responding to MMCONFIG access.
> > + * For each device on the current bus, compare a mmconf read of the
> > + * vendor/device dword with a legacy PCI config read. If they're not the same,
> > + * the bus serving this device must use legacy PCI config accesses instead of
> > + * mmconf, as must all buses descending from this bus.
> > + */
> > +
> > +#define CHECK_MMCFG_STR_1 \
> > +	"PCI: Device at %04x:%02x.%02x.%x is not MMCONFIG compliant.\n"
> > +#define CHECK_MMCFG_STR_2 \
> > +	"PCI: Bus %04x:%02x and its descendents cannot use MMCONFIG.\n"
>
> Why define these if they are only used in one place?

If you object, I will be happy to move them into the routine body
without the defines. I agree that It does look inconsistent to have
these strings defined and other strings embedded in the routine body.

> Also, as you use dev_info(), I think you are duplicating some of the
> information in the resulting printk(), right?
Actually, no. The strings do not contain redundant info. The pr_info
routine is just a macro for printk(KERN_INFO ...)

> > +
> > +void __devinit pcibios_fix_bus_scan_quirk(struct pci_bus *bus)
> > +{
> > +	int devfn;
> > +	int fail;
> > +	int found_nommconf_dev = 0;
> > +	static int advised;
> > +	u32 mcfg_vendev;
> > +	u32 arch_vendev;
> > +	struct pci_ops *save_ops = bus->ops;
> > +
> > +	if (bus->parent != NULL)
> > +		if (bus->parent->ops == &pci_legacy_ops)
> > +			return;
> > +
> > +	if (!advised) {
> > +		pr_info("PCI: If a device isn't working, try \"pci=nommconf\". "
> > +			"If that helps, please post a report.\n");
>
> Post a report where?  Who is going to handle these reports?
>
> The last time someone put a line like this in the kernel, I got a ton of
> email and didn't know what to do with it.  If you really are trusting of
> this patch, please put your email address in this printk(), so that you
> can properly handle the resulting reports.  I sure don't want to :)

Hmmm! Good point! I was actually copying that other message. I will
remove the string that advises posting a report. I sure don't want 'em,
and I can see that you don't, either.
:)

> > +		advised = 1;
> > +	}
> > +	pr_debug("PCI: Checking bus %04x:%02x for MMCONFIG compliance.\n",
> > +		 pci_domain_nr(bus), bus->number);
> > +
> > +	for (devfn = 0; devfn < 256; devfn++) {
> > +		bus->ops = &pci_legacy_ops;
> > +		fail = (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID,
> > +						  &arch_vendev));
>
> What's with the extra () around the function?

The function call used to be contained in an if statement.
I changed the logic, but forgot to remove the extra parens.
It's tough getting old.
:}

> > +		if ((arch_vendev == 0xFFFFFFFF) || (arch_vendev == 0) || fail)
> > +			continue;
> > +
> > +		bus->ops = save_ops;	/* Restore to original value */
> > +		pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID,
> > +					  &mcfg_vendev);
> > +		if (mcfg_vendev != arch_vendev) {
> > +			found_nommconf_dev = 1;
> > +			break;
> > +		}
> > +	}
> > +
> > +	if (found_nommconf_dev) {
> > +		pr_info(CHECK_MMCFG_STR_1, pci_domain_nr(bus), bus->number,
> > +			PCI_SLOT(devfn), PCI_FUNC(devfn));
> > +		pr_info(CHECK_MMCFG_STR_2, pci_domain_nr(bus), bus->number);
> > +		bus->ops = &pci_legacy_ops;	/* Use Legace PCI Config */
>
> Spelling check for your comments :)
>
> thanks,
>
> greg k-h

Oops Legace ... too much language confusion in my life ... portugues ...
italian ... oi ...


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/